Lithium Hexamethyldisilazide → 1,4-Piperidinedicarboxylic acid, 4-[[5-bromo-1-(1,1-dimethylethyl)-1H-pyrazol-4-yl]methyl]-, 1-(1,1-dimethylethyl) 4-ethyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of 1-tert-butyl 4-ethyl piperidine-1,4-dicarboxylate (0.37 mL, 1.47 mmol) in THF (15 mL) was cooled to −78° C. and then treated with lithium bis(trimethylsilyl)amide (1.48 mL, 1.48 mmol, 1 M toluene), dropwise. The reaction was stirred 15 minutes at −78° C., warmed to 0° C. for 30 minutes and then cooled back to −78° C. A solution of 5-bromo-4-(bromomethyl)-1-tert-butyl-1H-pyrazole (335 mg, 1.13 mmol) in THF (10 mL) was added, the mixture was stirred 1 hour at −78° C., and then allowed to stir 18 hours at room temperature. The reaction was quenched with saturated aqueous ammonium chloride (20 mL), stirred 30 minutes at room temperature, diluted with water (50 mL) and extracted with ethyl acetate (2×50 mL). The organics were combined, dried over sodium sulfate, filtered and concentrated. The resultant residue was purified by flash chromatography (5-40% ethyl acetate/heptane, 25 g silica gel) to yield 256 mg of 1-tert-butyl 4-ethyl 4-((5-bromo-1-tert-butyl-1H-pyrazol-4-yl)methyl)piperidine-1,4-dicarboxylate as a clear oil. +ESI (M+H) 474.2, (M+2+H) 476.2; 1H NMR (400 MHz, CDCl3, δ): 7.20 (s, 1H), 4.16 (q, J=7.2 Hz, 2H), 3.93 (br. s., 2H), 2.84 (m, 2H), 2.66 (s, 2H), 2.10 (d, J=12.5 Hz, 2H), 1.72 (s, 9H), 1.45 (m, 11H), 1.25 (t, J=7.1 Hz, 3H).

Provenance & Evidence