Abstract All the possible 1-and 3-monomethyl, monophenyl, dimethyl, diphenyl, and methylphenyl-1H-pyrazolin-5-ones have been condensed with o-aminobenzaldehyde. In some cases (but not all) 1-H-pyrazolo [3, 4-b] quinolines (10) are formed together with a variety of other products. The balance between formation of hydrazone 11 and the ring- closed 10 is discussed, as is the formation of other products obtained in these ...