Synthesis and Reactivity of 2-(Thiophen-2-yl)naphtho[2,1-d][1,3]thiazole

The condensation of naphthalen-2-amine with thiophene-2-carbonyl chloride in propan-2-ol gave N-(naphthalen-2-yl)thiophene-2-carboxamide whose treatment with excess P2S5 in anhydrous toluene afforded the corresponding thioamide. Oxidation of the latter with potassium ferricyanide in alkaline medium led to the formation of 2-(thiophen-2-yl)naphtho[2,1-d][1,3]thiazole. The cyclization involving C1 of the naphthalene ring was substantiated by quantum chemical calculations. The title compound was subjected to electrophilic substitution reactions, including nitration, bromination, formylation, and acylation, in which the electrophile entered exclusively position 5 of the thiophene ring.