One-Pot Synthesis of Novel Functionalized Fused Pyridine Derivatives via Consecutive Pyrrolidine Ring-Closure/Ring-Opening/Formal Aza-Diels–Alder Reactions

In this article, we report a highly regioselective method for the synthesis of new fused pyridine derivatives2,3-disubstituted quinolines and 1,2-dihydro-3H-pyrazolo­[3,4-b]­pyridin-3-one derivatives. The method is based on the reaction of 1,1-diethoxybutane derivatives with aromatic and heterocyclic nucleophiles. The isolated compounds are similar to the products formed as a result of the Debner–Miller reaction. However, we have shown that the interaction of 1,1-diethoxybutane derivatives with (hetero)­aromatic amines proceeds according to a mechanism different from that of the Doebner–Miller reaction. The proposed method is distinguished by the possibility of obtaining a wide range of substituted quinolines and 1,2-dihydro-3H-pyrazolo­[3,4-b]­pyridin-3-one derivatives in one step, the absence of the need to use expensive metal-containing catalysts, and a high product yield.