Selective Photosubstitution Reactions of Tertiary 1-Alkyl-1,1-diarylmethyl Chloride: Simultaneous Formation of Radicals and Carbocations from the Excited State of 1-Alkyl-1,1-diarylmethyl Chloride

Our work has shown for the first time that a preparative and selective photosubstitution of tertiary 1-alkyl-1,1-diarylmethyl chloride is possible upon change of medium. We propose that the tertiary radicals and carbocations are simultaneously generated from the excited singlet state in steady state photoreaction and carbocation additionally are produced from the excited triplet state. Photochemical reactions of arylmethyl halides are interesting and invaluable in synthetic methods because of a possible complement for thermal reactions and in their own rights. In 1963, Zimmerman and Sandel reported that m-methoxybenzyl chloride underwent photochemical solvolysis in aqueous dioxane. Since then, it has been reported that photochemical reactions of a variety of substituted benzyl halides gave solvolysis products and homolysis products. For benzhydryl chloride, steady state and laser flash photolyses have been studied; photochemical reaction of benzhydryl chloride in acetonitrile (AN) containing n-octane gave six products; transient species such as benzhydryl radicals and cations, and excited benzhydryl radical have been identified. Several mechanisms for these reactions have been proposed