carbonate solution the water phase was extracted with ethyl acetate 3 u00d7 100 ml the organic phases were emerged dried over anhydrous magnesium sulfate filtered and then concentrated under reduced pressure the residue was purified through silica column ethyl acetate petroleum ether 1 10 as an eluent to get 18 06 g 1 2 4 dichlorophenyl 1h pyrazole as yellow solid with yield of 84 8 phosphorus oxychloride 225 ml 2 4 mol was added slowly to anhydrous dmf 185 ml 2 4 mol at u2212 5 u00b0 c 0 u00b0 c with mechanical stirring after stirring the mixture for 10 minutes 1 2 4 dichlorophenyl 1h pyrazole 127 8 g 0 6 mol was added to reaction mixture slowly and then reaction was heated at 90 u00b0 c for 15 h after the reaction was over by thin layer chromatography monitoring the reaction mixture was cooled to room temperature then poured into the ice water and neutralized with sodium carbonate the water phase was extracted with ethyl acetate 3 u00d7 150 ml the organic phases were emerged dried over anhydrous magnesium sulfate filtered and then concentrated under reduced pressure the residue was purified through silica column ethyl acetate petroleum ether 1 5 as an eluent to get 98 33 g 1 2 4 dichlorophenyl 1h pyrazole 4 carbaldehyde as white solid 1 2 4 dichlorophenyl 1h pyrazole 4 carbaldehyde 24 3 g 0 1 mol was dissolved in 1501 ml methanol and stirred in ice.