Sayan Ray, S. Mukherjee
Jun 24, 2022
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Journal
Synlett
Abstract
Bicyclo[4.1.0]heptane framework, consisting of cis-fused cyclopropane and cyclohexane rings, is found in several bioactive compounds. Given the symmetry of this core, catalytic desymmetrization can be considered as the most straightforward strategy for their enantioselective synthesis. Known desymmetrization reactions of meso-bicyclo[4.1.0]heptane derivatives proceed with the opening of the cyclopropane ring. We now report the first ring-retentive desymmetrization of a bicyclo[4.1.0]heptane derivative, namely meso-cyclopropane-fused cyclohexene-1,4-diones through formal C(sp2)‒H alkylation using nitroalkane as the alkylating agent. This reaction is catalyzed by a dihydroquinine-derived bifunctional tertiary aminosquaramide and generates the products with up to 97:3 er. An application of this reaction is demonstrated by the first catalytic enantioselective synthesis of the natural product (–)-car-3-ene-2,5-dione.