Reaction #1005975

Reaction equation

6-methoxy-2,2-dimethyl-thiochroman-4-one

BBr3

→

6-hydroxy-2,2-dimethylthiochroman-4-one

Yield 40.0%

Solvents

CH2Cl2

CH2Cl2

Conditions

Workup

1. 1
   Temperaturewas cooled to −78° C.
2. 2
   Otherquenched by the slow addition of 50 mL of H2O
3. 3
   TemperatureUpon warming to room temperature the aqueous layer
4. 4
   Extractionwas extracted with CH2Cl2
5. 5
   Washthe combined organic layers were washed with saturated aqueous NaHCO3, H2O, and saturated aqueous NaCl
6. 6
   Dryingbefore being dried over MgSO4
7. 7
   OtherRemoval of the solvents under reduced pressure
8. 8
   Othergave a green-brown solid which
9. 9
   Otherupon recrystallization (Et2O/hexanes)

Procedure

To a solution of 6-methoxy-2,2-dimethyl-thiochroman-4-one (6.0 g, 27 mmol) in 50 mL CH2Cl2 cooled to −23° C. was added BBr3 (20.0 g, 80.0 mmol; 80.0 mL of a 1M solution in CH2Cl2) over a 20 minute period. After stirring for 5 hours at −23° C. the solution was cooled to −78° C. and quenched by the slow addition of 50 mL of H2O. Upon warming to room temperature the aqueous layer was extracted with CH2Cl2 and the combined organic layers were washed with saturated aqueous NaHCO3, H2O, and saturated aqueous NaCl before being dried over MgSO4. Removal of the solvents under reduced pressure gave a green-brown solid which upon recrystallization (Et2O/hexanes) afforded 2.25 g (40%) of 6-hydroxy-2,2-dimethylthiochroman-4-one as a light brown solid. 1H NMR (300 MHz, CDCl3) δ: 7.63 (1H, d, J=2.8 Hz), 7.15 (1H, d, J=8.5 Hz), 7.01 (1H, dd, J=2.8, 8.5 Hz), 2.87 (2H, s), 1.46 (6H, s).

Source