Borane;tetrahydrofuran → ethyl 3-tert-butyl-1-(2-(dimethylamino)ethyl)-1H-pyrazole-5-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a solution of ethyl 3-tert-butyl-1-(2-(dimethylamino)-2-oxoethyl)-1H-pyrazole-5-carboxylate (1.16 g, 4 mmol) in THF (10 mL) was added 1M borane/THF (12 ml, 12 mmol) at 0° C. under Ar and stirring continued for 12 h at 60° C. The mixture was cooled to 0° C., quenched with 3M HCl solution and heated to 60° C. for 30 min. The mixture was basified with solid NaHCO3 to pH around 8 and the product was extracted with CHCl3 (2×30 ml). The combined organics were washed with brine, dried (Na2SO4) and concentrated in vacuo provided crude product. Purification by silica gel chromatography provided ethyl 3-tert-butyl-1-(2-(dimethylamino)ethyl)-1H-pyrazole-5-carboxylate as a pasty mass (0.47 g, 43% yield). 1H NMR (400 MHz, MeOH-d4): δ 6.73 (s, 1H), 4.66 (t, J 6.8 Hz, 2H), 4.35 (q, J=7.2 Hz, 2H), 2.80 (t, J= 7.2 Hz, 2H), 2.34 (s, 6H), 1.38 (t, J=7.2 Hz, 3H), 1.31 (s, 9H); MS (ESI) m/z: 268.2 (M+H+).

Provenance & Evidence