1
|
Das M, Hogan C, Zielinski R, Kubicki M, Koy M, Kosbab C, Brozzesi S, Das A, Nehring MT, Balfanz V, Brühne J, Dähne M, Franz M, Esser N, Glorius F. N-Heterocyclic Olefins on a Silicon Surface. Angew Chem Int Ed Engl 2023; 62:e202314663. [PMID: 37849449 DOI: 10.1002/anie.202314663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 10/13/2023] [Accepted: 10/17/2023] [Indexed: 10/19/2023]
Abstract
The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips. These different geometries strongly influence the quality and properties of the obtained monolayers. The upright geometry leads to the formation of ordered monolayers, whereas the flat-lying NHOs yield a mostly disordered, but denser, monolayer. The obtained monolayers both show large work function reductions, as the higher density of the flat-lying monolayer is found to compensate for the smaller vertical dipole moments. Our findings offer new prospects in the design of tailor-made ligand structures in organic electronics and optoelectronics, catalysis, and material science.
Collapse
Affiliation(s)
- Mowpriya Das
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Conor Hogan
- Istituto di Struttura della Materia-CNR (ISM-CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
- Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Robert Zielinski
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Milan Kubicki
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Maximilian Koy
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Canan Kosbab
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Simone Brozzesi
- Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Ankita Das
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Mike Thomas Nehring
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Viktoria Balfanz
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Juls Brühne
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Mario Dähne
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Martin Franz
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Norbert Esser
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
- Leibniz-Institut für Analytische Wissenschaften - ISAS e.V., Schwarzschildstrasse 8, 12489, Berlin, Germany
| | - Frank Glorius
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| |
Collapse
|
2
|
|
3
|
Wu N, Kluger R. Rates of competing fluoride elimination and iodination from a thiamin-derived Breslow intermediate. Bioorg Chem 2022; 120:105579. [DOI: 10.1016/j.bioorg.2021.105579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/09/2021] [Accepted: 12/17/2021] [Indexed: 11/02/2022]
|
4
|
Huang GT, Hsieh MH, Yu JSK. Formation of Breslow Intermediates under Aprotic Conditions: A Computational Study. J Org Chem 2022; 87:2501-2507. [PMID: 35029105 DOI: 10.1021/acs.joc.1c02408] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism of formation of the Breslow intermediate (BI) under aprotic conditions is investigated with density functional theory (DFT) calculations. The zwitterionic adduct (ZA) is formed by the first addition of an imidazolinylidene to benzaldehyde. The forward reaction is found to proceed through the second addition of the ZA to another benzaldehyde, and subsequent proton migration gives a hemiacetal. The bimolecular reaction enables the conversion of the ZA to a more reactive hemiacetal, which is further decomposed to the BI with the assistance of the ZA. During the ZA-assisted process, the hemiacetal and the BI act as hydrogen bond donors to stabilize the ZA. The hydrogen bond interactions between the ZA and the BI or hemiacetal are analyzed. The DFT computations demonstrate that along the proposed route, the proton migration leading to the hemiacetal intermediate is the rate-determining step (ΔG⧧ = 21.2 kcal mol-1). The bimolecular mechanism provides an alternative pathway to explain BI formation under aprotic conditions.
Collapse
|
5
|
Fajardo AM, Queyraiux N, Camy A, Vendier L, Grellier M, Del Rosal I, Maron L, Bontemps S. A masked form of an O-borylated Breslow intermediate for the diastereoselective FLP-type activation of aldehydes. Chemistry 2021; 28:e202104122. [PMID: 34964516 DOI: 10.1002/chem.202104122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Indexed: 11/07/2022]
Abstract
Breslow intermediates are very often elusive species whose application in Frustrated Lewis Pair chemistry is unprecedented. We describe herein the use of a masked form of an O-Borylated Breslow (OBB) intermediate that performs FLP-type activation of the carbonyl function of five different benzaldehyde derivatives with complete diastereoselectivity. The resulting compounds are characterised in solution by NMR spectroscopy (compounds 4 - 8 ) and in solid state by X-Ray diffraction analysis (compounds 4 - 6 ). A combined kinetic and theoretical investigation reveals the associative nature of the rate determining step and suggests that the OBB intermediate part is never released during the whole process.
Collapse
Affiliation(s)
| | | | - Aurèle Camy
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Laure Vendier
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Mary Grellier
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Iker Del Rosal
- LPCNO: Laboratoire de physique et chimie des nano-objets, chemistry, FRANCE
| | - Laurent Maron
- LPCNO: Laboratoire de physique et chimie des nano-objets, chemistry, FRANCE
| | - Sébastien Bontemps
- Centre National de la Recherche Scientifique, Laboratoire de Chimie de Coordination, 205 route de Narbonne, 31077 cedex 04, toulouse, FRANCE
| |
Collapse
|
6
|
Cai Z, Zhou J, Yu M, Jiang L. Ag-Catalyzed or Ag/PPh 3-Catalyzed Chemoselective Switchable Cascade Reactions of N-Propargyl Thiocarbamoyl Fluorides and Malonate Esters. Org Lett 2021; 24:293-298. [PMID: 34962811 DOI: 10.1021/acs.orglett.1c03950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The divergent chemoselective synthesis of 2-methylene-2,3-dihydrothiazoles and 4-benzylidene pyrrolidine-2-thiones (most with E stereoselectivity) from N-propargyl thiocarbamoyl fluorides and malonate esters in moderate to excellent yields with a broad substrate scope and functional group tolerance has been accomplished. AgNTf2 catalyst at 60 °C in dichloroethane provided 4-benzylidene pyrrolidine-2-thiones. AgOTf catalyst and PPh3 ligand in refluxing acetonitrile resulted in a complete switch in the reactivity of formed α,α-diester thioamide intermediates followed by isomerization to access 2-methylene-2,3-dihydrothiazoles.
Collapse
Affiliation(s)
- Zhongliang Cai
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Junyi Zhou
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Miao Yu
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Liqin Jiang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| |
Collapse
|
7
|
Collett CJ, Young CM, Massey RS, O'Donoghue AC, Smith AD. Kinetic and Structure‐Activity Studies of the Triazolium Ion‐ Catalyzed Intramolecular Stetter Reaction. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100384] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Christopher J. Collett
- EaStCHEM School of Chemistry University of St. Andrews North Haugh, St. Andrews KY16 9ST UK
| | - Claire M. Young
- EaStCHEM School of Chemistry University of St. Andrews North Haugh, St. Andrews KY16 9ST UK
| | - Richard S. Massey
- Department of Chemistry Durham University South Road Durham DH1 3LE UK
| | | | - Andrew D. Smith
- EaStCHEM School of Chemistry University of St. Andrews North Haugh, St. Andrews KY16 9ST UK
| |
Collapse
|
8
|
Pareek M, Reddi Y, Sunoj RB. Tale of the Breslow intermediate, a central player in N-heterocyclic carbene organocatalysis: then and now. Chem Sci 2021; 12:7973-7992. [PMID: 34194690 PMCID: PMC8208132 DOI: 10.1039/d1sc01910d] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/28/2021] [Indexed: 12/27/2022] Open
Abstract
N-Heterocyclic carbenes (NHCs) belong to the popular family of organocatalysts used in a wide range of reactions, including that for the synthesis of complex natural products and biologically active compounds. In their organocatalytic manifestation, NHCs are known to impart umpolung reactivity to aldehydes and ketones, which are then exploited in the generation of homoenolate, acyl anion, and enolate equivalents suitable for a plethora of reactions such as annulation, benzoin, Stetter, Claisen rearrangement, cycloaddition, and C-C and C-H bond functionalization reactions and so on. A common thread that runs through these NHC catalyzed reactions is the proposed involvement of an enaminol, also known as the Breslow intermediate, formed by the nucleophilic addition of an NHC to a carbonyl group of a suitable electrophile. In the emerging years of NHC catalysis, enaminol remained elusive and was largely considered a putative intermediate owing to the difficulties encountered in its isolation and characterization. However, in the last decade, synergistic efforts utilizing an array of computational and experimental techniques have helped in gaining important insights into the formation and characterization of Breslow intermediates. Computational studies have suggested that a direct 1,2-proton transfer within the initial zwitterionic intermediate, generated by the action of an NHC on the carbonyl carbon, is energetically prohibitive and hence the participation of other species capable of promoting an assisted proton transfer is more likely. The proton transfer assisted by additives (such as acids, bases, other species, or even a solvent) was found to ease the kinetics of formation of Breslow intermediates. These important details on the formation, in situ detection, isolation, and characterization of the Breslow intermediate are scattered over a series of reports spanning well over a decade, and we intend to consolidate them in this review and provide a critical assessment of these developments. Given the central role of the Breslow intermediate in organocatalytic reactions, this treatise is expected to serve as a valuable source of knowledge on the same.
Collapse
Affiliation(s)
- Monika Pareek
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Yernaidu Reddi
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Raghavan B Sunoj
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| |
Collapse
|
9
|
Massey RS, Murray J, Collett CJ, Zhu J, Smith AD, O'Donoghue AC. Kinetic and structure-activity studies of the triazolium ion-catalysed benzoin condensation. Org Biomol Chem 2021; 19:387-393. [PMID: 33351015 DOI: 10.1039/d0ob02207a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Steady-state kinetic and structure-activity studies of a series of six triazolium-ion pre-catalysts 2a-2f were investigated for the benzoin condensation. These data provide quantitative insight into the role of triazolium N-aryl substitution under synthetically relevant catalytic conditions in a polar solvent environment. Kinetic behaviour was significantly different to that previously reported for a related thiazolium-ion pre-catalyst 1, with the observed levelling of initial rate constants to νmax at high aldehyde concentrations for all triazolium catalysts. Values for νmax for 2a-2f increase with electron withdrawing N-aryl substituents, in agreement with reported optimal synthetic outcomes under catalytic conditions, and vary by 75-fold across the series. The levelling of rate constants supports a change in rate-limiting step and evidence supports the assignment of the Breslow-intermediate forming step to the plateau region. Correlation of νmax reaction data yielded a positive Hammett ρ-value (ρ = +1.66) supporting the build up of electron density adjacent to the triazolium N-Ar in the rate-limiting step favoured by electron withdrawing N-aryl substituents. At lower concentrations of aldehyde, both Breslow-intermediate and benzoin formation are partially rate-limiting.
Collapse
Affiliation(s)
- Richard S Massey
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK.
| | - Jacob Murray
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK.
| | - Christopher J Collett
- EaStCHEM, School of Chemistry, University of St. Andrews, North Haugh, St Andrews KY16 9SY, UK
| | - Jiayun Zhu
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK.
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St. Andrews, North Haugh, St Andrews KY16 9SY, UK
| | | |
Collapse
|
10
|
Zhang Z, Huang S, Huang L, Xu X, Zhao H, Yan X. Synthesis of Mesoionic N-Heterocyclic Olefins and Catalytic Application for Hydroboration Reactions. J Org Chem 2020; 85:12036-12043. [DOI: 10.1021/acs.joc.0c00257] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Zengyu Zhang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Shiqing Huang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Linwei Huang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Xingyu Xu
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Hongyan Zhao
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Xiaoyu Yan
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| |
Collapse
|
11
|
Gehrke S, Hollóczki O. N-Heterocyclic Carbene Organocatalysis: With or Without Carbenes? Chemistry 2020; 26:10140-10151. [PMID: 32608090 PMCID: PMC7496998 DOI: 10.1002/chem.202002656] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/26/2020] [Indexed: 11/18/2022]
Abstract
In this work the mechanism of the aldehyde umpolung reactions, catalyzed by azolium cations in the presence of bases, was studied through computational methods. Next to the mechanism established by Breslow in the 1950s that takes effect through the formation of a free carbene, we have suggested that these processes can follow a concerted asynchronous path, in which the azolium cation directly reacts with the substrate, avoiding the formation of the carbene intermediate. We hereby show that substituting the azolium cation, and varying the base or the substrate do not affect the preference for the concerted reaction mechanism. The concerted path was found to exhibit low barriers also for the reactions of thiamine with model substrates, showing that this path might have biological relevance. The dominance of the concerted mechanism can be explained through the specific structure of the key transition state, avoiding the liberation of the highly reactive, and thus unstable carbene lone pair, whereas activating the substrate through hydrogen-bonding interactions. Polar and hydrogen-bonding solvents, as well as the presence of the counterions of the azolium salts facilitate the reaction through carbenes, bringing the barriers of the two reaction mechanisms closer, in many cases making the concerted path less favorable. Thus, our data show that by choosing the exact components in a reaction, the mechanism can be switched to occur with or without carbenes.
Collapse
Affiliation(s)
- Sascha Gehrke
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstr. 4+653115BonnGermany
| | - Oldamur Hollóczki
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstr. 4+653115BonnGermany
| |
Collapse
|
12
|
Hollóczki O. The Mechanism of N-Heterocyclic Carbene Organocatalysis through a Magnifying Glass. Chemistry 2020; 26:4885-4894. [PMID: 31797448 PMCID: PMC7187225 DOI: 10.1002/chem.201903021] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Indexed: 11/11/2022]
Abstract
The term "N-Heterocyclic carbene organocatalysis" is often invoked in organic synthesis for reactions that are catalyzed by different azolium salts in the presence of bases. Although the mechanism of these reactions is considered today evident, a closer look into the details that have been collected throughout the last century reveals that there are many open questions and even contradictions in the field. Emerging new theoretical and experimental results offer solutions to these problems, because they show that through considering alternative reaction mechanisms a more consistent picture on the catalytic process can be obtained. These novel perspectives will be able to extend the scope of the reactions that we call today N-heterocyclic carbene organocatalysis.
Collapse
Affiliation(s)
- Oldamur Hollóczki
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstrasse 4+653115BonnGermany
| |
Collapse
|
13
|
Soeta T, Ukaji Y. Development of Multi-functional NHC Catalysts bearing Pyridine Moiety: Application to Catalytic Asymmetric Reactions. J SYN ORG CHEM JPN 2020. [DOI: 10.5059/yukigoseikyokaishi.78.338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Takahiro Soeta
- Division of Material Chemistry, Graduate School of Natural Science and Technology
| | - Yutaka Ukaji
- Division of Material Chemistry, Graduate School of Natural Science and Technology
| |
Collapse
|
14
|
Kumar J, Rahaman A, Singh AK, Bhadra S. Catalytic Approaches for the Direct Heterofunctionalization of Aliphatic Carboxylic Acids and Their Equivalents with Group 16 Elements. Chem Asian J 2020; 15:673-689. [PMID: 32027467 DOI: 10.1002/asia.201901757] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/27/2020] [Indexed: 11/07/2022]
Abstract
In contrast to traditional multistep synthesis, modern organic synthesis extensively depends on the direct functionalization of unactivated C-H bonds for the construction of various C-C and C-heteroatom bonds in atom- and step-economic manner. Common aliphatic substrates, e. g. carboxylic acids and their synthetic equivalents, are regiospecifically functionalized based on either a directed approach, in which the polar directing group assists to functionalize a specific C-H bond positioned at β- and γ-carbon centers, or a non-directed approach typically leading to α-functionalization. While numerous reviews on catalytic C-H functionalization have appeared, a concise review on the direct C(sp3 )-H heterofunctionalization of carboxylic acid synthons with Group 16 elements has been awaited. The recent advances on the direct oxy-functionalization and chalcogenation of aliphatic carboxylic acid synthons enabled by transition metal, organo- and photocatalysts are described herein.
Collapse
Affiliation(s)
- Jogendra Kumar
- Inorganic Materials and Catalysis Division Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute G. B. Marg, Bhavnagar, 364002, Gujarat, India
| | - Ajijur Rahaman
- Inorganic Materials and Catalysis Division Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute G. B. Marg, Bhavnagar, 364002, Gujarat, India
| | - Anupam Kumar Singh
- Inorganic Materials and Catalysis Division Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute G. B. Marg, Bhavnagar, 364002, Gujarat, India
| | - Sukalyan Bhadra
- Inorganic Materials and Catalysis Division Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute G. B. Marg, Bhavnagar, 364002, Gujarat, India
| |
Collapse
|
15
|
Kumar J, Gupta A, Bhadra S. Pd II-Catalyzed methoxylation of C(sp 3)-H bonds adjacent to benzoxazoles and benzothiazoles. Org Biomol Chem 2019; 17:3314-3318. [PMID: 30860234 DOI: 10.1039/c9ob00337a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The Pd(OAc)2/PhI(OAc)2 catalyst system promotes the highly regioselective dehydrogenative methoxylation of a C(sp3)-H bond adjacent to benzoxazole and benzothiazole rings. The title transformation constitutes the first example of a Pd-catalyzed C(sp3)-H activating methoxylation at the proximal-selective α-position with regard to a directing auxiliary and provides expedient access to an important class of azole-decorated methyl ethers (up to 90% isolated yield). The synthetic practicality of the methodology was demonstrated by achieving α-methoxyacetic acids via the elimination of the benzoxazole auxiliaries and by obtaining the precursor of an O-methylated Breslow intermediate.
Collapse
Affiliation(s)
- Jogendra Kumar
- Inorganic Materials and Catalysis Division, Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute, G.B. Marg, Bhavnagar 364002, Gujarat, India.
| | | | | |
Collapse
|
16
|
Liu W, Zhao LL, Melaimi M, Cao L, Xu X, Bouffard J, Bertrand G, Yan X. Mesoionic Carbene (MIC)-Catalyzed H/D Exchange at Formyl Groups. Chem 2019. [DOI: 10.1016/j.chempr.2019.08.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
17
|
Bielecki M, Howe GW, Kluger R. Competing Protonation and Halide Elimination as a Probe of the Character of Thiamin-Derived Reactive Intermediates. Biochemistry 2019; 58:3566-3571. [PMID: 31385510 DOI: 10.1021/acs.biochem.9b00298] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Decarboxylation reactions from comparable thiamin diphosphate- and thiamin-derived adducts of p-(halomethyl)benzoylformic acids in enzymic and non-enzymic reactions, respectively, reveal critical distinctions in otherwise similar Breslow intermediates. The ratio of protonation to chloride elimination from the Breslow intermediate is 102-fold greater in the enzymic process. This is consistent with a lower intrinsic barrier to proton transfer on the enzyme, implicating formation of a localized tetrahedral (sp3) carbanion that is formed as CO2 is produced. In contrast, slower protonation in solution of the decarboxylated intermediate is consistent with formation of a delocalized planar carbanionic enol/enamine. The proposed structural and reactive character of the enzymic Breslow intermediate is consistent with Warshel's general theory of enzymic catalysis, structural characterization of related intermediates, and the lower kinetic barrier in reactions that occur without changes in hybridization.
Collapse
Affiliation(s)
- Michael Bielecki
- Davenport Chemistry Laboratories, Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada
| | - Graeme W Howe
- Davenport Chemistry Laboratories, Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada
| | - Ronald Kluger
- Davenport Chemistry Laboratories, Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada
| |
Collapse
|
18
|
Nguyen XB, Nakano Y, Duggan NM, Scott L, Breugst M, Lupton DW. N‐Heterocyclic Carbene Catalyzed (5+1) Annulations Exploiting a Vinyl Dianion Synthon Strategy. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905475] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Xuan B. Nguyen
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | | | - Lydia Scott
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Martin Breugst
- Department für Chemie Universität zu Köln Greinstraße 4 50939 Köln Germany
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
19
|
Paul M, Neudörfl JM, Berkessel A. Breslow Intermediates from a Thiazolin-2-ylidene and Fluorinated Aldehydes: XRD and Solution-Phase NMR Spectroscopic Characterization. Angew Chem Int Ed Engl 2019; 58:10596-10600. [PMID: 31131519 DOI: 10.1002/anie.201904308] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/20/2019] [Indexed: 12/20/2022]
Abstract
The first generation and X-ray diffraction (XRD) analysis of a crystalline Breslow intermediate (BI) derived from a thiazolin-2-ylidene, that is, the aromatic heterocycle present in vitamin B1 , is reported. Key to success was the combined use of pentafluorobenzaldehyde and a thiazolin-2-ylidene carrying an enol-stabilizing dispersion energy donor as N-substituent. A so-called primary intermediate (PI) could be isolated in protonated form (pPI) as well and analyzed by XRD. Furthermore, the first stable BI derived from an aromatic thiazolin-2-ylidene and an aliphatic aldehyde (trifluoroacetaldehyde) was prepared and characterized by NMR spectroscopy in solution. When switching to a saturated thiazolidin-2-ylidene, reaction with pentafluorobenzaldehyde afforded a new BI in solution (NMR spectroscopy). Attempts to crystallize the latter BI resulted in the isolation of a novel thiazolidin-2-ylidene dimer that had undergone rearrangement to a hexahydro[1,4]-thiazino[3,2-b]-1,4-thiazine.
Collapse
Affiliation(s)
- Mathias Paul
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
| | - Jörg-M Neudörfl
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
| | - Albrecht Berkessel
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
| |
Collapse
|
20
|
Nguyen XB, Nakano Y, Duggan NM, Scott L, Breugst M, Lupton DW. N‐Heterocyclic Carbene Catalyzed (5+1) Annulations Exploiting a Vinyl Dianion Synthon Strategy. Angew Chem Int Ed Engl 2019; 58:11483-11490. [DOI: 10.1002/anie.201905475] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Indexed: 12/22/2022]
Affiliation(s)
- Xuan B. Nguyen
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | | | - Lydia Scott
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Martin Breugst
- Department für Chemie Universität zu Köln Greinstraße 4 50939 Köln Germany
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
21
|
Paul M, Neudörfl J, Berkessel A. Breslow Intermediates from a Thiazolin‐2‐ylidene and Fluorinated Aldehydes: XRD and Solution‐Phase NMR Spectroscopic Characterization. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201904308] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Mathias Paul
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Jörg‐M. Neudörfl
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
| |
Collapse
|
22
|
Singh T, George A, Parameswaran P, Bharatam PV. Enols, Diamino Enols, and Breslow Intermediates: A Comparative Quantum Chemical Analysis. European J Org Chem 2019. [DOI: 10.1002/ejoc.201801817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tejender Singh
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER), Sector 67; 160 062 S.A.S. Nagar - Punjab India
| | - Anjana George
- Department of Chemistry; National Institute of Technology Calicut; NIT Calicut Campus P.O. 673 601 Kozhikode - Kerala India
| | - Pattiyil Parameswaran
- Department of Chemistry; National Institute of Technology Calicut; NIT Calicut Campus P.O. 673 601 Kozhikode - Kerala India
| | - Prasad V. Bharatam
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER), Sector 67; 160 062 S.A.S. Nagar - Punjab India
| |
Collapse
|
23
|
Xu W, Li Y, Liu R, Yang S, Liu J, Fang X. Kinetic resolution of 2,2-disubstituted-1,3-diketones via carbene catalysis. Org Chem Front 2019. [DOI: 10.1039/c8qo01137k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organocatalytic kinetic resolution of 1,3-diketones with central quaternary stereocenters was achieved for the first time. The resolution proceeds via two basic modes, and the inherent principles between the different combinations of ketone groups and the resolution patterns were also disclosed.
Collapse
Affiliation(s)
- Weici Xu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Yuanzhen Li
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Rui Liu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Shuang Yang
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Jian Liu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Xinqiang Fang
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| |
Collapse
|
24
|
Regnier V, Romero EA, Molton F, Jazzar R, Bertrand G, Martin D. What Are the Radical Intermediates in Oxidative N-Heterocyclic Carbene Organocatalysis? J Am Chem Soc 2018; 141:1109-1117. [PMID: 30561990 DOI: 10.1021/jacs.8b11824] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The oxidation of the Breslow intermediate resulting from the addition of an N-heterocyclic carbene (NHC) to benzaldehyde triggers a fast deprotonation, followed by a second electron transfer, directly affording the corresponding acylium at E > -0.8 V (versus Fc/Fc+). Similarly, the oxidation of the cinnamaldehyde analogue occurs at an even higher potential and is not a reversible electrochemical process. As a whole, and contrary to previous beliefs, it is demonstrated that Breslow intermediates, which are the key intermediates in NHC-catalyzed transformations of aldehydes, cannot undergo a single electron transfer (SET) with mild oxidants ( E < -1.0 V). Moreover, the corresponding enol radical cations are ruled out as relevant intermediates. It is proposed that oxidative NHC-catalyzed radical transformations of enals proceed either through SET from the corresponding electron-rich enolate or through coupled electron-proton transfer from the enol, in any case generating neutral capto-dative radicals. Relevant electrochemical surrogates of these paramagnetic species have been isolated.
Collapse
Affiliation(s)
| | - Erik A Romero
- UMI CNRS 3555, Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0343 , United States
| | - Florian Molton
- Univ. Grenoble Alpes , CNRS, DCM , 38000 Grenoble , France
| | - Rodolphe Jazzar
- UMI CNRS 3555, Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0343 , United States
| | - Guy Bertrand
- UMI CNRS 3555, Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0343 , United States
| | - David Martin
- Univ. Grenoble Alpes , CNRS, DCM , 38000 Grenoble , France
| |
Collapse
|
25
|
Béthegnies A, Escudié Y, Nuñez‐Dallos N, Vendier L, Hurtado J, del Rosal I, Maron L, Bontemps S. Reductive CO2Homocoupling: Synthesis of a Borylated C3Carbohydrate. ChemCatChem 2018. [DOI: 10.1002/cctc.201801875] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Aurélien Béthegnies
- CNRS, LCC (Laboratoire de Chimie de Coordination) 31077 Toulouse (France) andUniversité de Toulouse UPS, INPT Toulouse 31077 France
| | - Yannick Escudié
- CNRS, LCC (Laboratoire de Chimie de Coordination) 31077 Toulouse (France) andUniversité de Toulouse UPS, INPT Toulouse 31077 France
| | - Nelson Nuñez‐Dallos
- CNRS, LCC (Laboratoire de Chimie de Coordination) 31077 Toulouse (France) andUniversité de Toulouse UPS, INPT Toulouse 31077 France
- Department of ChemistryUniversidad de Los Andes Institution Bogotá 111711 Colombia
| | - Laure Vendier
- CNRS, LCC (Laboratoire de Chimie de Coordination) 31077 Toulouse (France) andUniversité de Toulouse UPS, INPT Toulouse 31077 France
| | - John Hurtado
- Department of ChemistryUniversidad de Los Andes Institution Bogotá 111711 Colombia
| | - Iker del Rosal
- Université de Toulouse and CNRS, INSA, UPS, UMR 5215, LPCNO Toulouse F-31077 France
| | - Laurent Maron
- Université de Toulouse and CNRS, INSA, UPS, UMR 5215, LPCNO Toulouse F-31077 France
| | - Sébastien Bontemps
- CNRS, LCC (Laboratoire de Chimie de Coordination) 31077 Toulouse (France) andUniversité de Toulouse UPS, INPT Toulouse 31077 France
| |
Collapse
|
26
|
Scott L, Nakano Y, Zhang C, Lupton DW. Enantioselective N‐Heterocyclic Carbene Catalyzed Cyclopentene Synthesis via the β‐Azolium Ylide. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804271] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Lydia Scott
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Changhe Zhang
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
27
|
Scott L, Nakano Y, Zhang C, Lupton DW. Enantioselective N‐Heterocyclic Carbene Catalyzed Cyclopentene Synthesis via the β‐Azolium Ylide. Angew Chem Int Ed Engl 2018; 57:10299-10303. [DOI: 10.1002/anie.201804271] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/30/2018] [Indexed: 01/04/2023]
Affiliation(s)
- Lydia Scott
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - Changhe Zhang
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
28
|
Nesterov V, Reiter D, Bag P, Frisch P, Holzner R, Porzelt A, Inoue S. NHCs in Main Group Chemistry. Chem Rev 2018; 118:9678-9842. [PMID: 29969239 DOI: 10.1021/acs.chemrev.8b00079] [Citation(s) in RCA: 527] [Impact Index Per Article: 87.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Since the discovery of the first stable N-heterocyclic carbene (NHC) in the beginning of the 1990s, these divalent carbon species have become a common and available class of compounds, which have found numerous applications in academic and industrial research. Their important role as two-electron donor ligands, especially in transition metal chemistry and catalysis, is difficult to overestimate. In the past decade, there has been tremendous research attention given to the chemistry of low-coordinate main group element compounds. Significant progress has been achieved in stabilization and isolation of such species as Lewis acid/base adducts with highly tunable NHC ligands. This has allowed investigation of numerous novel types of compounds with unique electronic structures and opened new opportunities in the rational design of novel organic catalysts and materials. This Review gives a general overview of this research, basic synthetic approaches, key features of NHC-main group element adducts, and might be useful for the broad research community.
Collapse
Affiliation(s)
- Vitaly Nesterov
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Dominik Reiter
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Prasenjit Bag
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Philipp Frisch
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Richard Holzner
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Amelie Porzelt
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Shigeyoshi Inoue
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| |
Collapse
|
29
|
Paul M, Sudkaow P, Wessels A, Schlörer NE, Neudörfl J, Berkessel A. Breslow Intermediates from Aromatic N‐Heterocyclic Carbenes (Benzimidazolin‐2‐ylidenes, Thiazolin‐2‐ylidenes). Angew Chem Int Ed Engl 2018; 57:8310-8315. [PMID: 29645334 DOI: 10.1002/anie.201801676] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Indexed: 12/29/2022]
Affiliation(s)
- Mathias Paul
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Panyapon Sudkaow
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Alina Wessels
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Nils E. Schlörer
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Jörg‐M. Neudörfl
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Cologne UniversityDepartment of Chemistry, Organic Chemistry Greinstrasse 4 50939 Cologne Germany
| |
Collapse
|
30
|
Paul M, Sudkaow P, Wessels A, Schlörer NE, Neudörfl J, Berkessel A. Breslow‐Intermediate aromatischer N‐heterocyclischer Carbene (Benzimidazolin‐2‐ylidene, Thiazolin‐2‐ylidene). Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801676] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Mathias Paul
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| | - Panyapon Sudkaow
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| | - Alina Wessels
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| | - Nils E. Schlörer
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| | - Jörg‐M. Neudörfl
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| | - Albrecht Berkessel
- Universität zu KölnDepartment für ChemieOrganische Chemie Greinstraße 4 50939 Köln Deutschland
| |
Collapse
|
31
|
Ma D, Song Y, Fu C, Zhang F, Guo Y, Huang X, Ma S. E-Selective N-heterocyclic carbene-catalyzed reaction of aldehydes and butadienoates: effect of water and chloroform as the proton shuttle. Org Chem Front 2018. [DOI: 10.1039/c8qo00579f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
An N-heterocyclic carbene-catalyzed reaction of aldehydes and butadienoates affording (E)-4-oxo-2-butenoates highly stereoselectively has been developed. Some key intermediates have been detected by an MS study.
Collapse
Affiliation(s)
- Dengke Ma
- Laboratory of Molecular Recognition and Synthesis
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
- P. R. China
| | - Yulong Song
- Laboratory of Molecular Recognition and Synthesis
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
- P. R. China
| | - Chunling Fu
- Laboratory of Molecular Recognition and Synthesis
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
- P. R. China
| | - Fang Zhang
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032
- P. R. China
| | - Yinlong Guo
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032
- P. R. China
| | - Xin Huang
- Laboratory of Molecular Recognition and Synthesis
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
- P. R. China
| | - Shengming Ma
- Laboratory of Molecular Recognition and Synthesis
- Department of Chemistry
- Zhejiang University
- Hangzhou 310027
- P. R. China
| |
Collapse
|
32
|
Delany EG, Connon SJ. Highly chemoselective intermolecular cross-benzoin reactions using an ad hoc designed novel N-heterocyclic carbene catalyst. Org Biomol Chem 2018; 16:780-786. [DOI: 10.1039/c7ob03005c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new N-heterocyclic carbene catalyst incorporating a bulky yet electron-deficient N-aryl substituent promotes highly chemoselective intermolecular crossed benzoin condensations.
Collapse
Affiliation(s)
- Eoghan G. Delany
- School of Chemistry Trinity Biomedical Sciences Institute
- Trinity College Dublin
- Dublin 2
- Ireland
| | - Stephen J. Connon
- School of Chemistry Trinity Biomedical Sciences Institute
- Trinity College Dublin
- Dublin 2
- Ireland
| |
Collapse
|
33
|
Roy MMD, Rivard E. Pushing Chemical Boundaries with N-Heterocyclic Olefins (NHOs): From Catalysis to Main Group Element Chemistry. Acc Chem Res 2017; 50:2017-2025. [PMID: 28777537 DOI: 10.1021/acs.accounts.7b00264] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
N-Heterocyclic olefins (NHOs) have gone from the topic of a few scattered (but important) reports in the early 1990s to very recently being a ligand/reagent of choice in the far-reaching research fields of organocatalysis, olefin and heterocycle polymerization, and low oxidation state main group element chemistry. NHOs are formally derived by appending an alkylidene (CR2) unit onto an N-heterocyclic carbene (NHC), and their pronounced ylidic character leads to high nucleophilicity and soft Lewis basic character at the ligating carbon atom. These olefinic donors can also be structurally derived from imidazole, triazole, and thiazole-based heterocyclic carbenes and, as a result, have highly tunable electronic and steric properties. In this Account, we will focus on various synthetic routes to imidazole-2-ylidene derived NHOs (sometimes referred to as deoxy-Breslow intermediates) followed by a discussion of the electron-donor ability of this structurally tunable ligand group. It should be mentioned that NHOs have a close structural analogy with Breslow-type intermediates, N-heterocyclic ketene aminals, and β-azolium ylides; while these latter species play important roles in advancing synthetic organic chemistry, discussion in this Account will be confined mostly to imidazole-2-ylidene derived NHOs. In addition, we will cover selected examples from the literature where NHOs and their anionic counterparts, N-heterocyclic vinylenes, are used to access reactive main group species not attainable using traditional ligands. Added motivation for these studies comes from the emerging number of low coordinate main group element based compounds that display reactivity once reserved for precious metal complexes (such as H-H and C-H bond activation). Moreover, NHOs are versatile precursors to new mixed element (P/C and N/C), and potentially bidentate, ligand constructs of great potential in catalysis, where various metal oxidation states and coordination environments need to be stabilized during a catalytic cycle. The most active area of recent growth for NHOs is their use as nucleophiles to promote efficient organocatalytic transformations, including transesterification, carbonyl reduction, and the conversion of CO2 into value added products. Polyesters have also been generated through the NHO-promoted ring-opening polymerization of lactones, and the highly tunable nature of NHO organocatalysts allows for the rapid screening and enhancement of catalytic performance. Therefore, the growing utility of NHOs in the realm of organic and polymer chemistry can be viewed as evidence of the widespread impact of N-heterocyclic olefins on the chemical community. It is hoped that through this Account others will join this flourishing research domain and that the rapid recent growth of NHO chemistry is sustained for the foreseeable future.
Collapse
Affiliation(s)
- Matthew M. D. Roy
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr., Edmonton, Alberta Canada, T6G 2G2
| | - Eric Rivard
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr., Edmonton, Alberta Canada, T6G 2G2
| |
Collapse
|
34
|
Chong CC, Rao B, Ganguly R, Li Y, Kinjo R. Bis(N-heterocyclic olefin) Derivative: An Efficient Precursor for Isophosphindolylium Species. Inorg Chem 2017; 56:8608-8614. [DOI: 10.1021/acs.inorgchem.6b02991] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Che Chang Chong
- Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences, and §NTU-CBC Crystallography
Facility, Nanyang Technological University (NTU), Singapore 637371, Singapore
| | - Bin Rao
- Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences, and §NTU-CBC Crystallography
Facility, Nanyang Technological University (NTU), Singapore 637371, Singapore
| | - Rakesh Ganguly
- Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences, and §NTU-CBC Crystallography
Facility, Nanyang Technological University (NTU), Singapore 637371, Singapore
| | - Yongxin Li
- Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences, and §NTU-CBC Crystallography
Facility, Nanyang Technological University (NTU), Singapore 637371, Singapore
| | - Rei Kinjo
- Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences, and §NTU-CBC Crystallography
Facility, Nanyang Technological University (NTU), Singapore 637371, Singapore
| |
Collapse
|
35
|
Bortolini O, Chiappe C, Fogagnolo M, Massi A, Pomelli CS. Formation, Oxidation, and Fate of the Breslow Intermediate in the N-Heterocyclic Carbene-Catalyzed Aerobic Oxidation of Aldehydes. J Org Chem 2016; 82:302-312. [PMID: 27966944 DOI: 10.1021/acs.joc.6b02414] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction paths and intermediate structures related to the formation of the Breslow intermediate and its oxidation along the oxidative/oxygenative lanes have been studied from a mechanistic point of view, with the support of gas-phase and computational studies. The results confirm the occurrence of a single-electron transfer from the Breslow intermediate to the molecular oxygen with formation of a radical couple that recombines either as a peroxide anion 7' to afford the aldehyde-to-carboxylic acid product or as a hydroperoxy derivative 7″ that evolved into an electrophilic acyl azolium, opening to the aldehyde-to-ester conversion. Steric factors enter into determining the different reactivity. All of the intermediates of both catalytic paths have been observed and characterized under mass spectrometric conditions. In particular, for the imidazoline catalyst, the (+)ESI-MS/(MS) detection of the genuine Breslow intermediate was made possible in virtue of its limited reactivity. Mechanistic aspects of the N-heterocyclic carbenes catalyzed aerobic oxidation of aldehydes shares important similarities with that one of the recently revisited benzoin condensation.
Collapse
Affiliation(s)
- Olga Bortolini
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via Fossato di Mortara 17-19, 44121 Ferrara, Italy
| | - Cinzia Chiappe
- Dipartimento di Farmacia, Università di Pisa , Via Bonanno 33, 56126 Pisa, Italy
| | - Marco Fogagnolo
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via Fossato di Mortara 17-19, 44121 Ferrara, Italy
| | - Alessandro Massi
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via Fossato di Mortara 17-19, 44121 Ferrara, Italy
| | | |
Collapse
|
36
|
Janssen-Müller D, Singha S, Olyschläger T, Daniliuc CG, Glorius F. Annulation of o-Quinodimethanes through N-Heterocyclic Carbene Catalysis for the Synthesis of 1-Isochromanones. Org Lett 2016; 18:4444-7. [DOI: 10.1021/acs.orglett.6b02335] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Daniel Janssen-Müller
- Organisch-Chemisches
Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
| | - Santanu Singha
- Organisch-Chemisches
Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
| | - Theresa Olyschläger
- Organisch-Chemisches
Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
| | - Constantin G. Daniliuc
- Organisch-Chemisches
Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
| | - Frank Glorius
- Organisch-Chemisches
Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
| |
Collapse
|
37
|
Chen X, Fong JZM, Xu J, Mou C, Lu Y, Yang S, Song BA, Chi YR. Carbene-Catalyzed Dynamic Kinetic Resolution of Carboxylic Esters. J Am Chem Soc 2016; 138:7212-5. [DOI: 10.1021/jacs.6b00406] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Xingkuan Chen
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jacqueline Zi Mei Fong
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jianfeng Xu
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chengli Mou
- Laboratory
Breeding Base of Green Pesticide and Agricultural Bioengineering,
Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025, China
| | - Yunpeng Lu
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Song Yang
- Laboratory
Breeding Base of Green Pesticide and Agricultural Bioengineering,
Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025, China
| | - Bao-An Song
- Laboratory
Breeding Base of Green Pesticide and Agricultural Bioengineering,
Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025, China
| | - Yonggui Robin Chi
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- Laboratory
Breeding Base of Green Pesticide and Agricultural Bioengineering,
Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025, China
| |
Collapse
|
38
|
Hong M, Tang X, Falivene L, Caporaso L, Cavallo L, Chen EYX. Proton-Transfer Polymerization by N-Heterocyclic Carbenes: Monomer and Catalyst Scopes and Mechanism for Converting Dimethacrylates into Unsaturated Polyesters. J Am Chem Soc 2016; 138:2021-35. [PMID: 26779897 DOI: 10.1021/jacs.5b13019] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This contribution presents a full account of experimental and theoretical/computational investigations into the N-heterocyclic carbene (NHC)-catalyzed proton-transfer polymerization (HTP) that converts common dimethacrylates (DMAs) containing no protic groups into unsaturated polyesters. This new HTP proceeds through the step-growth propagation cycles via enamine intermediates, consisting of the proposed conjugate addition-proton transfer-NHC release fundamental steps. This study examines the monomer and catalyst scopes as well as the fundamental steps involved in the overall HTP mechanism. DMAs having six different types of linkages connecting the two methacrylates have been polymerized into the corresponding unsaturated polyesters. The most intriguing unsaturated polyester of the series is that based on the biomass-derived furfuryl dimethacrylate, which showed a unique self-curing ability. Four MeO- and Cl-substituted TPT (1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene) derivatives as methanol insertion products, (Rx)TPT(MeO/H) (R = MeO, Cl; x = 2, 3), and two free carbenes (catalysts), (OMe2)TPT and (OMe3)TPT, have been synthesized, while (OMe2)TPT(MeO/H) and (OMe2)TPT have also been structurally characterized. The structure/reactivity relationship study revealed that (OMe2)TPT, being both a strong nucleophile and a good leaving group, exhibits the highest HTP activity and also produced the polyester with the highest Mn, while the Cl-substituted TPT derivatives are least active and efficient. Computational studies have provided mechanistic insights into the tail-to-tail dimerization coupling step as a suitable model for the propagation cycle of the HTP. The extensive energy profile was mapped out, and the experimentally observed unicity of the TPT-based catalysts was satisfactorily explained with the thermodynamic formation of key spirocyclic species.
Collapse
Affiliation(s)
- Miao Hong
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Xiaoyan Tang
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Laura Falivene
- King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, Kaust Catalysis Center, Thuwal 23955-6900, Saudi Arabia.,Dipartimento di Chimica e Biologia, Università di Salerno , Via Papa Paolo Giovanni II, I-84084, Fisciano, Italy
| | - Lucia Caporaso
- Dipartimento di Chimica e Biologia, Università di Salerno , Via Papa Paolo Giovanni II, I-84084, Fisciano, Italy
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, Kaust Catalysis Center, Thuwal 23955-6900, Saudi Arabia.,Dipartimento di Chimica e Biologia, Università di Salerno , Via Papa Paolo Giovanni II, I-84084, Fisciano, Italy
| | - Eugene Y-X Chen
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| |
Collapse
|
39
|
Nakano Y, Lupton DW. Enantioselective N‐Heterocyclic Carbene Catalysis by the Umpolung of α,β‐Unsaturated Ketones. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201510106] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
40
|
Nakano Y, Lupton DW. Enantioselective N‐Heterocyclic Carbene Catalysis by the Umpolung of α,β‐Unsaturated Ketones. Angew Chem Int Ed Engl 2016; 55:3135-9. [DOI: 10.1002/anie.201510106] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/24/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Yuji Nakano
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| | - David W. Lupton
- School of Chemistry Monash University Clayton 3800 Victoria Australia
| |
Collapse
|
41
|
Ghadwal RS. Carbon-based two electron σ-donor ligands beyond classical N-heterocyclic carbenes. Dalton Trans 2016; 45:16081-16095. [DOI: 10.1039/c6dt02158a] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Recent advances in N-heterocyclic carbene-derived carbon-based two electron σ-donor ligands are presented in this perspective.
Collapse
Affiliation(s)
- Rajendra S. Ghadwal
- Molecular Inorganic Chemistry and Catalysis
- Anorganische Chemie & Strukturchemie
- Fakultät für Chemie
- Universität Bielefeld
- Bielefeld
| |
Collapse
|
42
|
Rehbein J, Ruser SM, Phan J. NHC-catalysed benzoin condensation - is it all down to the Breslow intermediate? Chem Sci 2015; 6:6013-6018. [PMID: 29449915 PMCID: PMC5669215 DOI: 10.1039/c5sc02186c] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/20/2015] [Indexed: 11/21/2022] Open
Abstract
The Breslow catalytic cycle describing the benzoin condensation promoted by N-heterocyclic carbenes (NHC) as proposed in the late 1950s has since then been tried by generations of physical organic chemists. Emphasis has been laid on proofing the existence of an enaminol like structure (Breslow intermediate) that explains the observed umpolung of an otherwise electrophilic aldehyde. The present study is not focusing on spectroscopic elucidation of a thiazolydene based Breslow intermediate but rather tries to clarify if this key-intermediate is indeed directly linked with the product side of the overall reaction. The here presented EPR-spectroscopic and computational data provide a fundamentally different view on how the benzoin condensation may proceed: a radical pair could be identified as a second key-intermediate that is derived from the Breslow-intermediate via an SET process. These results highlight the close relationship to the Cannizarro reaction and oxidative transformations of aldehydes under NHC catalysis.
Collapse
Affiliation(s)
- Julia Rehbein
- Organische Chemie , Universität Hamburg , Martin-Luther-King-Platz 6 , Germany .
| | - Stephanie-M Ruser
- Organische Chemie , Universität Hamburg , Martin-Luther-King-Platz 6 , Germany .
| | - Jenny Phan
- Organische Chemie , Universität Hamburg , Martin-Luther-King-Platz 6 , Germany .
| |
Collapse
|
43
|
Flanigan DM, Romanov-Michailidis F, White NA, Rovis T. Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes. Chem Rev 2015; 115:9307-87. [PMID: 25992594 PMCID: PMC4986729 DOI: 10.1021/acs.chemrev.5b00060] [Citation(s) in RCA: 1418] [Impact Index Per Article: 157.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Darrin M Flanigan
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
| | | | - Nicholas A White
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
| |
Collapse
|
44
|
Tian Y, Lee JK. Gas Phase Studies of N-Heterocyclic Carbene-Catalyzed Condensation Reactions. J Org Chem 2015; 80:6831-8. [PMID: 26066314 DOI: 10.1021/acs.joc.5b01069] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N-Heterocyclic carbenes (NHCs) catalyze Umpolung condensation reactions of carbonyl compounds, including the Stetter reaction. These types of reactions have not heretofore been examined in the gas phase. Herein, we explore the feasibility of examining these reactions in the absence of solvent. A charge-tagged thiazolylidene catalyst is used to track the reactions by mass spectrometry. We find that the first Umpolung step, the addition of the NHC catalyst to a carbonyl compound to form the "Breslow intermediate", does not readily proceed in the gas phase, contrary to the case in solution. The use of acylsilanes in place of the carbonyl compounds appears to solve this issue, presumably because of a favorable Brook rearrangement. The second addition reaction, with enones, does not occur under our gas phase conditions. These reactions do occur in solution; the differential reactivity between the condensed and gas phases is discussed, and calculations are used to aid in the interpretation of the results.
Collapse
Affiliation(s)
- Yuan Tian
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, United States
| | - Jeehiun K Lee
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, United States
| |
Collapse
|
45
|
Zheng PC, Cheng J, Su S, Jin Z, Wang YH, Yang S, Jin LH, Song BA, Chi YR. Oxidative N-Heterocyclic Carbene-Catalyzed γ-Carbon Addition of Enals to Imines: Mechanistic Studies and Access to Antimicrobial Compounds. Chemistry 2015; 21:9984-7. [DOI: 10.1002/chem.201501632] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 11/10/2022]
|
46
|
Collett CJ, Massey RS, Taylor JE, Maguire OR, O'Donoghue AC, Smith AD. Rate and equilibrium constants for the addition of N-heterocyclic carbenes into benzaldehydes: a remarkable 2-substituent effect. Angew Chem Int Ed Engl 2015; 54:6887-92. [PMID: 25908493 PMCID: PMC4510784 DOI: 10.1002/anie.201501840] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Indexed: 11/23/2022]
Abstract
Rate and equilibrium constants for the reaction between N-aryl triazolium N-heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3-(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse reactions, plus onwards reaction to the Breslow intermediate, demonstrate the remarkable effect of the benzaldehyde 2-substituent in these reactions and provide insight into the chemoselectivity of cross-benzoin reactions.
Collapse
Affiliation(s)
- Christopher J Collett
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/
| | - Richard S Massey
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK)
| | - James E Taylor
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/
| | - Oliver R Maguire
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK)
| | | | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/.
| |
Collapse
|
47
|
Collett CJ, Massey RS, Taylor JE, Maguire OR, O'Donoghue AC, Smith AD. Rate and Equilibrium Constants for the Addition of N-Heterocyclic Carbenes into Benzaldehydes: A Remarkable 2-Substituent Effect. ACTA ACUST UNITED AC 2015; 127:6991-6996. [PMID: 27478264 PMCID: PMC4955233 DOI: 10.1002/ange.201501840] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Indexed: 12/01/2022]
Abstract
Rate and equilibrium constants for the reaction between N‐aryl triazolium N‐heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3‐(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse reactions, plus onwards reaction to the Breslow intermediate, demonstrate the remarkable effect of the benzaldehyde 2‐substituent in these reactions and provide insight into the chemoselectivity of cross‐benzoin reactions.
Collapse
Affiliation(s)
- Christopher J. Collett
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch‐www.st‐andrews.ac.uk/staff/ads/group/
| | - Richard S. Massey
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK)
| | - James E. Taylor
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch‐www.st‐andrews.ac.uk/staff/ads/group/
| | - Oliver R. Maguire
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK)
| | | | - Andrew D. Smith
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch‐www.st‐andrews.ac.uk/staff/ads/group/
| |
Collapse
|
48
|
Kelemen Z, Streubel R, Nyulászi L. Zwitterionic carbene adducts and their carbene isomers. RSC Adv 2015. [DOI: 10.1039/c5ra07039b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
N-heterocyclic carbenes (NHC) and abnormal NHCs (aNHC) form the stable adducts,1and2, with X (CH2, SiH2, NH, PH, O, S), which are excellent nucleophiles at X.
Collapse
Affiliation(s)
- Z. Kelemen
- Department of Inorganic and Analytical Chemistry
- Budapest University of Technology and Economics
- Budapest
- Hungary
| | - R. Streubel
- Institut fur Anorganische Chemie der
- Rheinischen Friedrich-Wilhelms-Universitat Bonn
- 53121 Bonn
- Germany
| | - L. Nyulászi
- Department of Inorganic and Analytical Chemistry
- Budapest University of Technology and Economics
- Budapest
- Hungary
| |
Collapse
|
49
|
Ghadwal RS, Schürmann CJ, Andrada DM, Frenking G. Mono- and di-cationic hydrido boron compounds. Dalton Trans 2015. [DOI: 10.1039/c5dt02237a] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Stable mono- and di-cationic hydrido boron compounds featuring CH2BH2(μ-H)BH2CH2 and CH2BH(μ-H)2BHCH2 cores are readily accessible by dehydrogenative hydride abstractions. NBO calculations revealed the occurrence of two B–H–B 3c–2e bonds in the HB(μ-H)2BH moiety of di-cations (7 and 8), where 43% is located at the H bridges and ∼28% at each boron atom.
Collapse
Affiliation(s)
- Rajendra S. Ghadwal
- Institut für Anorganische Chemie
- Universität Bielefeld
- 33615 Bielefeld
- Germany
- Institut für Anorganische Chemie der Georg-August-Universität Göttingen
| | - Christian J. Schürmann
- Institut für Anorganische Chemie der Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
| | - Diego M. Andrada
- Fachbereich Chemie
- Philipps-Universität Marburg
- 35032 Marburg
- Germany
| | - Gernot Frenking
- Fachbereich Chemie
- Philipps-Universität Marburg
- 35032 Marburg
- Germany
| |
Collapse
|
50
|
Gualandi A, Mengozzi L, Manoni E, Cozzi PG. Stereoselective Organocatalytic Addition of Nucleophiles to Isoquinolinium and 3,4-dihydroisoquinolinium Ions: A Simple Approach for the Synthesis of Isoquinoline Alkaloids. Catal Letters 2014. [DOI: 10.1007/s10562-014-1396-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|