Preparation of 4-substituted 10-ethylphenothiazines

Abstract

Under appropriate reaction conditions 10-ethylphenothiazine 1 undergoes lithiation at C-4 using an excess of sec-butyllithium–N,N,N′,N′-tetramethylethane-1,2-diamine in diethyl ether. Reaction of the lithiated intermediate with a variety of carbon, halogen, sulfur and silicon electrophiles affords several new 4-substituted 10-ethylphenothiazines 3a–i in good yields.