P. Hradil et al., CYCLIZATION OF PHENACYL 2-([2,2-DI(ETHOXYCARBONYL)VINYL]AMINO)BENZOATE, Collection of Czechoslovak Chemical Communications, 63(4), 1998, pp. 520-524
Reaction of phenacyl anthranilate (1) with diethyl (ethoxymethylidene)
malonate afforded phenacyl 2-{[2,2-di(ethoxycarbonyl)vinyl]amino}benzo
ate (2) which on heating in polyphosphoric acid underwent degradation.
Thermal cyclization of 2 in diphenyl ether gave phenacyl carbonyl)-4-
oxo-1,4-dihydroquinoline-8-carboxylate (ib). The phenacyl group did no
t cyclize even on prolonged heating. at 250 degrees C. Heating in sulf
uric acid resulted in hydrolysis of the ethyl ester under formation of
cyloxy)carbonyl]-1,4-dihydroquinoline-3-carboxylic acid (6). The stru
cture of 4 was confirmed by an independent synthesis.