1-Benzyl-4-piperidone → 1-Benzyl-4-[4-(trifluoromethyl)phenyl]-1,2,3,6-tetrahydropyridine

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Reaction Steps

4-Iodobenzo trifluoride (2.97 g, 10.92 mmol) in THF (50 mL) was added dropwise over 0.5 h to a solution of n-BuLi (7.5 ml, 1.6 M, 12 mmol) in THF (50 mL) at −78° C. The reaction mixture was stirred an additional 0.5 h upon which N-benzyl-4-piperidone (2.13 g, 11.69 mmol) in THF (10 mL) was added over 10 minutes. Stirring was continued for 0.5 h at −78° C., followed by room temperature overnight. The reaction was quenched with saturated ammonium chloride and the organic layer was separated. The aqueous layer was extracted with THF and the combined organic layers were dried (MgSO4), filtered and concentrated to afford a brown oil. The crude product was then dissolved in conc. HCl (30 mL) and 1,4-dioxane (6 mL) and stirred at 100° C. overnight. The reaction was poured into saturated sodium bicarbonate and extracted with ethyl acetate (3×200 mL). The combined organic layers were dried (MgSO4), filtered and concentrated. The product was purified by silica gel flash column chromatography (20% ethyl acetate in hexanes) to afford 1-benzyl-4-(4-trifluoromethyl-phenyl)-1,2,3,6-tetrahydro-pyridine (981 mg, 28%). 1H NMR (400 MHz, CDCl3) δ 7.61 (d, 2H), 7.52 (d, 2H), 7.40 (m, 5H), 6.21 (m, 1H), 3.70 (s, 2H), 3.25 (q, 2H), 2.78 (t, 2H), 2.62 (m, 2H); LCMS: 318.4 (M+1)+.

Provenance & Evidence