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

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.