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

Regiochemical study of "Bu3SnH-AIBN-mediated aryl-radical cyclization of different 3-(2-bromophenylsulfenylmethyl)coumarins, 3-(2-broi-nophenylsulfonyl-methyl)coumarins, and 6-[(2-broinophenoxy)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 cournarin and 6-(bromoinethyl)-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.