Diastereoselective syntheses of substituted cis-hydrindanones featuring sequential inter- and intramolecular Michael reactions.

The hydrindane (bicyclo[4.3.0]nonane) structural motif (1) and related cis-1-hydrindanone skeleton (2) are common substructures in many natural products. Herein, we describe efficient access to substituted cis-1-hydrindanones enabled by a sequence of Michael reactions. A copper-catalyzed intermolecular Michael addition of a cyclic silyl ketene acetal to a β-substituted-α-alkoxycarbonyl-cyclopentenone enables construction of a quaternary center and is followed, after incorporation of an additional Michael acceptor, by a second, intramolecular addition of a nucleophilic β-ketoester. This strategy affords stereoselective access to substituted bicyclic cis-hydrindanone ring systems containing up to three contiguous stereocenters.