Tetramethoxypropane → 1-(4-chlorophenyl)-1H-pyrazole

Participants

Reaction Steps

A solution of 4-chlorophenylhydrazine hydrochloride (2.02 g, 11.3 mmol), 1,1,3,3-tetramethoxypropane (2.00 mL, 12.1 mmol) and sodium acetate (1.00 g, 12.2 mmol) in acetic acid (25 mL) is heated to gentle reflux overnight. The solution is cooled and poured into water (125 mL). Solid sodium bicarbonate is added in portions until the pH of the mixture is slightly basic. This is then extracted twice with ethyl acetate (125 mL), and the extracts are washed with brine, combined, dried over anhydrous magnesium sulfate, filtered and evaporated to afford 1-(4-chlorophenyl)pyrazole in two crops (1.13 g+0.24 g, 7.65 mmol, 68%). m.p. 50-53° C. TLC RF 0.19 (10:90 ethyl acetate-hexane), 1H NMR (300 MHz, CDCl3): δ 7.89 (1H, dd, J=2.4, 0.6 Hz), 7.72 (1H, d, J=1.5 Hz), 7.64 (2H, d, J=8.7 Hz), 7.42 (2H, d, J=8.7 Hz), 6.47 (1H, dd, J=2.4, 1.8 Hz). MS (ES+): m/e 182 (3), 181 (34), 180 (6), 179 (100).

Provenance & Evidence