Hydrochloric Acid → 1,2-Dihydro-10-hydroxy-8-(3-methyl-2-octyl)-5-oxo-4H,5H-thiopyrano[3,4-c][1]benzopyran

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Reaction Steps

A solution of 6.4 g. (0.027 mole) of 5-(3-methyl-2-octyl-resorcinol of Example 1 and 5.0 g. (0.0266 mole) of ethyl 4-oxo-2,3,5,6-tetrahydro-4H-thiopyran-3-carboxylate [prepared according to the method of Bennett and Scorah, J. Chem. Soc., 194 (1927)] in 35 ml. of absolute ethanol was cooled in an ice bath while it was saturated with hydrogen chloride. The resulting deep red solution was tightly stoppered and allowed to stand at room temperature for 120 hours. After one day yellow crystalline material had collected on the bottom of the flask. The reaction mixture was warmed gently on the steam bath for 15 minutes, cooled and poured onto a water-ice mixture. The gum-like material that precipitated was extracted with several portions of chloroform. The chloroform solution was washed with aqueous potassium bicarbonate and with water and dried over sodium sulfate. Evaporation of the solvent left 7.5 g. of a light-colored solid. This material was triturated several times with boiling petroleum ether to remove unreacted keto ester. The residue was recrystallized from an ethyl acetate-petroleum ether mixture to give 6.5 g. (68%) of the desired compound, m.p. 153°-155°C.

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