ChemInform Abstract: Syntheses and Uses of Azetidiniminium Salts

Abstract

Tertiary amides are readily converted into iminium salts which react with imines in the presence of triethylamine to give azetidiniminium salts. Upon hydrolysis, thiolysis or aminolysis these are transformed into the corresponding -lactams, azetidinethiones or azetidinimines. Chiral azetidiniminium salts have been obtained in high optical purity from chiral iminium salts and imines. A new application of the Baeyer-Villiger oxidation has been found : it allows the conversion of azetidiniminium salts into oxazolidinones. Preliminary results on a new potential asyninetric synthesis of amino alcohols and amino acids are described. INTRODUCTION Several decades after the discovery of penicillin, the search for more effective antibiotics still provides the incentive for continuing synthetic studies of new monoand bicychic-lactams. Among a plethora of structural variations, only a few involve the replacement of the carbonyl group of the -lactam by related electrophilic groups (ref. 1). Several years ago we felt that there was a need to develop practical synthetic approaches toward these analogs of -lactams. This lecture will sunmarise our present knowledge on the synthesis and applications of azetidiniminium salts. SYNTHESES OF AZETIDINIMINIUM SALTS The synthetic strategy for the preparation of azetidiniminium salts follows very closely the one often utihised for -lactams. It involves the reaction of an imine with electrophihic reagents derived from tertiary amides (Scheme 1). These are readily converted Scheme I U / /CHCN