Dilithiated (E)-N-isopropyl-3-tosylacrylamide: a new β-acylvinyl anion equivalent in organic synthesis

Abstract

The dilithiated anion (6) obtained by reaction of (E)-N-isopropyl-3-tosylacrylamide with 2 equiv. of methyl-lithium at –78 °C is a new and efficient β-acylvinyl anion equivalent useful in the synthesis of substituted 3-tosyl-α,β-butenolides (8) by reaction with aldehydes followed by treatment with hydrochloric acid. In the absence of acid the process leads to the γ-hydroxy amide derivatives (7), which undergo thermal isomerization to various 1,4-dicarbonyl compounds, (10)–(12′), depending on the solvent used. The butenolides (8) suffer ring opening on treatment with nucleophiles such as pyrrolidine or methyl-lithium to yield the 1,4-dicarbonyl compound (14) or the 3-tosyl-β,γ-unsaturated acid (15), respectively.