[Synthesis]
General procedure for the synthesis of (R)-(-)-2-methylpiperazine L-tartrate from (R)-2-methylpiperazine L-tartrate: (R)-2-methylpiperazine L-tartrate (from Example 4) was dissolved in water (182 L) and branched octane (200 L), added to a 4,000 L reactor and stirred until completely dissolved. Subsequently, more branched octane (530 L) was added to the reactor and a 50% sodium hydroxide solution (1120 kg) was slowly added over a temperature range of 35°C to 52°C. The reaction mixture was heated to 80 °C with continuous stirring for 2 h. The lower aqueous phase was then separated and transferred to a 4000 L receiver. The organic phase in the reactor was cooled to 21°C, filtered through a 48-inch Nutsche filter, and the filtrate was transferred to a 1200L reactor. The 4000L reactor and filter were rinsed with branched octane (300L). The solid product was dried over nitrogen at 25 °C to give a final 24.9 kg (67% yield) of (R)-(-)-2-methylpiperazine with an optical purity of not less than 99% ee (as determined by chiral HPLC). The pH of the aqueous phase in the receiver was adjusted to 8.4 with acetic acid (812 kg) prior to treatment.The overall yield of (R)-(-)-2-methylpiperazine was 42% starting from (R)-2-methylpiperazine L-tartrate. The melting point of the product was 91-93 °C.1H NMR (400 MHz, CDCl3) δ: 2.97-2.68 (6H, m), 2.35 (1H, dd, J = 11.7, 10.2 Hz), 1.61 (2H, s), 1.00 (3H, d, J = 6.7 Hz), 0.00 (TMS, ref).13C NMR ( 100MHz, CDCl3) δ: 54.14(t), 51.89(d), 47.43(t), 46.46(t), 20.08(q), 0.00 (TMS, ref.) IR (mineral oil paste) νmax: 3220(s, br), 2819(s), 2748, 2042(w), 1995(w), 1981(w), 1328, 1328(s, d, J = 6.7Hz), 0.00 (TMS, ref.). (w), 1328, 1279, 1137, 1094, 960, 859(s), 845(s), 795(s), 621(s) cm-1. HRMS (FAB) calculated value for C5H12N2 [M+H]+: 101.1079, measured value: 101.1080. [α]25D = -17° (c 0.85, CH2Cl2). Elemental analysis calculated values for C5H12N2: C, 59.96; H, 12.07; N, 27.97. measured values: C, 59.25; H, 11.71; N, 27.64. |