Radical-mediated cyclization reactions leading to spiro and [6,6]-fused heterocycles

Regiochemical study of nBu3SnH–AIBN-mediated aryl-radical cyclization of different 3-(2-bromophenyl sul fenylmethyl)coumarins, 3-(2-bromophenylsulfonyl-methyl)coumarins, and 6-[(2-bromophenoxy)methyl]-4-methoxypyran-2-ones have been investigated with the formation of different [6,6]-fused and spirocylic heterocycles. The sulfides and ethers were prepared from 3-chloromethyl coumarin and 6-(bromomethyl)-4-methoxy pyran-2-one with different 2-bromothiophenol and 2-bromophenols under classical alkylation condition. The corresponding sulfones were prepared by oxidation of the sulfides with m-CPBA.