Introduction

Abstract

In the late nineteenth and early twentieth centuries the discoverers of carbon-carbon bond-forming reactions which depended on the presence of carbonyl groups (Michael, Claisen, Knoevenagel, et al.) laid the foundations of modern synthetic organic chemistry, and, despite an explosion in the number of new reagents and reactions in recent years, the carbonyl group still remains one of the most versatile functionalities available to the organic chemist.⁽¹⁾ The importance of this simple group derives not only from its own inherent reactivity, being susceptible to both nucleophilic attack at carbon and electrophilic attack at oxygen, but also from the polarizing effect it has on neighboring atoms and functional groups, particularly its ability to stabilize an adjacent carbanion by charge delocalization into the C = O double bond.