反应详情

To a solution of carboxylic acid 16 (110 mg, 0.40 mmol) in anhydrous THF (5 mL) was added 1,1′-carbonyldiimidazole (77 mg, 0.439 mmol) at rt, and the mixture was stirred overnight. To this solution was added t-butyldimethylsilylhydroxylamine (200 mg, 1.36 mmol). The mixture was stirred at rt for 14 h and then at 45° C. for 3 h. The resulting yellow solution was diluted with water (5 mL), stirred for 20 minutes, and then extracted with ethyl acetate (3×15 mL), dried, and concentrated. Purification by flash silica gel chromatography (80% ethyl acetate in hexanes and then ethyl acetate only) afforded the title compound 17 (44 mg, 38% yield): 1H NMR (300 MHz, CDCl3) δ 7.18 (dd, J=15.0, 10.2 Hz, 1H), 7.13 (d, J=8.7 Hz, 1H), 6.71 (d, J=8.7 Hz, 2H), 5.96-6.17 (m, 2H), 5.66 (br d, J=15.0 Hz, 1H), 4.09 (dd, J=7.5, 5.7 Hz, 1H), 3.17(s, 3H ), 2.94 (s, 6H), 2.61 (m, 1H),2.43 (m, 1H); 13C NMR (75.4 MHz, CDCl3) δ 40.6, 41.5, 56.2, 82.9, 112.4, 117.4, 127.6, 128.7, 130.1, 139.9, 141.9, 150.3, 165.5.

1. stirringThe mixture was stirred at rt for 14 h
2. waitat 45° C. for 3 h
3. stirringstirred for 20 minutes
4. extractionextracted with ethyl acetate (3×15 mL)
5. customdried
6. concentrationconcentrated
7. customPurification by flash silica gel chromatography (80% ethyl acetate in hexanes