Intermolecular Gold-Catalyzed Nitrene Transfer Employing Aryl Azides: An Access to 7-Functionalized 2-Aminoindoles

Abstract

We report on intermolecular gold-catalyzed nitrene transfer, utilizing o-functionalized aryl azides as nitrene transfer reagents. This catalytic reaction provides a modular route to 7-functionalized 2-aminoindoles. Due to the optimized reaction conditions (toluene, 80–100 °C), a variety of functional substituents proved compatible (36 examples; yields up to 98%). The reaction can be performed using both homogeneous and heterogeneous catalytic variants with a low catalyst loading (1 mol %). The synthetic potential of the obtained products was illustrated by post-modifications of the indole backbone and peripheral substituents. A plausible reaction mechanism includes the generation of intermediate α-imino carbenes directly from the o-functionalized aryl azides or other nitrene sources, such as anthranils or benzofuroxans, which form during the reaction in the cases of the specific aryls.