STEREOSELECTIVE SYNTHESIS OF ALPHA-AMINO AND ALPHA-THIO BETA-LACTONESBY CONJUGATE ADDITION OF AMINE AND THIOL NUCLEOPHILES TO ALPHA-METHYLENE BETA-LACTONES AND THEIR DECARBOXYLATION TO ALLYLAMINES AND SULFIDES

The stereoselective, conjugate addition of secondary, cyclic amines (p yrrolidine and piperidine) and mercaptans (thiophenol, isopropyl, and benzyl thiols and beta-mercaptoethanol) to alpha-methylene beta-lacton es 1 and 2 was investigated. The corresponding alpha-(aminomethyl) and alpha-(thiomethyl) beta-lactones 3-5 and 6-10 were obtained in excell ent yields through protonation of the intermediary enolates. In methan ol the trans isomers mere the major products, while considerable amoun ts of the cis isomers were formed in THF and acetone. The decarboxylat ion of these alpha-aminomethyl and alpha-thiomethyl beta-lactones as n eat samples at 180 degrees C produced in excellent yields the correspo nding allyl amines and sulfides 11-13 and 14-18 with retention of the initial beta-lactone geometry. This unprecedented sequence of Michael- type addition followed by decarboxylation, in which the alpha-methylen e beta-lactones serve as allene equivalents, provides a useful alterna tive to the Wittig olefination for the preparation of allylic amines a nd sulfides.