反应详情

温度

-75 °C

6-Bromo-2-(3,4-dichlorophenyl)-3,4-dihydro-2H-pyrano[2,3-b]pyridine (1.5 g) was converted to the corresponding lithio intermediate according to the procedure described in Example 23 and then quenched at -90° C. with 1.3 ml of tri-n-butyl borate. The resulting dark solution was stirred at -75° C. for 2 hours and then allowed to warm to 0° C. The mixture was then acidified with 3N hydrochloric acid, the organic phase was separated, and the aqueous layer was extracted with ether. The combined organic layers were concentrated to give a light brown, tacky solid. To this material was added 25 ml of 30% hydrogen peroxide and the resulting mixture was warmed at 60° C. for 30 minutes. The mixture was then cooled and diluted with 75 ml of water and the resulting mixture was extracted with two 50-ml portions of methylene chloride. The methylene chloride extracts were combined, washed with aqueous saturated sodium chloride solution, dried over sodium sulfate and concentrated to give a yellow solid. Column chromatography (silica gel, 3% ethyl acetate/hexane) gave 2-(3,4-dichlorophenyl)-3,4-dihydro-6-hydroxy-2H-pyrano[2,3-b]pyridine melting at about 218°-219° C.

1. customquenched at -90° C. with 1.3 ml of tri-n-butyl borate
2. temperatureto warm to 0° C
3. customthe organic phase was separated
4. extractionthe aqueous layer was extracted with ether
5. concentrationThe combined organic layers were concentrated
6. customto give a light brown, tacky solid
7. temperaturethe resulting mixture was warmed at 60° C. for 30 minutes
8. temperatureThe mixture was then cooled
9. extractionthe resulting mixture was extracted with two 50-ml portions of methylene chloride
10. washwashed with aqueous saturated sodium chloride solution
11. dry with materialdried over sodium sulfate
12. concentrationconcentrated
13. customto give a yellow solid