反应详情

温度

90 °C

In a round bottom flask under a nitrogen atmosphere a mixture of N-(1-dimethylaminoethylidene)-5-ethyl-6-methoxy-2-methylnicotinamide (synthesized on 1.00 mmol scale), hydroxylamine hydrochloride (83.4 mg, 1.2 mmol), sodium hydroxide (48 mg, 1.2 mmol) and glacial acetic acid (1.4 mL) is treated with water (0.7 mL) and 1,4-dioxane (1 mL). The resulting dark mixture is stirred at 90° C. for 35 min. The reaction mixture is partitioned between water and ethyl acetate. The mixture is treated with excess solid sodium bicarbonate, the ethyl acetate layer is separated and the aqueous layer is extracted with 4 further portions of ethyl acetate. The combined ethyl acetate layer is dried over magnesium sulfate and evaporated to give a black residue that is purified by flash chromatography on a 5-gram silica gel cartridge by elution with dichloromethane. Fractions containing the product are combined, evaporated and re-purified by flash chromatography on a 5-gram silica gel cartridge by elution with heptane:dichloromethane (49:1). Fractions containing the product are combined and the solvent evaporated to give 3-ethyl-2-methoxy-6-methyl-5-(3-methyl-1,2,4-oxadiazol-5-yl)pyridine (189 mg, 81% yield, from Steps 1 and 2 above) as a white solid. MS: m/e=234 (M+H); 1H NMR (CDCl3, δ, ppm): 8.01 (1H, s), 4.01 (3H, s), 2.81 (3H, s), 2.60 (2H, q), 2.46 (3H, s), 1.23 (3H, t).

1. customThe reaction mixture is partitioned between water and ethyl acetate
2. additionThe mixture is treated with excess solid sodium bicarbonate
3. customthe ethyl acetate layer is separated
4. extractionthe aqueous layer is extracted with 4 further portions of ethyl acetate
5. dry with materialThe combined ethyl acetate layer is dried over magnesium sulfate
6. customevaporated
7. customto give a black residue that
8. customis purified by flash chromatography on a 5-gram silica gel cartridge by elution with dichloromethane
9. additionFractions containing the product
10. customevaporated
11. customre-purified by flash chromatography on a 5-gram silica gel cartridge by elution with heptane:dichloromethane (49:1)
12. additionFractions containing the product
13. customthe solvent evaporated