Water → 1H-Indazol-5-ol

Participants

Reaction Conditions

Reaction Steps

A solution of 5-methoxy-1H-indazole [0.410 g, Reference Example 24(a)] in dichloromethane (7.5 ml) was treated with a solution of boron tribromide in dichloromethane (7.5 ml, 1M). The mixture was then heated to reflux for 4 hours, then cooled to 0° C. and then treated dropwise with water (2 ml). The pH of this mixture was adjusted to 7-8 by addition of 10% aqueous sodium hydrogen carbonate. The mixture was then extracted three times with ethyl acetate. The combined extracts were dried over magnesium sulfate and then evaporated. The residual brown oil was subjected to flash column chromatography on silica eluting with a mixture of ethyl acetate and hexane (1:1, v/v) to give 5-hydroxy-1H-indazole (0.310 g) as a yellow solid. LC-MS (METHOD B): RT=1.96 minutes; 135 (M+H)+.

Provenance & Evidence