Synthetic routes to pyrrolizine-1,5-dione derivatives by flash vacuum pyrolysis of amidomethylene derivatives of Meldrum's acid

Abstract

Methoxymethylene Meldrum's acid 1 reacts with 5- and 6-membered lactams in refluxing acetonitrile to give the N-substituted products 9–15. If the reactions are continued for extended times, the Meldrum's acid derivatives decompose to provide enamidoesters e.g.22–24. Flash vacuum pyrolysis of the 5-membered ring products 9–13 provides reasonable yields of the fused pyrrolones 31–35. The constitution of the products is supported by X-ray crystal structures of 10, 12, 19, 32 and 34.