Treatment of different aromatic primary amines (7a-b) with chloral hydrate and hydroxylamine hydrochloride under microwave (MW) conditions afforded corresponding isonitrosoacetanilides (6a-b). These intermediate compounds (6a-b) were cyclized in conc.H 2 SO 4 medium to give cyclic amides (5a-b) by means of elcetrophilic aromatic substitution reaction. The microwave (MW) mediated treatment of compound 5a with thiosemicarbazide afforded the corresponding Schiff-base 4a, which undergoes cyclization to give thiadiazoline (1). Beside, compound 4a was also treated with aq KOH solution under MW condition to give triazinothione (3). The Sn-HCl mediated reduction of compound 3 afforded the corresponding 6-aminothione (2). On the other hand, compound 5b was treated with o-phenylenediamine under MW condition to give the corresponding quinoxaline derivative 4b in excellent yield.
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