Nitrogen bridgehead compounds. Part 74. Cyclization of 2-(2-pyridylaminomethylene)succinates in ethanolic sodium ethoxide. Part 2. Michael addition of pyridyldihydropyrrolones

Abstract

2-(2-Pyridylaminomethylene)succinates, which in ethanolic sodium ethoxide solution yielded equilibrium mixtures of the pyridopyrimidines (3) and the pyridyldihydropyrrolones (5) and (6), within 15 min, furnished a dihydropyrrolone dimer as the main product on longer ( 2 h) reaction. The dimer had the unusual 4,4′-connection between the five-membered rings, and was shown to be the pure trans-diastereoisomer (7); it is considered to be formed by a Michael addition reaction of the pyrrolones (5) and (6). These longer reactions are accompanied by hydrolytic processes.