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Published on: February 7, 2019
Enantioselective synthesis of bicylco[3.2.1]octan-8-ones using a tandem Michael-Henry reaction
Derong Ding1, Cong-Gui Zhao, Qunsheng Guo
1Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
Abstract:
Bicyclo[3.2.1]octan-8-ones have been prepared from a tandem Michael-Henry reaction between cyclohexane-1,2-diones and nitroalkenes using a quinine-derived thiourea as the catalyst. Although four stereogenic centers were created during the reaction, only two diastereomers were obtained in good diastereoselectivity and high enantioselectivity (92-99% ee). When 3-methylcyclohexane-1,2-dione (R(1) = Me) was used as the substrate, only the regioisomeric product of the corresponding thermodynamic enolate was obtained.
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Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

