Methanol → 3-(3-Cyclopentyloxy-4-methoxybenzylamino)-4-hydroxymethylpyrazole

Participants

Reaction Conditions

Reaction Steps

Pure 3-(3-cyclopentyloxy-4-methoxybenzylamino)-4-pyrazolecarboxylic acid (compound 3) (1.32 g, 4.0 mmol) was dissolved in 50 ml of THF and cooled to -15° C. under nitrogen. Borane-tetrahydrofuran (30 ml of 1M solution, 30 mmol) was added over 30 minutes and the resulting solution was stirred for 72 hours at room temperature. Methanol (30 ml) was added to the reaction and the solvent was evaporated under reduced pressure. The residue was treated with 160 ml of methanol and evaporated again. The crude product was treated with 30 ml of 10% aqueous ammonia and some brine and then extracted with three 50 ml portions of ethyl acetate. Evaporation of the solvent afforded 1.1 g of crude 3-(3-cyclopentyloxy-4-methoxybenzylamino)-4-hydroxymethylpyrazole which was purified by flash chromatography on 30 g of flash chromatography silica gel. Elution with ethyl acetate/hexane (1:4) afforded a small amount of material which was discarded. Elution with 60 ml of 1:1 ethyl acetate/hexane gave 600 mg of 3-(3-cyclopentyloxy-4-methoxybenzylamino)-4-hydroxymethylpyrazole which was recrystallized from 2 ml of toluene to give 500 mg of pure 3-(3-cyclopentyloxy-4-methoxybenzylamino)-4-hydroxymethylpyrazole (compound 4) mp 129-130° C.

Provenance & Evidence