Carbon Dioxide → 4,4-Dimethyl-7-carboxythiochroman

Temperature

-78 °C

To a stirred solution of 1.0 g (3.9 mmol) of the 4,4-dimethyl-7-bromothiochroman and 4,4-dimethyl-5-bromothiochroman mixture in 12 ml of anhydrous ether at -78° C. was added, dropwise under nitrogen, 6.0 ml of 1.7 M 10.2 mmol) tert-butyllithium in pentane. The reaction mixture was stirred at -78° C. for 1 hour and then a rapid stream of dry carbon dioxide gas was passed through it with vigorous stirring. The reaction mixture was warmed to -20° C. and then quenched with water. The mixture was warmed to room temperature and its pH adjusted to 10 with ammonium hydroxide. The basic solution was washed with 2×10 ml ether and then acidified with dilute HCl. The mixture was extracted with 3×20 ml of ether. The ether extracts were combined and washed with water and saturated NaCl solution and then dried (MgSO4). The ether solution was filtered and the solvent removed in-vacuo. The residue was recrystallized from a mixture of ethyl acetate and hexane to give the captioned compound as a white solid. PMR (CDCl3): δ1.33 (6H, s), 1.96 (2H, s), 3.04 (2H, m), 7.42 (1H, d, J~8.1 Hz), 7.66 (1H, dd, J~8.1 Hz, 1.8 Hz), 7.77 (1H, d, J~1.8 Hz).

1. temperatureThe reaction mixture was warmed to -20° C.
2. customquenched with water
3. temperatureThe mixture was warmed to room temperature
4. washThe basic solution was washed with 2×10 ml ether
5. extractionThe mixture was extracted with 3×20 ml of ether
6. washwashed with water and saturated NaCl solution
7. dry with materialdried (MgSO4)
8. filtrationThe ether solution was filtered
9. customthe solvent removed in-vacuo
10. customThe residue was recrystallized from a mixture of ethyl acetate and hexane

ORD record

ord-576883f4d1c54555a2f8dd9ef9534558

Source dataset

uspto-grants-1990_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04895868