Photolysis of Alcohols and Alkanones in Acetone Solutions. Photochemical [2+2]Cycloaddition Reaction between Acetone and Aliphatic Enols

Transient enols including those of acetaldehyde, acetone, cyclopentanone, 3-pentanone, 2,4-dimethyl-3-pentanone, 2-butanone, and 2-methyl-3-pentanone were trapped photochemically with acetone via a [2+2]cycloaddition and isolated as corresponding 3-oxetanols in reasonable yields in the photolysis of six different secondary alcohols and two alkanones, 3-octanone and hexanal, in acetone solutions. The trapping experiments indicated the photodehydrogenation of unsymmetrical alcohols, 2-butanol and 2-methyl-3-pentanol, in acetone to be highly regioselective in preference for the formation of the less alkylated enol.