Termination of Mn(III)-Based Oxidative Free-Radical Cyclizations by Addition to Nitriles. Formation of Cyclopentanones and Cyclohexanones

Article abstract of DOI:10.1021/jo00027a056

Mn(III)-based oxidative free-radical tandem cyclizations and annulations can be terminated by addition to nitriles.Cyclopentanones 20a (51percent), 24a (57percent), and 32a (54percent) are formed in good yield.Annulation to give cyclohexanone 32b (41percent) proceeds in moderate yield, although 20b (8percent) and 24b (13percent) are formed in poor yield in tandem cyclizations.Pyridine 39 (15percent) is formed in ethanol by condensation of the enamine tautomer 37 of imine 31a with the oxidation byproduct 33a produced from radical 29a.