The reactions of some bromo-derivatives of compounds having reactive methylene groups with thioureas, and of some resultant thiouronium salts with base

Abstract

Whereas α-bromocarbonyl compounds react with thiourea to give thiazole derivatives, bromomalononitrile and bromobis(phenylsulphonyl)methane underwent protodebromination. With N,N,N',N'-tetramethylthiourea many of the bromo-compounds gave thiouronium salts but protodebromination sometimes supervened. N,N'-Disubstituted thioureas provided examples of salt formation, protodebromination and cyclisation reactions. The only thiouronium salt to provide an ylide on treatment with base was the S- [bis(phenylsulphonyl)methyl]-N,N,N',N'-tetramethythiouronium bromide. N,N'-Disubstituted salts gave isothioureas rather than ylides. Thiouronium dicyanomethylide underwent cyclisation rather than a Wittig reaction when heated with p-nitrobenzaldehyde, and the aldehyde condensed with the resultant 2-aminothiazole.