Reduction and Related Reactions of α,β‐Unsaturated Carbonyl Compounds with Metals in Liquid Ammonia

Abstract

Abstract This chapter is concerned with the reduction and related reactions of alpha,beta‐unsaturated ketones by alkali and alkaline earth metals in liquid ammonia. Upon treatment with a metal in liquid ammonia (usually containing an ether co‐solvent) a simple alpha, beta‐unsaturated ketone is converted into the metal enolate corresponding to the saturated ketone. Research during the first half of the 20 th Century revealed that a variety of organic compounds undergo reduction with metals in liquid ammonia but preparative metal‐ammonia reductions of alpha,beta‐unsaturated carbonyl compounds were apparently not described until 1951. In addition to affording a remarkable degree of stereoselectivity, many metal‐ammonia reductions of unsaturated carbonyl systems can be preformed in a variety of functional and protective groupings and the reaction is generally free of the rearrangements sometimes observed when chemical reduction methods are used. The unique features of metal‐ammonia reductions and related reaction have led to their wide application in total synthesis and transformations.