The cyclization of the title compounds (5a-c) with HCl and HBr has been re-examined. In all cases 5-amino-7-halo-substituted 1, 6-naphthyridines (11a-c and 12a-c) were formed independently of the thermal level and the hydrogen halide employed. The structures of 11a- c and 12a-c were unequivocally established by reaction with hydrazine which afforded the corresponding pyrazolo [3, 4-h][1, 6] naphthyridines (14a-c). The structure of the methoxy ...
