“On Water” Palladium Catalyzed Direct Arylation of 1<i>H</i>-Indazole and 1<i>H</i>-7-Azaindazole

Abstract

The C3 direct arylation of 1H-indazole and 1H-7-azaindazole has been a significant challenge due to the lack of the reactivity at this position. In this paper, we describe a mild and an efficient synthesis of new series of C3-aryled 1H-indazoles and C3-aryled 1H-7-azaindazoles via a C3 direct arylation using water as solvent. On water, PPh3 was effective as a ligand along with a lower charge of the catalyst Pd(OAc)2 (5 mol%) at 100 °C, leading to C3-aryled 1H-indazoles or C3-aryled 1H-7-azaindazoles in moderate to good yields.

Keywords

• indazole
• azaindazole
• arylation
• green chemistry
• C–H functionalization
• water