Highly selective SmI2–H2O-promoted radical cyclisation of five-membered lactones

Radicals formed by SmI 2 –H 2 O-mediated electron transfer to the carbonyl group of unsaturated five-membered lactones undergo diastereoselective cyclisation to give cyclohexane-1,4-diols. The use of HMPA as an additive with SmI 2 –H 2 O gave improved conversion and diastereoselectivity in the cyclisations.