Singlet oxygen mediated fragmentation of amino alcohols, 1,2-diamines, and amino ketones

Article abstract of DOI:10.1021/ja00052a027

Irradiation of aerated solutions of singlet oxygen sensitizers such as Rose Bengal, Rose Bengal derivative, or palladium tetraphenylporphyrin in the presence of substituted amines (amino alcohols, 1,2-diamines, and amino ketones) results in oxidative fragmentation of the amine in good chemical yield and with low-to-moderate quantum efficiency. For the amino alcohols and 1,2-diamines the reaction course is similar to that initiated by irradiation of electron-transfer "sensitizers" such as thioindigo or cyanoaromatics. In these cases the reaction has been shown to proceed via single electron transfer oxidation of the amine and subsequent cleavage of the amine cation radical. A similar mechanism is proposed for the reaction with singlet oxygen sensitizers in which singlet oxygen initiates reaction by SET oxidation of the amine donors and subsequent reaction from the resulting superoxide-amine cation ion radical pair. For reaction with amino ketones under the same conditions, irradiation results in formation of novel fragmentation products incorporating oxygen. Labeling studies with O-18 enriched oxygen indicate that air is the source of certain of the incorporated oxygen in the products and suggest a mechanism closely related to the other fragmentation processes.