Methoxyacetic Acid → N-benzyl-2-methoxy-N-(2-methylcyclopropyl)methylethanamine

Beteiligte Stoffe

Reaktionsschritte

Coupling In a 500 mL flask methoxyacetic acid (2.24 g, 24.8 mmol), N-benzyl-1-(2-trans-methylcyclopropyl)methanamine hydrochloride (5.0 g, 23.6 mmol) and DIPEA (13.4 g, 104 mmol) were dissolved in 300 mL of dichloromethane. To this solution at rt BOP (11.0 g, 24.8 mmol) was added as a solid portionwise and stirred 15 minutes. The reaction mixture was evaporated ini vacuo. Purification by flash chromatography (25-35% ethyl acetate:hexanes) provided a mixture of cis and trans amides as a clear oil: ES MS (M+H)=248.1. Step B: Reduction A 500 mL flask charged with N-benzyl-2-methoxy-N-(2-methoxycyclopropyl)methyl acetamide (from step A, 7.75 g, 31.3 mmol) in THF (100 mL) was added BH3-THF (1.0 M, 94 mL, 94 mmol) dropwise via an addition funnel. Upon complete addition (10 min.) the mixture was refluxed for 14 h. The mixture was allowed to cool to rt and quenched carefully with MeOH (15 mL). The mixture was then treated with 15 mL concentrated HCl and heated to reflux for 5 h. The reaction was evaporated in vacuo and partitioned between ethyl acetate and 20% NaOH solution. The aqueous layer was washed with ethyl acetate (3×). The combined organics were dried over sodium sulfate, filtered and evaporated in vacuo. Purification by reverse phase LC gave N-benzyl-2-methoxy-N-(2-methylcyclopropyl)methylethanamine as a clear oil: 1H NMR (400 MHz, CDCl3) δ 7.28 (m, 5H), 3.70 (bq, J=13.5 Hz, 2H), 3.49 (bs, 2H), 3.31 (s, 3H), 2.75 (bm, 2H), 2.51 (m, 1H), 2.31 (m, 1H), 1.03 (d, J=5.86, 3H), 0.59 (m, 1H), 0.48 (m, 1H), 0.22 (m, 2H). ES MS (M+H)=234.2. Step C: Hydrogenation A degassed solution of N-benzyl-2-methoxy-N-(2-methylcyclopropyl)methylethanamine (4.89 g, 20.9 mmol) in 150 mL ethyl alcohol was treated with palladium hydroxide (20% on carbon, 0.29 g) and hydrogen chloride (5.24 mL of a 4M solution in dioxane, 21 mmol) then placed under a hydrogen atmosphere for 16 hours. The reaction mixture was degassed with nitrogen, filtered through celite, washed with methanol and evaporated in vacuo to give (2-methoxyethyl)[(2-methylcyclopropyl)methyl]amine hydrochloride as a pale yellow oil: 1H NMR (400 MHz, CD3OD) δ 3.65 (m, 2H), 3.41 (s, 3H), 3.21 (m, 2H), 2.92 (m, 2H), 1.09 (d, J=5.68 Hz, 3H), 0.80 (m, 2H), 0.57 (m, 1H), 0.46 (m, 1H).

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