Radical Anions from Urea-type Carbonyls: Radical Cyclizations and Cyclization Cascades.

Radical anions generated from urea carbonyls by reductive electron transfer are exploited in carbon-carbon bond formation. New radical cyclizations of urea radical anions deliver complex nitrogen heterocycles and, depending upon the proton source used in the reactions, a chemoselective switch between reaction pathways can deliver two heterobicyclic scaffolds. A computational study has been used to investigate the selectivity of the urea radical processes. Furthermore, radical cyclization cascades involving urea radical anions deliver unusual spirocyclic aminal architectures.