Hydrochloric Acid → 2-o-Tolyl-chroman-6-ol

Temperature

0 °C

To a solution of 6-bromo-2-o-tolyl-chroman (1 g, 3.3 mmol) in tetrahydrofuran (3 ml) at −78° C. n-butyllithium (2.2 M in cyclohexan, 1.8 ml, 1.2 eq) was slowly added and the mixture kept at −78° C. for 30 min. Triisopropyl borate (1.9 g, 2.3 ml, 9.9 mmol, 3 eq) was added and stirring was continued at the same temperature for 1 h. The cold solution was poured in a solution of ethanol (1.1 ml), water (3.0 ml) and aqueous sodium hydroxide (8 M, 1.6 ml). To this solution hydrogen peroxide (aqueous 35%, 0.9 ml, 3.1 eq) was slowly added while the temperature was kept <30° C. Stirring at room temperature was continued for 15 min, the suspension was cooled to 0° C. and adjusted to pH<7 using aqueous hydrochloric acid. To the resulting solution a saturated aqueous solution of sodium sulfite (4 ml) was added and the aqueous layer extracted with ethyl acetate. The combined organic layers were dried with sodium sulfate and filtered, and the solvent removed under reduced pressure. The crude product was purified by column chromatography (silica gel; ethyl acetate/heptane gradient). 2-o-Tolyl-chroman-6-ol was obtained as a pale yellow solid (480 mg, 60%).

1. waitwas continued at the same temperature for 1 h
2. customwas kept <30° C
3. stirringStirring at room temperature
4. waitwas continued for 15 min
5. extractionthe aqueous layer extracted with ethyl acetate
6. dry with materialThe combined organic layers were dried with sodium sulfate
7. filtrationfiltered
8. customthe solvent removed under reduced pressure
9. customThe crude product was purified by column chromatography (silica gel; ethyl acetate/heptane gradient)

ORD record

ord-1817531790204155b459d3d76d2398a0

Source dataset

uspto-grants-2014_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08912224B2