One-pot and step-wise synthesis of thieno[3,2-c]pyridin-4-ones†
Both one pot and step wise synthesis of methyl 3,5-diaminothieno[3,2-c]pyridin-4-one-2-carboxylates 6 have been delineated by the reaction of 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles 3, methyl mercaptoacetate and hydrazine hydrate. During the stepwise synthesis, functionalized thieno[3,2-c]pyran-4-ones 4 were isolated and treated with hydrazine hydrate to afford the desired products. Analogously, condensation–cyclisation of 5 with hydrazine hydrate delivered identical products, thieno[3,2-c]pyridin-4-ones 6, in excellent yields. The structure of isolated product 6 was ascertained by spectroscopic and single crystal X-ray diffraction analyses.