An anionic C₃-C₅ ring expansion of β-ketocyclopropanes to cyclopentenols

Abstract

When treated with base, β-ketocyclopropylcarboxylates ring-open to initially afford either cis or trans α, β-unsaturated ketones. The cis isomer undergoes an intramolecular aldol reaction to afford allylic cyclopentenols in high yield and excellent diastereoselectivity. Choice of base is key to a successful outcome.