A blue LED-induced three-component coupling of a carbamoyl radical, cyclic enone,
and allylstannane was developed. The use of blue LEDs and diphenyl(2,4,6-trimethylbenzoyl)phosphine
oxide (TPO) as a radical initiator permitted the three-component radical coupling
to proceed with a high chemoselectivity. An elucidation of the mechanism revealed
a pathway for the formation of a tributyltin radical from TPO and allylstannane. This
tandem radical reaction is expected to be applicable in natural-product synthesis.
Key words
radical reaction - coupling - multicomponent reaction - photochemical reaction - total
synthesis - amides