CC(C)([O-])C.[K+].[OH:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][C:9]=1[C:14](=[O:16])[CH3:15].[C:17](=S)=[S:18].O>C1C=CC=CC=1>[SH:18][C:17]1[O:7][C:8]2[CH:13]=[CH:12][CH:11]=[CH:10][C:9]=2[C:14](=[O:16])[CH:15]=1Part A: Potassium t-butoxide (134 g, 1.2 mole) is covered with benzene (1 L) in a flame dried round bottom flask equipped with an overhead stirrer, addition funnel, thermometer, and a nitrogen inlet. This suspension is maintained at 15° C. A solution of o-hydroxyacetophenone (54.4 g, 48.1 ml, 0.4 mole) and carbon disulfide (30.4, 24 ml, 0.4 mole) in benzene (700 ml) is slowly added over 1.3 hours, applying an ice bath periodically in order to maintain the temperature 18° C. The slurry which forms is stirred at ambient temperature for one day. The reaction mixture is transferred to a separatory funnel containing water (4 L) and extracted with ether (4×250 ml) and EtOAc (3×250 ml). The aqueous layer is acidified with 10% H2SO4 (1 L) and stirred at ambient temperature overnight. The resulting solid is filtered off and dried in vacuo at 50° C. overnight to yield 22.07 g of 2-mercapto-4H-1-benzopyran-4-one. Mp 207°-8° C.
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