The Singlet Oxygen Oxidation of Chlorpromazine and Some Phenothiazine Derivatives. Products and Reaction Mechanisms.

A kinetic and product study of the reactions of chlorpromazine 1, N-methylphenothiazine 2, N-ethylphenothiazine 3 with 1O2 was carried out in MeOH and MeCN. 1 undergoes exclusive side-chain cleavage whereas the reactions of 2 and 3, in MeOH, afforded only the corresponding sulfoxides. A mechanism for the reaction of 1 is proposed where the first step involves an interaction between singlet oxygen and the side-chain dimethylamino nitrogen. This explains why no side-chain cleavage is observed for 2 and 3.