Synthesis of new thieno[2,3‐d]pyrimidines, thieno[3,2‐e]pyridines, and thieno[2,3‐d][1,3]oxazines

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Abstract o‐Aminothiophene dicarbonitrile 1 on neat reaction with cyclic ketones in anhydrous ZnCl2 yielded mixture of fused aminopyridine 3 and iminospirooxazine 4 derivatives. Similarly, pyrimidine derivatives 5 and 8 were obtained by the reaction of this intermediate 1 with formic acid and DMF‐DMA followed by hydrazine hydrate, respectively. The reaction of o‐amino‐thiophene dicarboxamide 2 at ambient temperature with cyclic ketones yielded spiropyrimidine 10 as a sole product in quantitative yield. The regioselective anellated pyrimidine 9, 11, and dihydropyrimidine 12 derivatives were also obtained by the reaction with aromatic aldehydes in presence of piperidine and iodine respectively. J. Heterocyclic Chem., (2012).