Boron Trichloride → 5-hydroxy-7-methoxyspiro[2H-1-benzopyran-2,1'-cyclohexan]-4(3H)-one

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Reaction Steps

To a solution of 5,7-dimethoxy-spiro[2H-1-benzopyran-2,1'-cyclohexan]-4(3H)-one (prepared in Preparation 8) (0.70 g, 2.54 mmol) in dry dichloromethane (5 ml) is added dropwise 2M boron trichloride solution in dichloromethane (3 ml, 6 mmol) at -35° C. After one hour stirring at -30° to 0° C., ice-cold water is added to the mixture and the mixture is extracted with dichloromethane. The dichloromethane layer is washed with water, dried, and concentrated to yield 5-hydroxy-7-methoxyspiro[2H-1-benzopyran-2,1'-cyclohexan]-4(3H)-one as a crude crystalline solid (0.66 g, 99.5%). Recrystallization from hexane gives a product having a melting point of 69°-70° C.

Provenance & Evidence