Reaction Steps
A 25-mL, three-necked, round-bottomed flask was equipped with a magnetic stirrer, a standard condenser with a N2 inlet, a 10-mL addition funnel, and two glass stoppers. To a mixture of the amine (31, 0.60 g, 3.57 mmol) in CH2Cl2 (5 mL) and 10% NaOH (3.58 g, 8.93 mmol) was added dropwise a solution of 3,4-dimethoxybenzoyl chloride (0.80 g, 3.92 mmol) in CH2Cl2 (10 mL) over 15 min. Stirring of the mixture was continued for an additional 3 h under N2. An aqueous mixture, formed upon addition of H2O (30 mL), was extracted (CH2Cl2, 4×25 mL). Combined extracts were dried (Na2SO4, 2 h), filtered and concentrated to give a viscous yellow oil. Chromatography of the oil was performed on neutral alumina (74 g, 1.7 cm×32 cm) using 60:40 ethyl acetate/hexanes as eluant. Fractions (Rf = 0.31) were saved and concentrated (rotary evaporator then vacuum pump, overnight, RT/0.2 mm Hg) to give 0.87 g (73.1%) of off-white solid (34); mp 67.5°-69.5° C. IR (KBr) cm-1 3055 (Ar C--H), 2950, 2915, 2845, 2820, 2770, 2750, 2710 (C--H), 1625 (C=O); 1H NMR (DCCl3) δ0.96 (d, 3 H, CH3, J=6.4 Hz), 1.06 (d, 3 H, CH3, J=6.5 Hz), 1.62-1.75 [m, 3 H, H(5) and H(9)], 1.96 [bs, 1 H, H(1)], 2.43 [bd, 1 H, H(4)ax, J=9.7 Hz], 2.51 [bd, 1 H, H(6)ax, J=10.5 Hz], 2.62 [heptet, 1 H, CH(CH3)2, J=6.4 Hz], 2.74 [bd, 1 H, H(6)eq, J=9.9 Hz], 3.00-3.09 [m, 2 H, H(4)eq and H(2)ax ], 3.32 [bd, 1 H, H(8)ax, J=13.2 Hz], 3.83-3.94 [m, 7 H, H(8)eq and OCH3 ], 4.77 [bd, 1 H, H(2)eq, J=13.3 Hz], 6.84-6.94 (m, 3 H, Ar--H); 13C NMR (DCCl3) ppm 16.46, 19.15 (CH3), 29.13 [C(1)], 29.86 [C(5)], 32.36 [C(9)], 46.71 [C(2)], 52.25 [C(4)], 52.65 [C(8)], 54.35 [CH(CH3)2 ], 54.68 [C(6)], 55.88, 55.93 (OCH3), 110.50, 119.64, 130.23, 148.78, 149.39 (Ar--C), 169.90 (C=O). Anal. Calcd. for C19H28N2O3 : C, 68.65; H, 8.49. Found: C, 68.58; H, 8.47.
