Unexpected result of KOH—MeOH-promoted Thorpe—Ziegler heterocyclization of N-[(3-cyanoquinolin-2-yl)thio]acetylphenothiazines

Abstract

The reaction of 10-(chloroacetyl)phenothiazine with 4-aryl-2-thioxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitriles in DMF under mild conditions (25 °C, 1 h, KOH—MeOH) affords unsubstituted phenothiazine and methyl 3-amino-4-aryl-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxylates. The plausible reaction mechanism is discussed. The structures of the new compounds were confirmed by IR and NMR spectroscopy and X-ray diffraction analysis.