Novel and convenient synthesis of polyfunctionalized quinolines, quinolones and their annulation reactions

The reaction of α-aroylketene dithioacetals with esters of o-aminobenzoic acid under different conditions afforded preferentially 2-methylthio-3-aroylquinolones and 2-anilino-3-aroylquinolines through, respectively, α-aroylketene N,S-acetal and α-aroylketene aminal intermediates. The annulation reaction of 2-methylthio-3-aroylquinolones with hydrazine gave both pyrazolo[3,4-b]quinolone and pyrazolo[4,3-c]quinoline, the selectivity being determined by the reaction conditions employed. Intramolecular cyclocondensation of 2-anilino-3-aroylquinolines produced quino[2,1-b]quinazolines in high yield.