A new tandem β-fragmentation-cycloperoxyiodination reaction is observed when a homoallylic alcohol is irradiated with visible light in the presence of (diacetoxyiodo)benzene and iodine under an atmosphere of oxygen. A synthetically interesting epidioxyiodide medium-sized ketone is obtained by this method.
The steroidal alcohols 2-cholesten-5 alpha-ol (3), 3-phenyl-2-cholesten-5 alpha-ol (4), and 3 alpha H-2'-oxofuro-[2,3]cholestan-5 alpha-ol (5) were prepared in order to test a new tandem beta-fragmentation-cycloperoxyiodination reaction. The alkoxy radicals generated by irradiation of these alcohols with visible light in the presence of (diacetoxyiodo)benzene, I-2, and molecular oxygen undergo a beta-fragmentation reaction with subsequent peroxidation of the C-radical formed. This peroxy radical is added to conveniently positioned double bonds to give 10-membered cyclic ketones possessing a 1,2-dioxolane group.
Boto Alicia, Betancor Carmen, Prange Thierry, Suarez Ernesto, J. Org. Chem, 59 (1994) N 16, S 4393-4401