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

Participants

Reaction Conditions

Reaction Steps

11 g of 7-bromo-3,4-dihydro-4,4-dimethyl-2H-1-benzothiopyran were dissolved in a mixture of 100 ml of ether and 10 ml of tetrahydrofuran and treated at -78° C. with 33 ml of a 1.6 molar solution of n-butyllithium in hexane. The reaction solution was held at -50° C. for 15 minutes, again cooled to -78° C. and gassed with carbon dioxide for 2 hours. Thereafter, the mixture was poured on to ice, acidified with 6N hydrochloric acid and extracted with ethyl acetate. The organic phases were washed with water, dried and evaporated. After recrystallization of the crude product from ethyl acetate/hexane, there were obtained 4.6 g of 3,4-dihydro-4,4-dimethyl-2H-1-benzothiopyran-7-carboxylic acid, melting point 202°-204° C.

Provenance & Evidence