Hydrochloric Acid → 2,3-Dihydro-8-methoxy-4H-1-benzothiopyran-4-one

Participants

Reaction Conditions

Reaction Steps

8.64 g of phosphorous pentachloride was added to a solution of 8.0 g of 2-(2-methoxyphenylthio)ethanecarboxylic acid in 24 ml of benzene under the atmosphere of argon while cooling to 0° C. After stirring the reaction mixture for 20 minutes at 100° C., 9.13 ml of stannous tetrachloride was dropwise added to the mixture while cooling to -10° C. Following completion of dropping, the reaction mixture was warmed to 0° C. and stirred for 30 minutes. Next, 24 g of ice followed by 14 ml of concentrated hydrochloric acid were added followed by refluxing for about 30 minutes. After cooling the reaction mixture to room temperature, the organic layer was separated and the aqueous layer was extracted three times with benzene. After combining the organic layers and washing twice with water, the combined organic layer was dried over magnesium sulfate, the solvent was distilled off and the resulting crystal was recrystallized from ethyl acetate-hexane to obtain 5.53 g of the target compound 8-methoxythiochroman-4-one (yield: 76%, m.p.: 110°-110.5° C.).

Provenance & Evidence