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Cong X, Hao N, Mishra A, Zhuo Q, An K, Nishiura M, Hou Z. Regio- and Diastereoselective Annulation of α,β-Unsaturated Aldimines with Alkenes via Allylic C(sp 3)-H Activation by Rare-Earth Catalysts. J Am Chem Soc 2024; 146:10187-10198. [PMID: 38545960 DOI: 10.1021/jacs.4c02144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
The [3 + 2] or [4 + 2] annulation of α,β-unsaturated aldimines with alkenes via β'- or γ-allylic C(sp3)-H activation is, in principle, an atom-efficient route for the synthesis of five- or six-membered-ring cycloalkylamines, which are important structural motifs in numerous natural products, bioactive molecules, and pharmaceuticals. However, such a transformation has remained undeveloped to date probably due to the lack of suitable catalysts. We report herein for the first time the regio- and diastereoselective [3 + 2] and [4 + 2] annulations of α,β-unsaturated imines with alkenes via allylic C(sp3)-H activation by half-sandwich rare-earth catalysts having different metal ion sizes. The reaction of α-methyl-substituted α,β-unsaturated aldimines with alkenes by a C5Me4SiMe3-ligated scandium catalyst took place in a trans-diastereoselective [3 + 2] annulation fashion via C(sp3)-H activation at the α-methyl group (β'-position), exclusively affording alkylidene-functionalized cyclopentylamines with excellent trans-diastereoselectivity. In contrast, the reaction of β-methyl-substituted α,β-unsaturated aldimines with alkenes by a C5Me5-ligated cerium catalyst proceeded in a cis-diastereoselective [4 + 2] annulation fashion via γ-allylic C(sp3)-H activation, selectively yielding multisubstituted 2-cyclohexenylamines with excellent cis-diastereoselectivity. The mechanistic details of these transformations have been elucidated by deuterium-labeling experiments, kinetic isotope effect studies, and the isolation and transformations of key reaction intermediates. This work offers an efficient and selective protocol for the synthesis of a new family of cycloalkylamine derivatives, featuring 100% atom efficiency, high regio- and diastereoselectivity, broad substrate scope, and an unprecedented reaction mechanism.
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Affiliation(s)
- Xuefeng Cong
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Na Hao
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Aniket Mishra
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Qingde Zhuo
- Organometallic Chemistry Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Kun An
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Masayoshi Nishiura
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Organometallic Chemistry Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Zhaomin Hou
- Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Organometallic Chemistry Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Da Silva Pinto S, Davies SG, Fletcher AM, Roberts PM, Thomson JE. Synthesis of (-)-Conduramine A1, (-)-Conduramine A2 and (-)-Conduramine E2 in Six Steps from Cyclohexa-1,4-diene. Org Lett 2019; 21:7933-7937. [PMID: 31518146 DOI: 10.1021/acs.orglett.9b02914] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A method to enable the synthesis of conduramines and their N-substituted derivatives (enantiopure or racemic form) in six steps (five steps for N-substituted derivatives) from cyclohexa-1,4-diene is reported. Key features of this reaction sequence include a preparation of benzene oxide that is amenable to multigram scale, and its efficient ring-opening upon treatment with a primary amine. Epoxidation of the resultant amino alcohols (40% aq HBF4 then m-CPBA) is accompanied by hydrolytic ring-opening in situ to give the corresponding N-substituted conduramine derivatives directly. These may undergo subsequent N-deprotection to give the parent conduramines, as demonstrated by the preparation of enantiopure (-)-conduramine A1, (-)-conduramine A2, and (-)-conduramine E2 (the latter two for the first time). The selectivity of the epoxidation reaction is proposed to be the result of competitive ammonium-directed and hydroxyl-directed epoxidation processes, followed by either direct (SN2-type) or conjugate (SN2'-type) ring-openings of the intermediate epoxides.
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Affiliation(s)
- Solange Da Silva Pinto
- Department of Chemistry, Chemistry Research Laboratory , University of Oxford , Mansfield Road , Oxford OX1 3TA , United Kingdom
| | - Stephen G Davies
- Department of Chemistry, Chemistry Research Laboratory , University of Oxford , Mansfield Road , Oxford OX1 3TA , United Kingdom
| | - Ai M Fletcher
- Department of Chemistry, Chemistry Research Laboratory , University of Oxford , Mansfield Road , Oxford OX1 3TA , United Kingdom
| | - Paul M Roberts
- Department of Chemistry, Chemistry Research Laboratory , University of Oxford , Mansfield Road , Oxford OX1 3TA , United Kingdom
| | - James E Thomson
- Department of Chemistry, Chemistry Research Laboratory , University of Oxford , Mansfield Road , Oxford OX1 3TA , United Kingdom
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Harit VK, Ramesh NG. Ring closing metathesis (RCM) approach to the synthesis of conduramine B-2, ent-conduramine F-2, aminocyclopentitol and trihydroxyazepane. Org Biomol Chem 2019; 17:5951-5961. [PMID: 31166343 DOI: 10.1039/c9ob01010f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The syntheses of conduramine B-2, ent-conduramine F-2, aminocyclopentitol and trihydroxyazepane were accomplished from a common precursor, through a divergent approach using ring closing metathesis (RCM) as the key step. Tri-O-benzyl-d-glucal was converted to 3,4,6-tri-O-benzyl-1,2-dideoxy-2-iodo-1-p-toluenesulfonamido-α-d-mannose. Exposure to NaBH4 in MeOH resulted in a facile 1,2-transposition of the -NHTs group with concomitant glycosylation to give methyl 3,4,6-tri-O-benzyl-2-deoxy-2-p-toluenesulfonamido-β-d-glucoside, which was converted into methyl 6-deoxy-6-iodo-glucoside in three steps. Zinc-mediated Vasella's rearrangement proceeded smoothly to give the pluripotent formyl-olefin, possessing both electrophilic and nucleophilic sites, which was used as a common precursor in our diversity-oriented approach. Vinylation of the carbonyl group followed by RCM and subsequent deprotection resulted in the successful synthesis of conduramine B-2 and ent-conduramine F-2 for the first time. On the other hand, the Wittig reaction of the formyl-olefin affords the diene that undergoes Grubbs' I catalyzed RCM and deprotection/reduction to provide 3-amino-cyclopentan-1,2-diol. Utilizing the nucleophilic site at the nitrogen of the common precursor, base mediated N-allylation was carried out to obtain the corresponding diene that underwent a smooth RCM to afford trihydroxyazepane.
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Affiliation(s)
- Vimal Kant Harit
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
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