A solution of 4-hydroxy-1-methyl-3,5-diphenylpyrazole (10 g, 0.04 mole), potassium t-butoxide (4.5, 0.04 mole) and dry DMF (150 ml) is stirred and heated to 60° C. The green fluorescent solution is cooled to room temperature and p-chloronitrobenzene (6.0 g, 0.038 mole) is added. The dark green solution is heated at 60° C for 24 hours and then poured into water, made alkaline with 1N sodium hydroxide and extracted with ether. The ether layer is separated, washed well with water, dried and stripped in vacuo to give a bright yellow solid 12.9 g (86.5%), m.p. 85° C to 110° C. The solid is chromatographed on silica gel with benzene to give a yellow crystalline solid 11.3 g, m.p. 74° C to 100° C. Recrystallization from methanol (185 ml) affords white crystals 5.5 g (37%) m.p. 120° C to 122° C.
