1
|
Baroudi A, Jaradat K, Karton A. 6-Endo-dig versus 5-exo-dig: Exploring Radical Cyclization Preference with First-, Second-, and Third-row Linkers using High-level Quantum Chemical Methods. Chemphyschem 2023; 24:e202300426. [PMID: 37392178 DOI: 10.1002/cphc.202300426] [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: 06/20/2023] [Revised: 06/25/2023] [Accepted: 06/26/2023] [Indexed: 07/03/2023]
Abstract
As an expansion upon Baldwin rules, the cyclization reactions of hex-5-yn-1-yl radical systems with different first-, second-, and third-row linkers are explored at the CCSD(T) level via means of the SMD(benzene)-G4(MP2) thermochemical protocol. Unlike C, O, and N linkers, systems with B, Si, P, S, Ge, As, and Se linkers are shown to favor 6-endo-dig cyclization. This offers fundamental insights into the rational synthetic design of cyclic compounds. A thorough analysis of stereoelectronic effects, cyclization barriers, and intrinsic barriers illustrates that structural changes alter the cyclization preference by mainly impacting 5-exo-dig reaction barriers. Based on the high-level computational modeling, we proceed to develop a new tool for cyclization preference prediction from the correlation between cyclization barriers and radical structural parameters (e. g., linker bond length and bond angle). A strong correlation is found between the radical attack trajectory angle and the reaction barrier heights, i. e., cyclization preference. Finally, the influence of stereoelectronic effects on the two radical cyclization pathways is further investigated in stereoisomers of hypervalent silicon system, which provides novel insight into cyclization control.
Collapse
Affiliation(s)
- Abdulkader Baroudi
- College of Engineering and Technology, American University of the Middle East, Kuwait
| | - Khaled Jaradat
- College of Engineering and Technology, American University of the Middle East, Kuwait
| | - Amir Karton
- School of Science and Technology, University of New England, Armidale, NSW 2351, Australia
| |
Collapse
|
2
|
Sadanandan S, Gupta DK. Changing stereoselectivity and regioselectivity in copper( i)-catalyzed 5- exo cyclization by chelation and rigidity in aminoalkyl radicals: synthesis towards diverse bioactive N-heterocycles. NEW J CHEM 2020. [DOI: 10.1039/c9nj05166j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Chelation, rigidity and carbon-radical positions in aminoalkyl precursors disturb the usual 2,4-trans diastereoselectivity and 5-exo mode in Cu(i)-catalyzed ATRC.
Collapse
|
3
|
Chatgilialoglu C, Ferreri C, Landais Y, Timokhin VI. Thirty Years of (TMS)3SiH: A Milestone in Radical-Based Synthetic Chemistry. Chem Rev 2018; 118:6516-6572. [DOI: 10.1021/acs.chemrev.8b00109] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | - Carla Ferreri
- ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy
| | - Yannick Landais
- University of Bordeaux, Institute of Molecular Sciences, UMR-CNRS 5255, 351 cours de la libération, 33405 Talence Cedex, France
| | - Vitaliy I. Timokhin
- Department of Biochemistry, University of Wisconsin-Madison, 1552 University Avenue, Madison, Wisconsin 53726, United States
| |
Collapse
|
4
|
Zhong X, Chen N, Xu J. A concise synthesis of cyclobrassinin and its analogues via a thiyl radical aromatic substitution. NEW J CHEM 2018. [DOI: 10.1039/c8nj02037j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Cyclobrassinin and its six and seven-membered ring analogues have been synthesized through a thiyl radical-mediated intramolecular aromatic substitution of brassinin derivatives.
Collapse
Affiliation(s)
- Xin Zhong
- State Key Laboratory of Chemical Resource Engineering
- Department of Organic Chemistry
- Faculty of Science
- Beijing University of Chemical Technology
- Beijing 100029
| | - Ning Chen
- State Key Laboratory of Chemical Resource Engineering
- Department of Organic Chemistry
- Faculty of Science
- Beijing University of Chemical Technology
- Beijing 100029
| | - Jiaxi Xu
- State Key Laboratory of Chemical Resource Engineering
- Department of Organic Chemistry
- Faculty of Science
- Beijing University of Chemical Technology
- Beijing 100029
| |
Collapse
|
5
|
Jäger CM, Croft AK. Radical Reaction Control in the AdoMet Radical Enzyme CDG Synthase (QueE): Consolidate, Destabilize, Accelerate. Chemistry 2017; 23:953-962. [PMID: 27859789 PMCID: PMC5347944 DOI: 10.1002/chem.201604719] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Indexed: 12/29/2022]
Abstract
Controlling radical intermediates and thus catalysing and directing complex radical reactions is a central feature of S-adensosylmethionine (SAM)-dependent radical enzymes. We report ab initio and DFT calculations highlighting the specific influence of ion complexation, including Mg2+ , identified as a key catalytic component on radical stability and reaction control in 7-carboxy-7-deazaguanine synthase (QueE). Radical stabilisation energies (RSEs) of key intermediates and radical clock-like model systems of the enzyme-catalysed rearrangement of 6-carboxytetrahydropterin (CPH4), reveals a directing role of Mg2+ in destabilising both the substrate-derived radical and corresponding side reactions, with the effect that the experimentally-observed rearrangement becomes dominant over possible alternatives. Importantly, this is achieved with minimal disruption of the thermodynamics of the substrate itself, affording a novel mechanism for an enzyme to both maintain binding potential and accelerate the rearrangement step. Other mono and divalent ions were probed with only dicationic species achieving the necessary radical conformation to facilitate the reaction.
Collapse
Affiliation(s)
- Christof M. Jäger
- The University of NottinghamDepartment of Chemical and Environmental EngineeringUniversity ParkNottinghamNG7 2RDUnited Kingdom
| | - Anna K. Croft
- The University of NottinghamDepartment of Chemical and Environmental EngineeringUniversity ParkNottinghamNG7 2RDUnited Kingdom
| |
Collapse
|
6
|
Walton JC. The importance of chain conformational mobility during 5-exo-cyclizations of C-, N- and O-centred radicals. Org Biomol Chem 2015; 12:7983-92. [PMID: 25179567 DOI: 10.1039/c4ob01419g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction coordinates of an archetypical set of 5-exo cyclizations of C-, N- and O-centred radicals were investigated by computational methods. G4 theory, and DFT with the um062x functional, were able to rationalise counterintuitive factors such as the 'normal' order of rate constants being: N-centred < C-centred < O-centred radicals. The access angle between the radical centre and the double bond was identified as a key factor. Examination of its evolution during ring closure implied that rigidity at the N-ends of the chains, and the consequent extra energy needed to attain chair-like transition states, might be the reason for slow aminyl cyclizations. A novel linear correlation between cyclization activation energies and the access angles was discovered. The preference for cis-1,2-disubstituted product formation was also accounted for in terms of interaction between the hyperconjugatively delocalized SOMO and the alkene π* orbital.
Collapse
Affiliation(s)
- John C Walton
- University of St. Andrews, EaStCHEM School of Chemistry, St. Andrews, Fife, KY16 9ST, UK.
| |
Collapse
|
7
|
Sumino S, Fusano A, Fukuyama T, Ryu I. Carbonylation reactions of alkyl iodides through the interplay of carbon radicals and Pd catalysts. Acc Chem Res 2014; 47:1563-74. [PMID: 24712759 DOI: 10.1021/ar500035q] [Citation(s) in RCA: 346] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Numerous methods for transition metal catalyzed carbonylation reactions have been established. Examples that start from aryl, vinyl, allyl, and benzyl halides to give the corresponding carboxylic acid derivatives have all been well documented. In contrast, the corresponding alkyl halides often encounter difficulty. This is inherent to the relatively slow oxidative addition step onto the metal center and subsequent β-hydride elimination which causes isomerization of the alkyl metal species. Radical carbonylation reactions can override such problems of reactivity; however, carbonylation coupled to iodine atom transfer (atom transfer carbonylation), though useful, often suffers from a slow iodine atom transfer step that affects the outcome of the reaction. We found that atom transfer carbonylation of primary, secondary, and tertiary alkyl iodides was efficiently accelerated by the addition of a palladium catalyst under light irradiation. Stereochemical studies support a mechanistic pathway based on the synergic interplay of radical and Pd-catalyzed reaction steps which ultimately lead to an acylpalladium species. The radical/Pd-combined reaction system has a wide range of applications, including the synthesis of carboxylic acid esters, lactones, amides, lactams, and unsymmetrical ketones such as alkyl alkynyl and alkyl aryl ketones. The design of unique multicomponent carbonylation reactions involving vicinal C-functionalization of alkenes, double and triple carbonylation reactions, in tandem with radical cyclization reactions, has also been achieved. Thus, the radical/Pd-combined strategy provides a solution to a longstanding problem of reactivity involving the carbonylation of alkyl halides. This novel methodology expands the breadth and utility of carbonylation chemistry over either the original radical carbonylation reactions or metal-catalyzed carbonylation reactions.
Collapse
Affiliation(s)
- Shuhei Sumino
- Department
of Chemistry,
Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | - Akira Fusano
- Department
of Chemistry,
Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | - Takahide Fukuyama
- Department
of Chemistry,
Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | - Ilhyong Ryu
- Department
of Chemistry,
Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| |
Collapse
|
8
|
Abstract
Kinetic data for intramolecular homolytic substitution reactions of a series of acyl and oxyacyl radicals are reported.
Collapse
Affiliation(s)
- Amber N. Hancock
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology
- Australia
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute
- The University of Melbourne
- , Australia
| | - Carl H. Schiesser
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology
- Australia
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute
- The University of Melbourne
- , Australia
| |
Collapse
|
9
|
Hasegawa E, Tateyama M, Nagumo R, Tayama E, Iwamoto H. Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways. Beilstein J Org Chem 2013; 9:1397-406. [PMID: 23946834 PMCID: PMC3740709 DOI: 10.3762/bjoc.9.156] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/19/2013] [Indexed: 11/23/2022] Open
Abstract
Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives were investigated. The regioselectivities of these processes were found to be influenced by the structure of cyclopropanols as well as the counter anion of the copper(II) salts. A mechanism involving rearrangement reactions of radical intermediates and their competitive trapping by copper ions is proposed.
Collapse
Affiliation(s)
- Eietsu Hasegawa
- Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan
| | | | | | | | | |
Collapse
|
10
|
Hancock AN, Schiesser CH. Guidelines for radical reactions: some thirty years on. Chem Commun (Camb) 2013; 49:9892-5. [DOI: 10.1039/c3cc43870h] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
11
|
Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with amines: selective reaction pathways depending on the nature of the amine radical cations. RESEARCH ON CHEMICAL INTERMEDIATES 2012. [DOI: 10.1007/s11164-012-0646-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
12
|
Jäger C, Hennemann M, Clark T. The Effect of a Complexed Lithium Cation on a Norcarane-Based Radical Clock. Chemistry 2009; 15:2425-33. [DOI: 10.1002/chem.200801076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
13
|
Tsuchida H, Tamura M, Hasegawa E. Cyclization and Ring-Expansion Processes Involving Samarium Diiodide Promoted Reductive Formation and Subsequent Oxidative Ring Opening of Cyclopropanol Derivatives. J Org Chem 2009; 74:2467-75. [DOI: 10.1021/jo802749g] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hiroyuki Tsuchida
- Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan
| | - Mutsuko Tamura
- Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan
| | - Eietsu Hasegawa
- Department of Chemistry, Faculty of Science, Niigata University, Ikarashi-2 8050, Niigata 950-2181, Japan
| |
Collapse
|
14
|
Bennasar ML, Roca T, García-Díaz D. A New Acyl Radical-based Route to the 1,5-Methanoazocino[4,3-b]indole Framework of Uleine and Strychnos Alkaloids. J Org Chem 2008; 73:9033-9. [DOI: 10.1021/jo801998h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M.-Lluïsa Bennasar
- Laboratory of Organic Chemistry, Faculty of Pharmacy, and Institut de Biomedicina (IBUB), University of Barcelona, Barcelona 08028, Spain
| | - Tomàs Roca
- Laboratory of Organic Chemistry, Faculty of Pharmacy, and Institut de Biomedicina (IBUB), University of Barcelona, Barcelona 08028, Spain
| | - Davinia García-Díaz
- Laboratory of Organic Chemistry, Faculty of Pharmacy, and Institut de Biomedicina (IBUB), University of Barcelona, Barcelona 08028, Spain
| |
Collapse
|
15
|
Beaume A, Courillon C, Derat E, Malacria M. Unprecedented Aromatic Homolytic Substitutions and Cyclization of AmideIminyl Radicals: Experimental and Theoretical Study. Chemistry 2008; 14:1238-52. [DOI: 10.1002/chem.200700884] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
16
|
Schiesser CH, Wille U, Matsubara H, Ryu I. Radicals masquerading as electrophiles: dual orbital effects in nitrogen-philic acyl radical cyclization and related addition reactions. Acc Chem Res 2007; 40:303-13. [PMID: 17444607 DOI: 10.1021/ar600015v] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Free-radical chemistry has come a long way in a relatively short period of time. The synthetic practitioner takes for granted the wealth of mechanistic and rate constant data now available and can apply free-radical techniques to the synthesis of many different classes of target molecule with confidence. Despite this, there are still mechanistic anomalies that need to be addressed. This Account highlights recent work involving nucleophilic radicals with low-lying unoccupied orbitals, such as acyl, oxyacyl, silyl, stannyl, and germyl radicals. Through interesting singly occupied molecular orbital (SOMO)-pi* and highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) interactions during these reactions, the radicals involved are able to mask as electrophiles, providing high levels of regiocontrol and efficient methods for the synthesis of important heterocycles.
Collapse
Affiliation(s)
- Carl H Schiesser
- School of Chemistry, The University of Melbourne, Victoria, Australia
| | | | | | | |
Collapse
|
17
|
Synthesis of trans-perhydroisoquinolines by 6-endo-trig radical cyclization of amino-tethered vinyl bromides and cyclohexenes. Tetrahedron 2007. [DOI: 10.1016/j.tet.2006.11.087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
18
|
|
19
|
Servais A, Azzouz M, Lopes D, Courillon C, Malacria M. Radical Cyclization ofN-Acylcyanamides: Total Synthesis of Luotonin A. Angew Chem Int Ed Engl 2007; 46:576-9. [PMID: 17154202 DOI: 10.1002/anie.200602940] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Aurore Servais
- Laboratoire de Chimie Organique, UMR CNRS 7611, Institut de Chimie Moléculaire, FR 2769, Université Pierre et Marie Curie, Paris 6, case 229, 4 place Jussieu, 75252 Paris, France
| | | | | | | | | |
Collapse
|
20
|
Matsubara H, Falzon CT, Ryu I, Schiesser CH. Radicals masquerading as electrophiles: a computational study of the intramolecular addition reactions of acyl radicals to imines. Org Biomol Chem 2006; 4:1920-6. [PMID: 16688338 DOI: 10.1039/b603024f] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ab initio calculations using 6-311G**, cc-pVDZ, and aug-cc-pVDZ, with (MP2, QCISD, CCSD(T)) and without (UHF) electron correlation, and density functional methods (BHandHLYP and B3LYP) predict that cyclization of the 5-aza-5-hexenoyl and (E)-6-aza-5-hexenoyl radicals proceed to afford the 5-exo products. At the CCSD(T)/cc-pVDZ//BHandHLYP/cc-pVDZ level of theory, energy barriers (deltaE(double dagger)) of 36.1 and 47.0 kJ mol(-1) were calculated for the 5-exo and 6-endo pathways for the cyclization of the 5-aza-5-hexenoyl radical. On the other hand, at the same level of theory, deltaE(double dagger) of 38.9 and 45.4 kJ mol(-1) were obtained for the 5-exo and 6-endo cyclization modes of (E)-6-aza-5-hexenoyl radical, with exothermicities of about 27 and 110 kJ mol(-1) calculated for the exo and endo modes, respectively. Under suitable experimental conditions, the 6-endo cyclization product is likely to dominate. Analysis of the molecular orbitals involved in these ring-closure reactions indicate that both reactions at nitrogen are assisted by dual orbital interactions involving simultaneous SOMO-pi* and LP-pi* overlap in the transitions states. Interestingly, the (Z)-6-aza-5-hexenoyl radical, that cannot benefit from these dual orbital effects is predicted to ring-close exclusively in the 5-exo fashion.
Collapse
Affiliation(s)
- Hiroshi Matsubara
- Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
| | | | | | | |
Collapse
|
21
|
Hasegawa E, Tsuchida H, Tamura M. Cyclization and Ring-expansion Reactions Involving Reductive Formation and Oxidative Ring-opening of Cyclopropanol Derivatives. CHEM LETT 2005. [DOI: 10.1246/cl.2005.1688] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
22
|
Synthesis of Se-arylmethyl selenoformates by reaction of aluminum arylmethaneselenolates with formates. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.01.148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
23
|
Majumdar KC, Basu PK, Mukhopadhyay PP. Formation of five- and six-membered heterocyclic rings under radical cyclisation conditions. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.05.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
24
|
Lee D, Otte RD. Transition-Metal-Catalyzed Aldehydic C−H Activation by Azodicarboxylates. J Org Chem 2004; 69:3569-71. [PMID: 15132574 DOI: 10.1021/jo035456o] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rhodium acetate-catalyzed hydroacylation between aldehydes and an activated form of N=N bond was achieved under mild conditions to provide efficient access to a variety of hydrazino imides. Good selectivity for the aldehydic C-H activation relative to the ene-type reaction was observed with aldehydes having unsaturation both at terminal and internal positions.
Collapse
Affiliation(s)
- Daesung Lee
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
| | | |
Collapse
|
25
|
Minozzi M, Nanni D, Walton JC. Alkanethioimidoyl Radicals: Evaluation of β-Scission Rates and of Cyclization onto S-Alkenyl Substituents. J Org Chem 2004; 69:2056-69. [PMID: 15058954 DOI: 10.1021/jo0353637] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thioimidoyl radicals were generated by addition of alkylsulfanyl radicals to alkyl isonitriles and were characterized by electron paramagnetic resonance (EPR) spectroscopy. The beta-scissions of their C.S-C bonds were studied by variable-temperature EPR spectroscopy and the fragmentation rate constants and activation energies were calculated. The scission rates depend on the stability of the released alkyl radicals but in any case, at room temperature, the processes were fast. Data collected on similar oxyimidoyls showed that their fragmentations are slightly slower compared to those of analogous thioimidoyls. The scission rates of selenoimidoyls could not be studied by EPR and were evaluated by theoretical calculations. EPR experiments also enabled both beta-scission and 5-exo ring closure rate constants of two S-but-3-enyl-substituted imidoyl radicals to be determined, showing that cyclization prevails only at low temperatures. Density functional theory (DFT) theoretical calculations predicted that the fragmentation process preferentially occurs from the s-cis rotamers (X-C bond) of the imidoyl radicals. Thio- and seleno-imidoyls (but not oxyimidoyls) prefer s-trans conformations so that their fragmentations involve prior rotation about the X-C bond.
Collapse
Affiliation(s)
- Matteo Minozzi
- School of Chemistry, University of St. Andrews, Fife KY16 9ST, Scotland, United Kingdom
| | | | | |
Collapse
|
26
|
Highly efficient carbonylation reactions of organic halides in supercritical carbon dioxide. PROGRESS IN NUCLEAR ENERGY 2000. [DOI: 10.1016/s0149-1970(00)00083-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
27
|
Dang HS, Roberts BP. Radical-chain cyclisation of unsaturated acetals and thioacetals in the presence of thiols as polarity-reversal catalysts. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(99)01898-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
28
|
|
29
|
Ryu I, Ogura SI, Minakata S, Komatsu M. Vinyl radical cyclization onto imino group. Selective 6-endo cyclization onto aldimines leading to 3-methylenepiperidines. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(98)02666-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
30
|
Chatgilialoglu C, Newcomb M. Hydrogen Donor Abilities of the Group 14 Hydrides. ADVANCES IN ORGANOMETALLIC CHEMISTRY 1999. [DOI: 10.1016/s0065-3055(08)60620-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
31
|
Rigby JH, Danca DM, Horner JH. Carbamoyl radicals from Se-phenylselenocarbamates: Intramolecular additions to alkenes. Tetrahedron Lett 1998. [DOI: 10.1016/s0040-4039(98)01830-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
32
|
First example of samarium diiodide-promoted sequential cyclization and ring-expansion reactions of α-bromomethyl cyclic β-keto esters to homologated γ-keto esters. Tetrahedron Lett 1998. [DOI: 10.1016/s0040-4039(98)00658-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
33
|
Beckwith ALJ, Crich D, Duggan PJ, Yao Q. Chemistry of beta-(Acyloxy)alkyl and beta-(Phosphatoxy)alkyl Radicals and Related Species: Radical and Radical Ionic Migrations and Fragmentations of Carbonminus signOxygen Bonds. Chem Rev 1997; 97:3273-3312. [PMID: 11851491 DOI: 10.1021/cr950207o] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Athelstan L. J. Beckwith
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia, Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, and Department of Chemistry, Monash University, Clayton, Victoria 3168, Australia
| | | | | | | |
Collapse
|