p-Toluenesulfonic acid → 2-(2-Tetrahydrothienyl)-3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one

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Reaction Steps

A mixture of 7 parts of dimedone, 7 parts of 2,3-dihydrothiophene, 150 parts by volume of benzene and 0.7 parts of p-toluenesulfonic acid was refluxed by heating while stirring for 1 hour and 30 minutes and then allowed to stand at room temperature for 12 hours. The reaction mixture was washed with 50 parts by volume of water and then treated three times with 50 parts by volume of a 10% aqueous solution of sodium hydroxide. The aqueous layer was collected and the pH was adjusted to 2.0 with the addition of 6 N hydrochloric acid while maintaining the temperature thereof below 10° C. The light yellow colored crystals thus deposited were collected and purified by passing through a column containing a silica gel using a solvent mixture of chloroform and benzene (1:1) as a spreading agent to obtain 2-(2-tetrahydrothienyl)-3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one in a form of colorless fine crystals. The melting point was 97° to 99° C. The yield was 8 parts.

Provenance & Evidence