Three-component cyclocondensations. Two methods for the efficient preparation of 5-aminothiazolium salts via the reaction of isocyanides either with dimethylthioformamide and imino chloro sulfides or benzaldimines and aryl chlorothioformates

Abstract

Treatment of imino chloro sulfides with dimethylthioformamide and isocyanides at room temperature provides selectively the 5-amino-4-(dimethylamino)-2-(methylthio) (or phenylthio)thiazolium salts. Similarly, the reactions of p-tolyl chlorothionoformate and phenyl chlorodithioformate with a mixture of benzaldimine and isocyanide afford rapidly the 5-amino-4-phenylthiazolium salts. We suggest that these reactions involve the N-(thiocarbonyl)formamidinium and benzylideniminium chlorides as transient intermediates, which are trapped by isocyanides according to a [1+4] cycloaddition process. The structure of the thiazolium salts and some of their reactivities are discussed