A study of three reactions leading to isomeric 2-(N,N-disubstituted amino)thiazol-5-yl ketones

Abstract

N-Imidoyl-N,N-disubstituted thioureas react with α-halogeno ketones in the presence of triethylamine to give the expected 2-(N,N-disubstituted amino) thiazol-5-yl ketones in high yield. The corresponding reactions of N-acyl-N,N-disubstituted thioureas lead to mixtures of these products and isomers which arise from rearrangement between cyclic intermediates. Mixtures of the isomeric thiazolyl ketones are also formed by treating N,N-disubstituted thioureas with 2-bromo 1,3-diketones. The mixtures from the second and third routes contain the same products but in significantly different proportions. A mechanistic scheme which accounts for the main findings was developed.

During the work 40 new 2-(N,N-disubstituted amino)thiazol-5-yl ketones were prepared and their structures rigorously established; characteristic mass spectral fragmentation patterns were particularly useful in identifying the substituents at positions 4 and 5 of the thiazole ring.