Hydrochloric Acid → 7-Cyclohexyl-6-(4-methylsulfanylphenyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A mixture of 14 mg (0.085 mmol) of 4-methylsulfanyl-phenylboronic acid, 2 mg (0.0028 mmol) of Pd catalyst, and 45 mg (0.213 mmol) of potassium phosphate was placed into a 4 mL vial. To this mixture 25 mg (0.077 mmol) of 6-bromo-7-cyclohexyl-pyrazolo[1,5-α]pyrimidine-3-carboxylic acid ethyl ester in 1.5 mL of 1,4-dioxane was added, the resulting mixture was flushed with argon and stirred at 80° C. (oil bath) overnight. The reaction mixture was then diluted with ethyl acetate, filtered through a small pad of Celite, and evaporated (savant) to give a residue (crude coupling product). This residue was dissolved in 1 mL of tetrahydrofuran (THF) and treated with 0.5 mL (0.5 mmol) of 1 M LiOH solution, and the resulting mixture was stirred at rt overnight. Since analysis by thin layer chromatography (TLC) revealed that the reaction was not complete, the mixture was then shaken at 55° C. (sand bath) for 15 h. The reaction mixture was diluted with ethyl acetate, and acidified with 1 M HCl solution to pH=2. The organic layer was separated and concentrated (savant) to give a residue which was purified via reverse-phase chromatography (using Gilson) to afford (after lyophilization) 14 mg (56% overall yield) of 7-cyclohexyl-6-(4-methylsulfanyl-phenyl)-pyrazolo[1,5-a]pyrimidine-3-carboxylic acid (472) as a solid as indicated by 1H NMR; LC-MS—calcd for C20H21N3O2S [M++H]+: 368.14, found: 368.2.

Provenance & Evidence