O(Cl)[Cl:2].[C:4]1([CH2:10][C:11](O)=O)[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.[OH-].[Na+].O.[NH2:17][NH2:18].[CH3:19][N:20]([CH:22]=O)[CH3:21]>>[CH3:21][N+:20]([CH3:19])=[CH:22][Cl:2].[Cl-:2].[C:4]1([C:10]2[CH:11]=[N:17][NH:18][CH:19]=2)[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1Vilsmeier reagent was prepared by adding 84 mL (0.9 mol) of phosphous oxychloride to 81g (1.1 mol) of DMF with cooling. The reagent was stirred 5 min. and 40.8 g (0.3 mol) of phenylacetic acid in 150 mL of DMF was added dropwise. The mixture was heated at 70° C. for 18 hr, poured onto ice, made basic with 35% aqueous NaOH, filtered free of a solid by-product, and extracted into methylene chloride. The methylene chloride solution was dried over magnesium sulfate and stripped. The residue of 2-phenyl-3-(dimethylamino)acrolein was dissolved in about 350 mL of ethanol and 0.75 mol of hydrazine hydrate was added. The mixture was stirred at room temperature 18 hr and the solid product was filtered off. It was recrystallized from ethanol to yield 35g of 4-phenyl-1H-pyrazole.
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