Acetic Anhydride → (+/-)-4-((alphaR*)-3-acetoxy-alpha-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl)benzyl)-N,N-diethylbenzamide

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Reaction Steps

A solution of (±)-4-((αR*)-α-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl)-N,N-diethylbenzamide (1.2 g, 2.8 mmol, Example 6), acetic anhydride (0.40 mL, 4.2 mmol), and triethylamine (0.80 mL, 5.6 mmol) in 30 mL of dichloromethane was stirred overnight under nitrogen. The solution was washed twice with 15 mL of 5% sodium bicarbonate, dried over sodium sulfate and the solvent removed. The product was purified by chromatography on silica gel with ethyl acetate (30-100%) in dichloromethane to give 0.94 g (71%) of (±)-4-((αR*)-3-acetoxy-α-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl)benzyl)-N,N-diethylbenzamide as a white foam. NMR (200 MHz, DMSO-d6): δ 0.9 (d, J=6 Hz, 3H); 1.1 (d, J=6 Hz, 3H); 1.0-1.2 (br m, 6H); 1.75 (dd, J1 =7.5 Hz, J2 =12 Hz, 1H); 2.1 (dd, J1 =8.5 Hz, J2 =12.5 Hz, 1H); 2.2 (s, 3H); 2.4-2.6 (m, 3H); 2.7 (m, 1H); 2.8 (dd, J1 =7.5 Hz, J2 =15 Hz, 1H); 3.1 (dd, J1 =6 Hz, J2 =14 Hz, 1H); 3.1-3.4 (br m, 4H); 5.05 (d, J=15 Hz, 1H); 5.1 (s, 1H); 5.15 (d, 10 Hz, 1H), 5.8 (m, 1H) 7.0 (s, 1H); 7.0 (d, J=8 Hz, 1H); 7.15 (d, J=8 Hz, 1H); 7.25 and 7.4 (ABq, J=8 Hz; 4H); 7.4(t, J=8 Hz, 1H). The amine was dissolved in ethanol and converted to the monohydrochloride salt by titration with ethanolic hydrogen chloride. After the solvent was removed, the salt was dissolved in a minimal amount of dichloromethane and precipitated with diethyl ether. Filtration gave 0.50 g of the hygroscopic salt. Calc for C29H39N3O3HCl H2O: C, 65.46; H, 7.97; N, 7.90; Cl, 6.66. Found: C, 65.43; H, 7.97; N, 8.00; Cl, 6.79.

Provenance & Evidence