New Methods for Synthesis of α,β-Unsaturated Carboxylic Esters from Carbonyl Compounds Using Monoanions of Dithiocarbonates, and Dianions of Ethyl Mercaptoacetate and Ethyl 2-Mercaptopropionate

Abstract

Abstract The lithium enolates of O-alkyl S-alkoxycarbonylmethyl dithiocarbonates and monothiocarbonates were found to be efficient reagents for the synthesis of α,β-unsaturated esters from carbonyl compounds by single-step procedure. The dianions of ethyl mercaptoacetate and ethyl 2-mercaptopropionate were successfully generated by treatment with 2.2 equivalents of lithium diisopropylamide (LDA) in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) at −78 °C in THF. The dianions so formed are highly reactive toward various electrophiles. The procedure leads to a novel one-pot synthesis of α,β-unsaturated carboxylic esters from carbonyl compounds.