HYPERVALENT ORGANOIODINE COMPOUNDS - RADICAL FRAGMENTATION OF OXABICYCLIC HEMIACETALS - CONVENIENT SYNTHESIS OF MEDIUM-SIZED AND SPIRO LACTONES

Photolysis of steroidal models of oxyabicyclic hemiacetals such as 2-oxabicyclo[4.4.0]decan-1-ol, 9-oxabicyclo[4.3.0]nonan-1-ol and 2-oxabicyclo[3.3.0]octan-1-ol, in the presence of (diacetoxyiodo)benzene and iodine afforded, through ring expansion, ten-, nine- and eight-membered lactones, respectively. Spiro lactones of dihydropyran-5-spirocyclohexan-2(3H)-one and dihydrofuran-4-spirocyclohexan-2(3H)-one types were obtained by photolysis of steroidal models of 2-oxabicyclo[2.2.2]octan-1-ol and 7-oxabicyclo[3.2.1]octan-1-ol, respectively.