Preparation of N-Heterocycles by Radical Cyclisation of Enamides Mediated by Manganese(III) or Copper(I). A Comparison of Cyclisation Methods

Reaction of enamides with manganese(III) acetate or copper(I) chloride/bipyridine has been investigated. In both cases, an initial 5-endo-trig radical cyclisation reaction took place to produce functionalised pyrrolidinones. The copper(I)-mediated cyclisations were very efficient and bicyclic dienes could be isolated in >80% yield, while the corresponding manganese(III) reactions were generally more problematic, giving related dienes in lower yield (35–52%).