In this work, we have studied the reaction of substituted 2-thiocyanoacetophenone and hydrazine hydrate as a novel and simple pathway for the preparation of the substituted 1,4,5-thiodiazepine ring system. The mechanism of this reaction revealed that in the initial step condensation of hydrazine with carbonyl groups of substituted 2-thiocyanoacetophenons 2a–2f gives the corresponding substituted aromatic dithiocyano azide intermediates which in turn undergo cyclization to1,4,5-thiadiazepines in the presence of hydrazine. This cyclization is a novel method for the preparation of sulfide bond from the reaction of hydrazine and a dithiocyano intermediate. An account of the reaction mechanism is given.

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