Wang D, Crowe WE. One-carbon bridge stereocontrol in robinson annulations leading to bicyclo[3.3.1]nonanes.
Org Lett 2010;
12:1232-5. [PMID:
20180523 DOI:
10.1021/ol1000878]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The one-carbon bridge stereochemistry of bicyclo[3.3.1]nonane products formed in the Robinson annulation reactions of 2-substituted cyclohex-2-enones was investigated. In contrast to previous reports, it was found that the major diastereomer formed places the one-carbon bridge substituent anti to the beta-keto ester/amide unit introduced in the Robinson annulation. This stereoselectivity appears to be kinetically controlled. In the case of a beta-keto amide product derived from carvone, it was demonstrated, through base-catalyzed epimerization, that thermodynamic control favors the syn isomer.
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