Photo-cleavage of carbon-carbon bond of α-iodocycloalkanones giving ω,ω-dialkoxyalkanoic ester in alcohol

Article abstract of DOI:10.1246/bcsj.73.1645

The irradiation at λ > 300 nm of α-iodocycloalkanones with a high- pressure mercury lamp in alcohols containing a small amount of water afforded the corresponding ω,ω-dialkoxyalkanoic ester (65-88%) by photochemical cleavage of the C(I)-C=O bond at room temperature. In the case of a commercial fluorescent lamp as the irradiating light source, photochemical ring-opening products were also obtained. The irradiation of 2α-iodo-5α- and 4β-iodo-5β-cholestan-3-ones in methanol gave methyl 2,2-dimethoxy-2,3- seco-5α-cholestan-3-oate and methyl 4,4-dimethoxy-3,4-seco-5β-cholestan-3- oate in 78 and 62% yields, respectively. The photochemical behavior of the cleavage reaction of α-iodocycloalkanones is also discussed on the basis of 2-hydroxycycloalkanone as an intermediate.