反应详情

To a refluxing mixture of 7 (6.00 g, 16.4 mmol), CHCl3 (30 mL), EtOH (12 mL) and NH2OH.HCl (2.28 g, 32.9 mmol) was added dropwise a solution of pyridine (2.66 mL, 32.9 mmol) in CHCl3 (9 mL). When the addition was complete, a Soxhlet extractor containing MgSO4 was attached and the refluxing continued for 6 h. Selenium dioxide (2.73 g, 24.6 mmol) was then added portionwise over 1 h during reflux. Each time selenium dioxide was added an exothermic reaction occurred. When the addition was complete the reaction mixture was heated at reflux overnight. More SeO2 (1.00 g, 9.0 mmol) was added in one portion and the reflux continued for a further 1.5 h. The reaction mixture was cooled, sorbent (HM-N, Jones chromatography) added and the solvent evaporated. Purification by means of SGC using dichloromethane:hexane (1:1) (gradient elution) gave the product 8 (3.80 g, 64%) as a white solid; 1H NMR (400 MHz, CDCl3) δ 8.56 (d, J=2.2 Hz, 1H), 8.22 (m, 3H), 8.16 (d, J=2.1 Hz, 1H), 7.68 (tt, J=7.5, 1.2 Hz, 1H), 7.56 (t, 7.5 Hz, 2H).

1. additionWhen the addition
2. temperatureduring reflux
3. customan exothermic reaction
4. additionWhen the addition
5. temperaturewas heated
6. temperatureat reflux overnight
7. waitthe reflux continued for a further 1.5 h
8. temperatureThe reaction mixture was cooled
9. additionsorbent (HM-N, Jones chromatography) added
10. customthe solvent evaporated
11. customPurification by means of SGC