Hydrochloric Acid → 8-Benzyl-8-azabicyclo(3.2.1)octan-3-one

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Concentrated hydrochloric acid (30 mL) was added to a heterogeneous solution of 2,5-dimethoxy tetrahydrofuran (82.2 g, 0.622 mol) in water (170 mL) while stirring. In a separate flask cooled to 0° C. (ice bath), concentrated hydrochloric acid (92 mL) was added slowly to a solution of benzyl amine (100 g, 0.933 mol) in water (350 mL). The 2,5-dimethoxytetrahydrofuran solution was stirred for approximately 20 min, diluted with water (250 mL), and then the benzyl amine solution was added, followed by the addition of a solution of 1,3-acetonedicarboxylic acid (100 g, 0.684 mol) in water (400 mL) and then the addition of sodium hydrogen phosphate (44 g, 0.31 mol) in water (200 mL). The pH was adjusted from pH 1 to pH˜4.5 using 40% NaOH. The resulting cloudy and pale yellow solution was stirred overnight. The solution was then acidified to pH 3 from pH 7.5 using 50% hydrochloric acid, heated to 85° C. and stirred for 2 hours. The solution was cooled to room temperature, basified to pH 12 using 40% NaOH, and extracted with DCM (3×500 mL). The combined organic layers were washed with brine, dried (MgSO4), filtered and concentrated under reduced pressure to afford the title intermediate in quantitative yield as a viscous brown oil (˜95% purity based on analytical HPLC). 1H-NMR (CDCl3) δ (ppm) 7.5-7.2 (m, 5H, C6H5), 3.7 (s, 2H, CH2Ph), 3.45 (broad s, 2H, CH-NBn), 2.7-2.6 (dd, 2H, CH2CO), 2.2-2.1 (dd, 2H, CH2CO), 2.1-2.0 (m, 2H, CH2CH2), 1.6 (mn, 2H, CH2CH2). (m/z): [M+H]+ calcd for C14H17NO 216.14; found, 216.0.

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