Synthetic studies on cyclobuta[a]indanes: stereocontrolled access to C9-substituted derivatives.

We report the preparation of novel ethyl cyclobuta[a]indane derivatives of pharmacological interest. The synthesis of compounds 5 was used as a model to study stereocontrolled access to C9-substituted cyclobutane from the corresponding cyclobutanone 1. Progress was made on two complementary aspects: (1) catalytic hydrogenation from the appropriate cyclobutene precursors; and (2) delivery of the C9 substituent through an intramolecular process.