反应详情

温度

4 °C

To a magnetically stirred suspension of 3-hydroxy-4-nitro-benzoic acid (75 g, 0.41 mol) in 1,2-dichloroethane (1.5 L), under an argon blanket, was added trimethyl borate (69 g, 0.66 mol) and boron trifluoride diethyl etherate (94 g, 0.66 mol) at 20 □C. Borane-pyridine complex (57 g, 0.61 mol) was slowly added drop-wise over 2.5 hrs (exotherm to 44° C.). After addition was complete, the solution was stirred for 2.5 hrs then cooled in an ice bath to 4° C. Methanol (150 ml) was added over 15–20 min. to quench the reaction. The mixture was stirred for 45 min. while warming to 20 □C then concentrated in vacuo to a yellow solid residue. The solid was partitioned between 1N NaOH (450 ml) and toluene (600 ml). The phases were separated, and the organic portion was extracted with 1N NaOH (2×450 mL). The aqueous portions were combined and acidified to below pH 2 with the slow addition of conc. HCl (100 ml). The resulting thick suspension was extracted with ethyl acetate (750 ml, 500 nm). The combined organic extract was washed with water (2×450 mL), brine (450 mL), dried (MgSO4), filtered then concentrated in vacuo to give 62 g brownish yellow solid 1 (0.37 mol, 90%). An additional 106 g of intermediate 1 was obtained from three other reactions.

1. customover 2.5 hrs
2. custom(exotherm to 44° C.)
3. additionAfter addition
4. customto quench
5. customthe reaction
6. stirringThe mixture was stirred for 45 min.
7. temperaturewhile warming to 20 □C
8. concentrationthen concentrated in vacuo to a yellow solid residue
9. customThe solid was partitioned between 1N NaOH (450 ml) and toluene (600 ml)
10. customThe phases were separated
11. extractionthe organic portion was extracted with 1N NaOH (2×450 mL)
12. additionacidified to below pH 2 with the slow addition of conc. HCl (100 ml)
13. extractionThe resulting thick suspension was extracted with ethyl acetate (750 ml, 500 nm)
14. extractionThe combined organic extract
15. washwas washed with water (2×450 mL), brine (450 mL)
16. dry with materialdried (MgSO4)
17. filtrationfiltered
18. concentrationthen concentrated in vacuo