REGIOSELECTIVITY IN PHOTOCHEMICAL CHLOROCARBONYLATION OF CARBONYL-COMPOUNDS

Photochemical chlorocarbonylation of a series of cyclic and acyclic carbonyl compounds shows remarkable regioselectivity and gives beta- or gamma-substituted products in reasonable yields. Irradiation of cyclopentanone in oxalyl chloride followed by esterification with methanol gave methyl 3-oxocyclopentanecarboxylate (4). Similarly, photochemical chlorocarbonylation of cyclobutanone yielded methyl 3-oxocyclobutanecarboxylate (6). Application of the chlorocarbonylation reaction to 3-pentanone gave methyl 4-oxohexanoate (8) and dimethyl 4-oxopimelate (9). When a mixture of 3-methylbutanoic acid and oxalyl chloride was irradiated, dimethyl 3-methylglutarate (11) was obtained after methanolysis. A kinetically-controlled mechanism for the photochemical process was deduced.