Some recent work on Schiff bases, imines and iminium salts in synthetic heterocyclic chemistry - a review

This review summarizes the versatile use of Schiff bases, imines and iminium salts for synthesizing a great variety of heterocyclic compounds. Addition reactions of Schiff bases with acid anhydrides, acid chlorides and esters have led to the synthesis of penicillins, β-lactams, pyrrolidinones and piperidinones. Condensations of homophthalic anhydrides with Schiff bases have been the key steps for synthesizing isoquinolinones, protoberberines, 8-oxoberbines, benzophenanthridines and indole alkaloids. Reactions of phthalide anions with iminium salts have been utilized for synthesizing protoberberines, phthalide isoquinolines and related alkaloids. Addition of lithium methyl methylthiomethylsulfoxide to Schiff bases and electroreductive addition of alkyl halides to iminium salts are also discussed