12H-benzo [b] phenothiazine-6. ll-dione (X), we were unable to reduce X beyond the dihydroxy stage, and, on working up the reaction mixture, the latter compound mas oxidized back to X. In all cases, cyanoethylation of the linear compounds was carried out without difficulty. Compounds T'IIa and VIIb gave XIa and XIb, respectively, and T'IIc yielded the dicyanoethylated product (XII). The angular IXa gave 7H-benzo-[c] phenothiazine-'7- ...