A General One‐Pot Synthesis of 2 H ‐Indazoles Using an Organophosphorus–Silane System

A simple and direct approach for the regioselective construction of the privileged 2 H ‐indazole scaffold is described. The developed one‐pot strategy involves phospholene‐mediated N−N bond formation to access 2 H ‐indazoles. The amount of organophosphorus reagent was minimized by recycling the phospholene oxide with organosilane reductants. Starting from functionalized 2‐nitrobenzaldehydes and primary amines, a mild reductive cyclization, involving the use of commercially available phospholene oxide and silanes, delivered a wide variety of substituted 2 H ‐indazoles in good to excellent yields.