4,5,6,7-Tetrafluoro-3-(trifluoromethyl)-1H-indazole synthesis

Yield:945038-89-1 43%

Reaction Conditions:

with hydrazine hydrate in toluene; for 72 h;Cooling with ice;Reflux;

Steps:

1 Step 1: 4,5,6,7-tetrafluoro-3-(trifluoromethyl)-1H-indazole

11.09 g (45.1 mmol) perfluoroacetophenone are dissolved in 100 mL toluene. The solution is cooled with a ice bath and 2.3 mL (2.37 g, 47,3 mmol, 1.05 eq) hydrazine-monohydrate is added dropwise. The mixture is heated to reflux for 3 days. After cooling to room temperatare,the mixture is washed two times with 100 mL saturated aqueous sodium hydrogen carbonate solution and two times with 100 mL water, dried over magnesium sulfate and the solvent is removed under reduced pressure. The yellow, oily residue is distilled from bulb tobulb at a temperature about 140 °C and pressure about 12 Pa. The crude product is dissolvedi hot hexane and the solution stored at -18 °C. The precipitated solid is filtered off and theslurry washed two times in 10 mL hexane. 5.0 g (43%) product are obtained as a slightly yellow solid.

References:

TW2018/43166,2018,A Location in patent:Paragraph 0087