1,4-Dioxane as a Sacrificial Radical Buffer Enables Pd-Catalyzed Regioselective C2 Acylation of Indolyl Ketoximes: Access to 2,3-Diacylindoles and Indole-Fused Heterocycles

Pd-catalyzed regioselective C2 acylation of indoles has been achieved using a C3-ketoxime directing group and glyoxal/aldehydes. The protocol provides C2 acylated indoles with high selectivity and enables one-pot access to indole-fused pyridazines and 2,3-diacylindoles. Mechanistic studies revealed that 1,4-dioxane acts not only as solvent but also as a sacrificial radical buffer that modulates TBHP derived tBuO• and tBuOO• species. Thereby suppressing undesired side reactions while facilitating the desired acylation pathway.