反应详情

To a solution of 1H-indazole-5-carbaldehyde (315.2 mg, 2.16 mmol), K2CO3 (598.8 mg, 4.33 mmol) in DMF (2.5 mL) was added dropwise a solution of I2 (938 mg, 3.7 mmol) in DMF (2.5 mL) and the reaction allowed to stir for three hours. An aqueous solution consisting of Na2S2O4 (511 mg)/K2CO3 (35 mg)/H2O (3.5 mL) was then added and the solution stirred for two hours. Water (30 mL) and aqueous sodium hydrogen sulfate (1M, 10 mL) was added and the product was extracted with ethyl acetate (350 mL); this organic layer was washed with brine (3×25 mL). The aqueous layer was then extracted with dichloromethane (3×75 mL), this second organic layer was also washed with brine (25 mL). TLC indicated product present in both, so the residues were combined and purified by chromatography (10 g silica SPE tube, Silicycle, 5% ethyl acetate in dichloromethane) to yield a beige solid (203 mg, 35%). A precipitate that formed in the original aqueous layer was collected by vacuum filtration to give after drying a beige solid (first crop 135.6 mg, 23%; second crop 147 mg, 25%). 1H NMR (400 MHz, CDCl3 plus a drop of CD3OD) δ 10.03 (s, 1H), 8.00 (s, 1H), 7.95 (d, J=8.8 Hz, 1H), 7.54 (d, J=8.8 Hz, 1H).

1. additionwas then added
2. stirringthe solution stirred for two hours
3. extractionthe product was extracted with ethyl acetate (350 mL)
4. washthis organic layer was washed with brine (3×25 mL)
5. extractionThe aqueous layer was then extracted with dichloromethane (3×75 mL)
6. washthis second organic layer was also washed with brine (25 mL)
7. custompurified by chromatography (10 g silica SPE tube, Silicycle, 5% ethyl acetate in dichloromethane)