A kind of preparation method of linagliptin intermediate
A technology of intermediates and reaction time, which is applied in the field of preparation of linagliptin intermediates, can solve the problems of high reaction conditions and operation requirements, expensive starting materials, and low atom utilization, and achieve good industrialization prospects and product yields. High efficiency and purity, easy operation
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Embodiment 1
[0038] Embodiment 1: the preparation of formula II compound
[0039]
[0040] 2-Bromo-4-methylimidazole (1.610g, 10mmol), N-methylurea (0.889g, 12mmol), tert-butyl hydroperoxide (70%, 2.574g, 20mmol), and 20mL of acetonitrile were added to In a 100mL flask, heat the reaction system to 70°C, stir and react for 8 hours, cool to room temperature after the reaction, add 80mL ethyl acetate to dilute the reaction solution, wash once with saturated aqueous sodium chloride solution, then wash twice with water, and spin off under reduced pressure. Ethyl acetate gave crude product. The crude product was recrystallized from dichloromethane and cyclohexane to obtain 2.372 g of compound II with a yield of 96% and a purity of 99%. 1 HNMR (300MHz, CDCl 3) δ 13.00 (s, 1H), 12.27 (s, 1H), 8.19 (s, 1H), 7.87 (s, 1H), 2.75 (s, 3H). Mass spectrum (ESI): m / z = 246.9828 (M+H).
Embodiment 2
[0041] Embodiment 2: the preparation of compound II
[0042] 2-Bromo-4-methylimidazole (1.610g, 10mmol), N-methylurea (0.889g, 12mmol), tert-butyl peroxide (70%, 2.574g, 20mmol), 20mL of acetonitrile were added accordingly Put it into a 100mL flask, heat the reaction system to 90°C, stir and react for 8h, cool to room temperature after the reaction, add 80mL ethyl acetate to dilute the reaction solution, wash once with saturated aqueous sodium chloride solution, then wash twice with water, and spin evaporate under reduced pressure Ethyl acetate was removed to give the crude product. The crude product was recrystallized from dichloromethane and cyclohexane to obtain 2.223 g of compound II with a yield of 90% and a purity of 99%.
Embodiment 3
[0043] Embodiment 3: the preparation of compound II
[0044] 2-bromo-4-methylimidazole (1.610g, 10mmol), N-methylurea (1.111g, 15mmol), tert-butyl hydroperoxide (70%, 2.574g, 20mmol), 20mL dioxane Put it into a 100mL flask accordingly, heat the reaction system to 100°C, stir and react for 10h, cool to room temperature after the reaction, add 80mL of ethyl acetate to dilute the reaction solution, wash once with saturated aqueous sodium chloride solution, then wash twice with water, reduce Ethyl acetate was distilled off under pressure to obtain a crude product. The crude product was recrystallized from dichloromethane and cyclohexane to obtain 1.976 g of compound II with a yield of 80% and a purity of 99%.
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