Triethylborane → Ketorolac methyl ester

Participants

Reaction Steps

A 1.0N solution of triethylborane in hexane (1.6 mL, 1.6 mmoles) was added to a stirred solution of 4-(2-benzoylpyrrol-1-yl)-2-iodobutyric acid methyl ester (IV, 530 mg, 1.3 mmoles) in dimethylsulfoxide (5 mL) under normal air atmosphere. After 1 hour, additional triethylborane (1.0 mL, 1.0 mmole) in hexane was added and the reaction was stirred. After 30 minutes, the reaction was diluted with brine (50 mL) and extracted with diethyl ether (2×50 mL). The organic layer was dried over NaSO4 and evaporated. The crude product was purified by flash chromatography on silica eluting with 1:4 ethyl acetate/hexane to give pure 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acid methyl ester (V, 220 mg, 61%) as an amber oil. 1H NMR (CDCl3): delta 2.75-3.0 (m, 2H); 3.76 (s, 3H); 4.07 (dd, 1H); 4.38-4.61 (m, 2H); 6.09 (d, 1H); 6.81 (d, 1H); 7.4-7.55 (m, 3H); 7.80 (dd, 2H). 13C NMR (CDCl3): delta 30.9, 42.3, 7.4, 52.5, 103.0, 124.8, 127.0,128.0, 128.8, 131.3, 139.1, 142.2, 171.6, 184.8.

Provenance & Evidence