Isothipendyl'), pr~thipendyl',~), pipazethate'), and pervetral') are azaphenothiazine derivatives which are presently used as drugs. Although literature is filled5-I4) with numerous patents and publications on azaphenothiazines and azaphenoxazines, very little efforts have been made to synthesize substituted azaphenoxazines and azaphenothiazine derivatives. Recently derivatives of 2-chloro-1,4-diazaphenothiazine showed a promising tranquilizing activityi4) in comparison to substituted 1,4-diazaphenothiazine derivatives. Thus, introduction of a new substituent into the 1,4-diazaphenothiazine markedly enhanced the biological activity. These results encouraged us to develop an efficient highyield synthesis of various substituted 12H-quinoxalino- were prepared by the base-catalyzed condensation of 4 with 1 a and the 2-aminophenol 2i in aqueous dimethylformamide. We have developed a new method for the synthesis of various substituted 12H-quinoxalino[2,3-b][1,4]benzothiazines 7a -h using the more stable zinc mercaptides 3a-h of la-h. The reaction of 4 with 1 a -h or 3a -h in the presence of dimethylformamide afforded 7a -h in excellent yields. Similarly, the reaction of 4 with 2i -k under the same conditions provided 7i -k. The reaction of 4 with 1 a -h o r 3a -h in dilute acid using alcohol as solvent also afforded 7a-h in Since no reaction takes place in the absence of bases, attack of the amino group is not involved in the reaction. We assume, that a mercaptide group attacks a chlorine-