Synthesis and Heterocyclization of 3-Arylaminothiocrotonanilides

Reactions of acetylthioacetanilide with arylamines in acetic acid in the presence of sodium acetate give 3-arylaminothiocrotonanilides in good yields. When treated with -bromoacetophenone in acetone, these products are converted to substituted 4-hydroxy-²-thiazolinium bromides, one of which was dehydrated to obtain the corresponding thiazolium bromide. The structure of the heterocyclization products was confirmed by single crystal X-ray diffraction and NMR study of 2-acetonylidene-3,4-diphenyl-2,3-dihydrothiazole formed by dehydration of the corresponding ²-thiazolinium salt with simultaneous hydrolysis.