Isopropylamine → Ethyl-5-phenyl-4-(2-pyridinyl)-1H-pyrazole-1-acetate

Participants

Reaction Steps

A solution of 26 g (0.132 mol) of 1-phenyl-2-(2-pyridinyl)ethanone and 19.3 mL (0.145 mol) of dimethylformamide dimethylacetal in 100 mL of methyl t-butyl ether was refluxed 4 hr. Because TLC on silica gel with 10% isopropylamine in ethyl acetate showed little reaction, another 20 mL of DMF dimethylacetal was added and the solution refluxed a further 6 hr. The solvent was stripped and the resulting crude, oily β-ketoenamine was dissolved in 400 mL of ethanol. The ethanol solution was heated to 40° with 22 g (0.143 mol) of ethyl hydrazinoacetate hydrochloride for about 1.5 hr. The solvent was stripped, and the resulting impure product was dissolved in a small amount of methylene dichloride and applied to a column of 850 g of silica gel. The column was eluted with 2:1 hexane-ethyl acetate to yield 25 g of yellow solid product, mp 98°-100° C. after evaporation of the solvent.

Provenance & Evidence