Water → 1-(1-Benzylpiperidin-4-yl)-3-phenyl-1-propanone

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Reaction Steps

To a solution of 1.115 g 4-(3-phenylpropylidene)-1-benzylpiperidine from Step B in 40 mL anhydrous ether under nitrogen was added 11.5 mL 1M borane solution in THF with stirring. After stirring for three hours, 2 mL of water was added dropwise, and the mixture was stirred for 30 min. After cooling with ice, a solution prepared from 0.287 g chromic anhydride, 0.624 mL concentrated sulfuric acid and 15 mL water was added dropwise with vigorous magnetic stirring over 5 minutes. After stirring for an additional 5 minutes, the cooling bath was removed. After 1.5 hours more, 100 mL each of 0.5N NaOH & ether was added, and the mixture was stirred to disolve a solid residue. After separating the layers, the aqueous layer was extracted with 2×100 mL ether. The combined ether layer was washed with 100 mL each of EDTA, water, and saturated brine, dried over Na2SO4, and concentrated under reduced pressure to give a colorless gel. The oxidation step were then repeated with half of the reagent used above. Flash chromatography on silica gel with 30˜50% EtOAc in hexanes with 3% (v/v) Et3N gave 0.293 g of the title compound as a colorless gel. RF: 0.41 (30% EtOAc in hexanes having 3% (v/v) Et3N). 1H NMR (500 MHz, CDCl3): δ7.17˜7.33 (m, ˜10H), 3.51 (s, 2H), 2.88˜2.92 (m, 2H), 2.75˜2.80 (m, 2H), 2.26˜2.32 (m, 1H), 1.98˜2.04 (m, 2H), 1.76˜1.82 (m, 2H), 1.63˜1.72 (m, 4H). ESI-MS 308.1 (M+H), HPLC A: 2.45 min.

Provenance & Evidence