Ring closure of 2-thia- and 2-sulfonyl-5-hexenyl radicals

Reductive cyclisation of the 2-sulfonyl-5-hexenyl radical with tributyltin hydride in benzene at 80°C affords a 73:23 mixture of the sulfones derived from 5-exo- and 6-endo- ring closure with a small quantity (4%) of reduced material; under identical conditions, the 2-thia-5-hexenyl radical gives a 70:13:17 mixture of the corresponding sulfides.