Reactions of quinoxaline with 3-methyl-1-phenylpyrazol-5-one

Quinoxaline during the reaction with 3-methyl-1-phenylpyrazol-5-one in the presence of triethylamine at room temperature in dimethylsulfoxide eliminates o-phenylenediamine and gives 4,4’-methylene-bis(3-methyl-1-phenylpyrazol-5-one) and 1,1,2,2-tetrakis(5-methyl-2-oxo-2-phenyl-1,2-dihydro-3H-pyrazol-4-yl)ethane. The latter was proved to be the intermediate to form the above dipyrazolylmethane derivative.