1
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Ji K, Parthiban J, Jockusch S, Sivaguru J, Porco JA. Triple-Dearomative Photocycloaddition: A Strategy to Construct Caged Molecular Frameworks. J Am Chem Soc 2024; 146:13445-13454. [PMID: 38708818 PMCID: PMC11149169 DOI: 10.1021/jacs.4c02674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
An unprecedented caged 2H-benzo-dioxo-pentacycloundecane framework was serendipitously obtained in a single transformation via triple-dearomative photocycloaddition of chromone esters with furans. This caged structure was generated as part of an effort to access a tricyclic, oxygen-bridged intermediate enroute to the dihydroxanthone natural product nidulalin A. Reaction scope and limitations were thoroughly investigated, revealing the ability to access a multitude of synthetically challenging caged scaffolds in a two-step sequence. Photophysical studies provided key mechanistic insights on the process for formation of the novel caged scaffold.
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Affiliation(s)
- Kaijie Ji
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, Massachusetts, 02215, United States
| | - Jayachandran Parthiban
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio, 43403, United States
| | - Steffen Jockusch
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio, 43403, United States
| | - Jayaraman Sivaguru
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio, 43403, United States
| | - John A. Porco
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, Massachusetts, 02215, United States
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2
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Kong L, Yu H, Deng M, Wu F, Chen SC, Luo T. Enantioselective Total Syntheses of Grayanane Diterpenoids and (+)-Kalmanol: Evolution of the Bridgehead Carbocation-Based Cyclization and Late-Stage Functional Group Manipulation Strategies. J Org Chem 2023; 88:6017-6038. [PMID: 37094797 DOI: 10.1021/acs.joc.3c00365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
Abstract
Grayanane diterpenoids contain over 300 highly oxidized and structurally complex members, many of which possess important biological activities. Full details are provided for the development of the concise, enantioselective and divergent total syntheses of grayanane diterpenoids and (+)-kalmanol. The unique 7-endo-trig cyclization based on a bridgehead carbocation was designed and implemented to construct the 5/7/6/5 tetracyclic skeleton, demonstrating the practical value of the bridgehead carbocation-based cyclization strategy. Extensive studies of late-stage functional group manipulation were performed to forge the C1 stereogenic center, during which a photoexcited intramolecular hydrogen atom transfer reaction was discovered and the mechanism was further studied through density functional theory (DFT) calculations. The biomimetic 1,2-rearrangement from the grayanoid skeleton provided a 5/8/5/5 tetracyclic framework and resulted in the first total synthesis of (+)-kalmanol.
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Affiliation(s)
- Lingran Kong
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Hang Yu
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Mengping Deng
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Fanrui Wu
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Si-Cong Chen
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Tuoping Luo
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
- Institute of Molecular Physiology, Shenzhen Bay Laboratory, Shenzhen, Guangdong 518055, China
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3
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Jones B, Solon P, Popescu MV, Du JY, Paton R, Smith MD. Catalytic Enantioselective 6π Photocyclization of Acrylanilides. J Am Chem Soc 2022; 145:171-178. [PMID: 36571763 PMCID: PMC9837842 DOI: 10.1021/jacs.2c09267] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Controlling absolute stereochemistry in catalytic photochemical reactions is generally challenging owing to high rates of background reactivity. Successful strategies broadly rely on selective excitation of the reaction substrate when associated with a chiral catalyst. Recent studies have demonstrated that chiral Lewis acid complexes can enable selective energy transfer from a photosensitizer to facilitate enantioselective triplet state reactions. Here, we apply this approach to the enantioselective catalysis of a 6π photocyclization through the design of an iridium photosensitizer optimized to undergo energy transfer to a reaction substrate only in the presence of a chiral Lewis acid complex. Among a group of iridium(III) sensitizers, enantioselectivity and yield closely correlate with photocatalyst triplet energy within a narrow window enabled by a modest reduction in substrate triplet energy upon binding a scandium/ligand complex. These results demonstrate that photocatalyst tuning offers a means to suppress background reactivity and improve enantioselectivity in photochemical reactions.
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Affiliation(s)
- Benjamin
A. Jones
- Chemistry
Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Pearse Solon
- Chemistry
Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Mihai V. Popescu
- Chemistry
Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.,Department
of Chemistry, Colorado State University, 1301 Center Avenue, Ft. Collins, Colorado 80523-1872, United States
| | - Ji-Yuan Du
- Chemistry
Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Robert Paton
- Department
of Chemistry, Colorado State University, 1301 Center Avenue, Ft. Collins, Colorado 80523-1872, United States,
| | - Martin D. Smith
- Chemistry
Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.,
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4
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Oddy MJ, Kusza DA, Epton RG, Lynam JM, Unsworth WP, Petersen WF. Visible-Light-Mediated Energy Transfer Enables the Synthesis of β-Lactams via Intramolecular Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2022; 61:e202213086. [PMID: 36205440 PMCID: PMC9828223 DOI: 10.1002/anie.202213086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Indexed: 11/07/2022]
Abstract
The synthesis of 2-azetidinones (β-lactams) from simple acrylamide starting materials by visible-light-mediated energy transfer catalysis is reported. The reaction features a C(sp3 )-H functionalization via a variation of the Norrish-Yang photocyclization involving a carbon-to-carbon 1,5-hydrogen atom transfer (supported by deuterium labelling and DFT calculations) and can be used for the construction of a diverse range of β-lactam products.
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Affiliation(s)
- Meghan J. Oddy
- Department of ChemistryUniversity of Cape TownRondebosch, Cape Town7700South Africa
| | - Daniel A. Kusza
- Department of ChemistryUniversity of Cape TownRondebosch, Cape Town7700South Africa
| | - Ryan G. Epton
- Department of ChemistryUniversity of YorkYorkYO10 5DDUK
| | | | | | - Wade F. Petersen
- Department of ChemistryUniversity of Cape TownRondebosch, Cape Town7700South Africa
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5
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Liu J, Hao T, Qian L, Shi M, Wei Y. Construction of Benzocyclobutenes Enabled by Visible‐Light‐Induced Triplet Biradical Atom Transfer of Olefins. Angew Chem Int Ed Engl 2022; 61:e202204515. [DOI: 10.1002/anie.202204515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Indexed: 11/12/2022]
Affiliation(s)
- Jiaxin Liu
- State Key Laboratory of Organometallic Chemistry University of Chinese Academy of Sciences Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
- CAS Key Laboratory of Energy Regulation Materials Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
| | - Tonggang Hao
- State Key Laboratory of Organometallic Chemistry University of Chinese Academy of Sciences Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
| | - Ling Qian
- Key Laboratory for Advanced Materials & Institute of Fine Chemicals Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center School of Chemistry & Molecular Engineering East China University of Science and Technology 130 Meilong Road Shanghai 200237 China
| | - Min Shi
- State Key Laboratory of Organometallic Chemistry University of Chinese Academy of Sciences Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
- Key Laboratory for Advanced Materials & Institute of Fine Chemicals Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center School of Chemistry & Molecular Engineering East China University of Science and Technology 130 Meilong Road Shanghai 200237 China
| | - Yin Wei
- State Key Laboratory of Organometallic Chemistry University of Chinese Academy of Sciences Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
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6
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Liu J, Hao T, Qian L, Shi M, Wei Y. Construction of Benzocyclobutenes Enabled by Visible‐Light‐Induced Triplet Biradical Atom Transfer of Olefins. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jiaxin Liu
- Shanghai Institute of Organic Chemistry State Key Laboratory of Organometallic Chemistry Shanghai CHINA
| | - Tonggang Hao
- Shanghai Institute of Organic Chemistry State Key Laboratory of Organometallic Chemistry Shanghai CHINA
| | - Ling Qian
- East China University of Science and Technology School of Chemistry & Molecular Engineering Shanghai CHINA
| | - Min Shi
- Shanghai Institute of Organic Chemistry State Key Laboratory of Organometallic Chemistry Shanghai CHINA
| | - Yin Wei
- Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences State Key Laboratory of Organometallic Chemistry 345 Lingling Road 200032 Shanghai CHINA
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7
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Xiong Y, Großkopf J, Jandl C, Bach T. Visible Light-Mediated Dearomative Hydrogen Atom Abstraction/ Cyclization Cascade of Indoles. Angew Chem Int Ed Engl 2022; 61:e202200555. [PMID: 35213774 PMCID: PMC9314014 DOI: 10.1002/anie.202200555] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Indexed: 11/24/2022]
Abstract
The photochemical synthesis of yet unknown 2‐oxospiro[azetidine‐3,3′‐indolines] (17 examples, 80–95 % yield), 2,4‐dioxospiro[azetidine‐3,3′‐indolines] (eight examples, 87–97 % yield), and 1‐oxo‐1,3‐dihydrospiro[indene‐2,3′‐indolines] (17 examples, 85–97 % yield) is described. Starting from readily accessible 3‐substituted indoles, a dearomatization of the indole core was accomplished upon irradiation at λ=420 nm in the presence of thioxanthen‐9‐one (10 mol%) as the sensitizer. Based on mechanistic evidence (triplet energy determination, deuteration experiments, by‐product analysis) it is proposed that the reaction proceeds by energy transfer via a 1,4‐ or 1,5‐diradical intermediate. The latter intermediates are formed by excited state hydrogen atom transfer from suitable alkyl groups within the C3 substituent to the indole C2 carbon atom. Subsequent ring closure proceeds with pronounced diastereoselectivity to generate a 4‐ or 5‐membered spirocyclic dearomatized product with several options for further functionalization.
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Affiliation(s)
- Yang Xiong
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, 85747, Garching, Germany
| | - Johannes Großkopf
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, 85747, Garching, Germany
| | - Christian Jandl
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, 85747, Garching, Germany
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC), School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, 85747, Garching, Germany
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8
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Kandappa SK, Ahuja S, Singathi R, Valloli LK, Baburaj S, Parthiban J, Sivaguru J. Using Restricted Bond Rotations to Enforce Excited State Behavior of Organic Molecules. Synlett 2022. [DOI: 10.1055/a-1785-6910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This account highlights the role of restricted bond rotations to influence excited state reactivity of organic molecules. It highlights photochemical reactivity of various organic molecules and the design strategies that could be exploited by chemists to utilize restricted bond rotations to uncover new excited state reactivity and achieve selectivity.
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Affiliation(s)
- Sunil Kumar Kandappa
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Sapna Ahuja
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Ravichandranath Singathi
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Lakshmy Kannadi Valloli
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Sruthy Baburaj
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Jayachandran Parthiban
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Jayaraman Sivaguru
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
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9
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Xiong Y, Großkopf J, Jandl C, Bach T. Visible Light‐Mediated Dearomative Hydrogen Atom Abstraction/ Cyclization Cascade of Indoles. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202200555] [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)
- Yang Xiong
- Technische Universität München: Technische Universitat Munchen Chemistry GERMANY
| | - Johannes Großkopf
- Technische Universität München: Technische Universitat Munchen Chemistry GERMANY
| | - Christian Jandl
- Technische Universität München: Technische Universitat Munchen Chemistry GERMANY
| | - Thorsten Bach
- Technische Universität München Lehrstuhl für Organische Chemie I Lichtenbergstr. 4 85747 Garching GERMANY
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10
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Alves NG, Alves AJS, Soares MIL, Pinho e Melo TMVD. Recent Advances in the Synthesis of Spiro‐β‐Lactams and Spiro‐δ‐Lactams. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100013] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Nuno G. Alves
- University of Coimbra Coimbra Chemistry Centre and Department of Chemistry 3004-535 Coimbra Portugal
| | - Américo J. S. Alves
- University of Coimbra Coimbra Chemistry Centre and Department of Chemistry 3004-535 Coimbra Portugal
| | - Maria I. L. Soares
- University of Coimbra Coimbra Chemistry Centre and Department of Chemistry 3004-535 Coimbra Portugal
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11
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Liu H, Gao H, Wang S, Yao S, Wu F, Zhao Y, Chan KS, Shen Z. Regulation of an Ambient-Light-Induced Photocyclization Pathway (Norrish-Yang Versus 6π) by Substituent Choice. Chemistry 2020; 26:12418-12430. [PMID: 32372418 DOI: 10.1002/chem.202000990] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/28/2020] [Indexed: 12/12/2022]
Abstract
Photocyclization, irrespective of whether multiple steps (e.g., Norrish-Yang cyclization) or a single concerted step (e.g., 6π photocyclization) are involved, is an intramolecular photochemical process resulting in the formation of one new single bond to afford a ring system. In particular, visible-light-induced photocyclization offers a green and sustainable route to organic cyclic compounds that are difficult to access by thermal reactions. Herein, we describe the ambient light-induced intramolecular photocyclization of a series of donor/acceptor chromophores 1 d-3 d containing two types of photoresponsive motifs, namely an electron-deficient BF2 -chelated ketone fused with an electron-rich thiophene, and probe the solution-phase and solid-state photochromic performance of these compounds. The results reveal that simple variation of R substituents on the diaryl moiety allows one to control the intramolecular photocyclization mechanism with high photochemical selectivity, e.g., under ambient light, methyl-substituted 1 d and 2 d undergo reversible 6π photocyclization, whereas ethyl-substituted 3 d exclusively undergoes irreversible Norrish-Yang photocyclization. Single-crystal X-ray analysis of Norrish-Yang cyclization products reveals the formation of four pairs of conformational enantiomers differing in the dihedral angle between benzothiophene and the BF2 core, namely (±)N-3 d@68°, (±)N-3 d@-77°, (±)N-3 d@-78°, and (±)N-3 d@-102°. The UV/Vis absorption spectra of 1 d-3 d cover a broad visible-light region (380-572 nm), while DFT and TD-DFT calculations reveal that absorption in this region is dominated by the charge-transfer (CT) transition from the thiophene-centered HOMO to the LUMO of the electron-deficient π-conjugated BF2 -chelated unit and the n→π* and π→π* transitions within the latter unit. The spatial separation of the HOMO and LUMO of these dyes promotes triplet-state generation and self-photosensitizes intramolecular photocyclization in the visible-light region. Three-dimensional time-resolved and steady-state emission spectra of 3 d show that the Norrish-Yang photocyclization takes place within milliseconds with excellent conversion efficiency (96 %).
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Affiliation(s)
- Hui Liu
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Hu Gao
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Sisi Wang
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Shengxin Yao
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Fan Wu
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Kin Shing Chan
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
| | - Zhen Shen
- State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering Nanjing University, Nanjing, 210046, P. R. China
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12
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Kumarasamy E, Ayitou AJL, Vallavoju N, Raghunathan R, Iyer A, Clay A, Kandappa SK, Sivaguru J. Tale of Twisted Molecules. Atropselective Photoreactions: Taming Light Induced Asymmetric Transformations through Non-biaryl Atropisomers. Acc Chem Res 2016; 49:2713-2724. [PMID: 27993011 DOI: 10.1021/acs.accounts.6b00357] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Photochemical transformations are a powerful tool in organic synthesis to access structurally complex and diverse synthetic building blocks. However, this great potential remains untapped in the mainstream synthetic community due to the challenges associated with stereocontrol originating from excited state(s). The finite lifetime of an excited state and nearly barrierless subsequent processes present significant challenges in manipulating the stereochemical outcome of a photochemical reaction. Several methodologies were developed to address this bottleneck including photoreactions in confined media and preorganization through noncovalent interactions resulting in stereoenhancement. Yet, stereocontrol in photochemical reactions that happen in solution in the absence of organized assemblies remained largely unaddressed. In an effort to develop a general and reliable methodology, our lab has been exploring non-biaryl atropisomers as an avenue to perform asymmetric phototransformations. Atropisomers are chiral molecules that arise due to the restricted rotation around a single bond (chiral axis) whose energy barrier to rotation is determined by nonbonding interactions (most often by steric hindrance) with appropriate substituents. Thus, atropisomeric substrates are chirally preorganized during the photochemical transformation and translate their chiral information to the expected photoproducts. This strategy, where "axial to point chirality transfer" occurs during the photochemical reaction, is a hybrid of the successful Curran's prochiral auxiliary approach involving atropisomers in thermal reactions and the Havinga's NEER principle (nonequilibrating excited-state rotamers) for photochemical transformations. We have investigated this strategy in order to probe various aspects such as regio-, enantio-, diastereo-, and chemoselectivity in several synthetically useful phototransformations including 6π-photocyclization, 4π-ring closure, Norrish-Yang photoreactions, Paternò-Büchi reaction, and [2 + 2]- and [5 + 2]-photocycloaddition. The investigations detailed in this Account clearly signify the scope of our strategy in accessing chirally enriched products during phototransformations. Simple design modifications such as tailoring the steric handle in atropisomers to hold reactive units resulted in permanently locked/traceless axial chirality in addition to incorporating multiple stereocenters in already complex scaffolds obtained from phototransformation. Further improvements allowed us to employ low energy visible light rather than high energy UV light without compromising the stereoenrichment in the photoproducts. Continued investigations on atropisomeric scaffolds have unraveled new design features, with outcomes that are unique and unprecedented for excited state reactivity. For example, we have established that reactive spin states (singlet or triplet excited state) profoundly influence the stereochemical outcome of an atropselective phototransformation. In general, the photochemistry and photophysics of atropisomeric substrates differ significantly from their achiral counterparts irrespective of having the same chromophore initiating the excited state reactivity. The ability of axially chiral chromophores to impart stereoenrichment in the intramolecular photoreactions appears to be promising. A challenging endeavor for the "axial to point chirality transfer" strategy is to enhance stereoenrichment or alter chemical reactivity in intermolecular photoreactions. Insights gained from our investigations will serve as a platform to venture into more complicated yet fruitful research in terms of broad synthetic utility.
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Affiliation(s)
- Elango Kumarasamy
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Anoklase Jean-Luc Ayitou
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Nandini Vallavoju
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Ramya Raghunathan
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Akila Iyer
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Anthony Clay
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Sunil Kumar Kandappa
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Jayaraman Sivaguru
- Department of Chemistry and
Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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13
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Zhang MJ, Schroeder GM, He YH, Guan Z. Visible light-mediated decarboxylative amination of indoline-2-carboxylic acids catalyzed by Rose Bengal. RSC Adv 2016. [DOI: 10.1039/c6ra17524d] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A visible-light-induced decarboxylative amination of N-protected indoline-2-carboxylic acids and azodicarboxylate esters catalyzed by Rose Bengal has been developed.
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Affiliation(s)
- Meng-Jie Zhang
- Key Laboratory of Applied Chemistry of Chongqing Municipality
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
- PR China
| | | | - Yan-Hong He
- Key Laboratory of Applied Chemistry of Chongqing Municipality
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
- PR China
| | - Zhi Guan
- Key Laboratory of Applied Chemistry of Chongqing Municipality
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
- PR China
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