Preparation of 3-substituted 10-methylphenothiazines

Lithiation at the C-3 position of 10-methylphenothiazine can be achieved by a (BuLi)-Li-s-Br exchange reaction starting from 3-bromo-10-methylphenothiazine. Reaction of the lithiated species with different electrophiles gives rise to different new and well known compounds which due to their radical properties are important enzyme enhancers, The described procedure gives moderate to high yield and easy access to C-3 substituted derivatives.