Hydrazine hydrate (1:1) → 4-p-tolylmethanesulfonyl-2H-pyrazol-3-ylamine

Participants

Reaction Steps

7,7-Dimethyl-3-(4-methylbenzyl)sulfonyl)-5-phenyl-4,7-dihydropyrazolo[1,5-a]pyrimidine (4): A slurry of 1.9 g (7.2 mmol) of 3 in 25 mL of ethanol was treated with 0.38 mL (7.9 mmol) of hydrazine monohydrate and heated to reflux for 3 h. The reaction was concentrated in vacuo to give crude 4-p-tolylmethanesulfonyl-2H-pyrazol-3-ylamine as a tan solid. The crude pyrazole, 1.3 g (7.9 mmol) of 3-methyl-1-phenyl-but-2-en-1-one and 2.8 mL (36 mmol) of trifluoroacetic acid was dissolved in 25 mL of 2-methoxyethanol and heated to reflux for 3 days. The reaction was then cooled to room temperature, concentrated in vacuo and dissolved in AcOEt. This solution was washed successively with saturated sodium bicarbonate, water and brine before being dried over sodium sulfate. The solution was filtered, concentrated in vacuo and the resulting crude material was purified by flash chromatography eluting with a 75 to 33% hexanes/AcOEt gradient to give 1.25 g (44%) of the title compound as a powder. 1H NMR (CDCl3) δ 1.67 (s, 6H), 2.13 (s, 3H), 4.26 (s, 2H), 4.81 (d, J=2.0 Hz, 1H), 6.39 (s, 1H), 7.05 (dd, J=8.0, 18.5 Hz, 4H), 7.20 (dd, J=3.7, 7.4 Hz, 2H), 7.36-7.39 (m, 3H), 7.52 (s, 1H). MS Calcd.: 393. Found: 394 (M+H).

Provenance & Evidence