反应详情

To a solution of 2-(difluoromethoxy)-3,6-dimethyl-5-nitropyridine (33.4 g, 153 mmol) in methylene chloride (100 mL) and ethanol (600 mL) was added 10% palladium on charcoal (3.3 g). The resulting suspension was hydrogenated on a Parr device at 40 psi H2 for 1 h. TLC was used to monitor the reaction. Additional 3.3 g of palladium on charcoal were added hourly until no starting material remained. A total of 13.2 g of Pd/C was added. The reaction mixture was kept under an H2 atmosphere for 2 h after the last addition of catalyst. The reaction mixture was filtered through Celite and sand and the collected solids were washed with ethyl acetate (2×100 mL). The filtrate was concentrated in vacuo to give a grey oil, which was purified by column chromatography on silica gel (35%→50% ethyl acetate in hexanes) to furnish 6-(difluoromethoxy)-2,5-dimethylpyridin-3-amine (25.7 g, 89% yield) as a pale yellow oil which solidified upon cooling in a refrigerator. The product was recrystallized from hexanes below 0° C. to afford white needles: mp 40-42° C.; 1H NMR (400 MHz, CDCl3) δ 7.35 (1, J=74.0 Hz, 1H), 6.84 (s, 1H), 2.27 (s, 3H), 2.15 (s, 3H); LRMS (ESI) m/e 189.2 [(M+H)+, calcd for Ca8H11N2OF2 189.1]. Anal calcd. for C8H10N2OF2: C, 51.12; H, 5.38; N, 14.86. Found: C, 51.17; H, 5.29; N, 14.87.

1. customthe reaction
2. waitThe reaction mixture was kept under an H2 atmosphere for 2 h
3. additionafter the last addition of catalyst
4. filtrationThe reaction mixture was filtered through Celite and sand
5. washthe collected solids were washed with ethyl acetate (2×100 mL)
6. concentrationThe filtrate was concentrated in vacuo
7. customto give a grey oil, which
8. customwas purified by column chromatography on silica gel (35%→50% ethyl acetate in hexanes)