Hexane → t-Butyl 3-(4-fluorobenzylidene)-1-piperidinecarboxylate

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of (4-fluorophenylmethyl)triphenylphosphonium chloride (17.68 g, 43.5 mmol) in dry tetrahydrofuran (60 mL) at −78° C. was added 2.5 M n-butyllithium in hexane (14.6 mL, 36.5 mmol). The reaction was warmed to 0° C. for 1 hr. After tis time, t-butyl 3-oxo-1-piperidinecarboxylate (3.46 g, 17.4 mmol) in tetrahydrofuran (60 mL) was added. The mixture was stirred at room temperature for 1 hr and then heated to reflux for 16 hr. The reaction was cooled to room temperature and quenched by the addition of saturated aqueous ammonium chloride. The reaction was extracted with ethyl acetate three times (100 mL). The organic layers were combined, washed with brine, dried over magnesium sulfate, and evaporated in vacuo to a pale yellow oil. The oil was purified by flash chromatography (silica gel, hexane:ethyl acetate 9:1) to yield 3.82 g of a mixture of E and Z isomers as a colorless oil. 1H NMR (300 MHz, CDCl3) δ 7.22-7.14 (m, 2H), 7.04-6.98 (m, 2H), 6.36 (s, 0.33H), 6.28 (s, 0.67H), 4.14 (s, 1.34H), 4.00 (s, 0.66H) 3.50 (t, J=5, 2H), 2.47 (t, J=5, 0.66H), 2.39 (t, J=5, 1.34H), 1.75-1.68 (m, 1.34H), 1.65-1.57 (m, 0.66H), 1.48 (s, 9H).

Provenance & Evidence