Radical-mediated cyclization reaction — Regioselective synthesis of pyrimidine- and coumarin-annulated [6,6]-fused oxygen heterocycles

The n-Bu3SnH-AIBN mediated aryl radical cyclization of various 8-[(2-bromophenoxy)methyl]-1,3-dimethyl-2,3,4,6-tetrahydro-1H-pyrano[3,2-d]pyrimidine-2,4-diones and 1-[(2-bromophenoxy)methyl]-3,5-dihydropyrano[2,3-c]coumarins was investigated with the formation of [6,6]-fused oxygen heterocycles as a single regioisomer.Key words: n-Bu3SnH-AIBN, aryl radical cyclization, 6-endo-trig, oxygen heterocycles, coumarin derivatives, pyrimidine derivatives.