1H-Indazole-1-carboxylic acid, 3-forMyl-, 1,1-diMethylethyl ester

24424-99-5

5235-10-9

882188-88-7

General procedure for the synthesis of tert-butyl 3-formyl-1H-indazole-1-carboxylate from 3-formylindazole and di-tert-butyl dicarbonate: To an acetonitrile solution containing 3-formylindazole (1.0 eq.) and di-tert-butyl dicarbonate (1.2 eq.) was added DMAP (0.1 eq.). The reaction mixture was stirred at room temperature overnight. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in dichloromethane and washed with saturated sodium bicarbonate solution. The organic and aqueous phases were separated. The aqueous phase was extracted with dichloromethane. All organic phases were combined and washed sequentially with saturated ammonium chloride solution, water and brine. The organic phase was dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The resulting BOC-protected tert-butyl 3-formyl-1H-indazole-1-carboxylate can be used directly in the subsequent reaction without further purification.