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Spence KA, Hoffmann M, Garg NK. Total Synthesis of Phenanthroindolizidines Using Strained Azacyclic Alkynes. Org Lett 2023; 25:5044-5048. [PMID: 37379230 PMCID: PMC10460089 DOI: 10.1021/acs.orglett.3c01740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
We report a concise approach to phenanthroindolizidine alkaloids, wherein strained azacyclic alkynes are intercepted in Pd-catalyzed annulations. Two types of strained intermediates were evaluated: a functionalized piperidyne and a new strained intermediate, an indolizidyne. We show that each can be employed, ultimately allowing access to three natural products: tylophorine, tylocrebine, and isotylocrebine. These efforts demonstrate the successful merger of strained azacyclic alkyne chemistry with transition-metal catalysis for the construction of complex heterocycles.
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Affiliation(s)
- Katie A Spence
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Marie Hoffmann
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Neil K Garg
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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Sa Y, Lv X, Yao JY, Lu XY, Wu AB, Shu WM, Yu WC. Tandem Ene/[4 + 2] Cycloaddition Reaction for the Synthesis of 9-Benzylphenanthrenes from Arynes and α-(Bromomethyl)styrenes. J Org Chem 2023. [PMID: 37319302 DOI: 10.1021/acs.joc.3c00051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
A tandem reaction for the synthesis of phenanthrenes from arynes and α-(bromomethyl)styrenes is reported. The transformation proceeds via an ene reaction of α-(bromomethyl)styrenes with arynes, followed by a [4 + 2] cycloaddition reaction. The reaction generates 9-benzylphenanthrene derivatives in moderate to excellent yields.
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Affiliation(s)
- Yun Sa
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Xin Lv
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Jia-Yu Yao
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Xu-Yang Lu
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Ai-Bin Wu
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Wen-Ming Shu
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
| | - Wei-Chu Yu
- Hubei Engineering Research Centers for Clean Production and Pollution Control of Oil and Gas Fields, College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, P. R. China
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Li Q, Hua Y, Tang C, Chen D, Luo M, Xia H. Isolation, Reactivity, and Tunable Properties of a Strained Antiaromatic Osmacycle. J Am Chem Soc 2023; 145:7580-7591. [PMID: 36952602 DOI: 10.1021/jacs.3c00942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
Strain and antiaromaticity in compounds are recognized as two substantial destabilizing features, and consequently, realization of dual destabilizing features in a single molecule is challenging and far more difficult in a single ring. Moreover, transformation of an antiaromatic framework to different antiaromatic or aromatic species is a significant subject in antiaromatic chemistry and has attracted increasing interest. In this work, we isolated a highly strained antiaromatic metallacycle in which a cyclic metal vinylidene unit is embedded. Computational studies revealed its ring strain energies and antiaromatic character and showed that the metal incorporation and the phosphonium substituents play a crucial role in its stabilization. The mechanism of its formation has been illustrated by density functional theory (DFT) calculations and the isolation of a key intermediate. We further discovered diverse reactivities and structural reshuffling of this unusual strained antiaromatic complex according to its two destabilizing characters. We obtained two isomers of metallaindenes fused with oxiranes from the direct oxidation of the metal vinylidene or by nucleophilic addition to an isolated metallacyclocumulene formed by the reaction of metal vinylidene with hydroxide ion, achieving a reconfiguration of the antiaromatic framework. Transformations of the antiaromatic metallacycle by electrophiles to various aromatic metallaindynes have been achieved, and that a condensed Fukui function was employed to confirm the regioselectivity of the electrophilic additions, and the acid/base-induced aromaticity switch along with tunable photophysical properties were investigated. These interesting transformations not only enrich the chemistry of metal vinylidenes and antiaromatics and could also perform potentially as switchable optical materials.
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Affiliation(s)
- Qian Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Yuhui Hua
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Chun Tang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Dafa Chen
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Ming Luo
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Haiping Xia
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
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Hashimoto Y, Tantillo DJ. Mechanism and the Origins of Periselectivity in Cycloaddition Reactions of Benzyne with Dienes. J Org Chem 2022; 87:12954-12962. [PMID: 36121919 DOI: 10.1021/acs.joc.2c01509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory calculations have been used to explore the reaction mechanism of (4 + 2) and (2 + 2) cycloadditions of benzyne with classical dienes. The results indicate the following: (1) (4 + 2) products arise via concerted pathways, (2) (2 + 2) products arise via stepwise pathways with diradical intermediates, and (3) these diradical intermediates are formed via isomerization of carbene intermediates. The origins of periselectivity in these reactions are analyzed using distortion/interaction analysis for the key steps, and they indicate that the tiny distortion in the very early [4 + 2] transition structure, coupled with an entropic favorability, controls selective (4 + 2) cycloaddition.
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Affiliation(s)
- Yoshimitsu Hashimoto
- Department of Chemistry, University of California-Davis, Davis, California95616, United States
| | - Dean J Tantillo
- Department of Chemistry, University of California-Davis, Davis, California95616, United States
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