We describe in this article the results of investigations involving the reaction of benzoyl isothiocyanate I with acetoacetanilides IIa, IIb.

The active methylene reagents la-d reacted with phenyl isothiocyanate in basic DMF at room temperature to yield the non-isolable 1:l adducts 2a-d. In-situ cyclization of the latter with y-bromoacetoacetanilides afforded the 2,3-dihydrothiazoles 3a-h. The reactivity of 3a towards a variety of chemical reagents has been undertaken. Thus, on smooth alkaline hydrolysis, with benzaldehyde and with benzenediazonium chloride, the thiazole derivatives 4, 5, 7 and 9 were obtained. With acetylacetone, malononitrile, ethyl cyanoacetate and cinnamonitriles it gave the corresponding thiazol-4-yl-pyridine derivatives 10, 11, 12, and 13 respectively. 13 Reacted with hydroxylamine hydrochloride and phenyl hydrazine to give the corresponding fused ring systems 15 and 17 respectively.

The active methylene compounds - derivatives of malonic or 4-oxobutanoic acid - reacted with carbon disulfide in dimethyl formamide containing potassium hydroxide to yield the non-isolable dipotassium disulfide intermediates. The latter were cyclized by α-haloketones to give thiophene, thieno[2,3-b]thiophene, thieno[3,2-c]pyrazole and thieno[3,2-b]pyridine derivatives. The reactivity of the products toward various reagents was studied.

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