Trifluoroacetic acid → (2'-Ethyl-5'-phenyl-1H,2'H-[3,3']bipyrazolyl-5-ylmethyl)-carbamic Acid Methyl Ester

Participants

Reaction Steps

To a room temperature solution of the above-prepared (2′-ethyl-5′-phenyl-1H,2′H-[3,3′]bipyrazolyl-5-ylmethyl)-carbamic acid tert-butyl ester (25 mg, 68 μmoles) in CH2Cl2 (2 mL) was added trifluoroacetic acid (0.5 mL, excess). The resulting solution was stirred at room temperature for one hour, then concentrated and azeotroped with acetonitrile (3×) in vacuo. To the resulting crude deprotection product in acetonitrile was added triethylamine, then 1-methoxycarbonyl imidazole (26 mg, 204 μmoles) and the mixture was heated to 90° C. for two hours. The reaction was then cooled to room temperature, diluted with ethyl acetate and 1 M NaHSO4, and stirred vigorously for 20 minutes. The organic phase was washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo. Flash chromatography (silica gel, hexanes/ethyl acetate gradient) provided the title compound as a white solid. 1H NMR (CDCl3, 400 MHz): 7.87 (d, 2H); 7.41 (dd, 2H); 7.37 (dd, 1H); 6.75 (s, 1H); 6.42 (s, 1H); 5.30 (dd, 1H); 4.68 (q, 2H); 4.40 (d, 2H); 3.73 (s, 3H); 1.51 (t, 3H).

Provenance & Evidence