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

Participants

Reaction Conditions

Reaction Steps

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).

Provenance & Evidence