反应详情

A 1-L flask was charged with diethoxyacetonitrile (25.0 g, 0.19 mol), a solution of sodium methoxide in methanol (4.32 g of 25 wt % solution, 0.02 mol, 10 mol %), and methanol (200 mL). The mixture was stirred at room temperature for 20 h, affording a solution of the imidate ester, 2,2-diethoxy-acetimidic acid methyl ester. The reaction mixture was treated with the amidrazone, N′-methylpyrazine-2-carbohydrazonamide (28.7 g, 0.19 mol, 1 equiv), from Step 1, and acetic acid (18.0 g, 0.30 mol, 1.5 equiv). The mixture was stirred at room temperature for 3 h, upon which time the reaction was complete by LC/MS. The volatiles were removed in vacuo, affording a viscous oil. This was basified with 20% Na2CO3 (100 mL) and saturated NaHCO3 (200 mL), and extracted several times with ether (2 L total). The ether phase was washed with water (1×200 mL), dried over Na2SO4, filtered, and evaporated, affording the title acetal as a yellow oil (44.6 g, 89%). 1H NMR (300 MHz, CDCl3): δ 1.24 (t, J=6 Hz, 6H), 3.62 (5-line pattern, J=6 Hz, 2H), 3.79 (5-line pattern, J=6 Hz, 2H), 4.08 (s, 3H), 5.68 (s, 1H), 8.56 (m, 1H), 8.63 (m, 1H), 9.34 (s, 1H). MS (APCI) calcd for C12H17N5O2: 263.14, found (M+H+): 264.1