Potassium Carbonate → 1-(4-t-Butoxycarbonyl-benzyl)-5-propyl-1H-pyrazole-3-carboxylic acid ethyl ester

Participants

Reaction Steps

To the recovered intermediate (19a) (1.4 g, 5 mmol, 1.0 eq) dissolved into 15 mL DMF, was added 5-propyl-1H-pyrazole-3-carboxylic acid ethyl ester (910 mg, 5.0 mmol, 1.0 eq) and potassium carbonate (0.8 g, 5.5 mmol, 1.1 eq) and the mixture was stirred at room temperature for 16 hours. The mixture was then added to 50 mL of 10% aq. LiCl solution and extracted with 50 mL EtOAc. The organic was dried over MgSO4, and concentrated under reduced pressure to yield intermediate (19b) and its regioisomer in a 1:1 ratio. The recovered regioisomers were dissolved into 25 mL MeOH. To this was added 10 mL of 1M NaOH and the mixture was stirred at room temperature over night. The mixture was acidified with acetic acid and concentrated under reduced pressure. The recovered oil was purified by preparatory HPLC, producing the desired regioisomer of the title compound as a white solid TFA salt after lyophilization (230 mg). 1H NMR (DMSO) 0.89 (t, 3H), 1.52 (s, 9H), 5.71 (s, 2H), 6.71 (s, 1H), 7.15 (d, 2H), 7.83 (d, 2H), 13.28 (br s, 1H).

Provenance & Evidence