Dearomatizing radical cyclizations and cyclization cascades triggered by electron-transfer reduction of amide-type car-bonyls

Highly selective dearomatizing radical cyclizations and cyclization cascades, triggered by single electron-transfer to amide-type carbonyls by SmI2-H2O-LiBr provide efficient access to unprecedented spirocyclic scaffolds containing five stereocenters with high diastereocontrol. The first dearomatizing radical cyclizations involving radicals derived from the amide carbonyls by single electron-transfer take place under mild conditions and engage a range of aromatic and heteroaromatic systems present in the barbiturate substrates. The radical cyclizations deliver new polycyclic hemiaminals or enamines selectively, depending on the conditions employed, that are based on a medicinally proven scaffold and can be readily manipulated.