Phase-transfer catalyzed synthesis of activated cyclopropanes

Abstract

The phase-transfer catalyzed condensation of diethyl bromomalonate (7d) with Michael acceptors 8–12 leads to cyclopropanes in high yields. More hindered acceptors and other haloesters do not react, while condensation of 7d with crotonaldehyde leads to a 2:1 adduct via a subsequent Darzens condensation. The synthetic potential of the products is also outlined.