1-(5-hydroxy-1H-indazol-1-yl)-Ethanone synthesis

Yield:-

Reaction Conditions:

with ammonium formate;palladium in acetone;

Steps:

17 1H-Indazoly-5-yl 3-fluorobenzenesulfonate

a suspension of 467 mg of 1-acetyl-5-benzyloxy-1H-indazole, 525 mg of ammonium formate, 1 g of 10% palladium-on-charcoal and 50 ml of acetone is brought to reflux for 3 hours. After returning to a temperature in the region of 20° C., the reaction medium is filtered through a bed of Celite 535. The filtrate is concentrated by evaporation under reduced pressure and the oil obtained is purified by chromatography on a silica column with a dichloromethane/methanol (98/2 by volume) mixture as eluent. 132 mg of 1-acetyl-5-hydroxy-1H-indazole are thus obtained in the form of a white solid (Rf=0.32, silica gel thin layer chromatography, eluent: methanol/dichloromethane (2/98 by volume)). 1-Acetyl-5-benzyloxy-1H-indazole can be obtained in the following way:

References:

US2004/106667,2004,A1