Metal‐Free Hydrogenation of N‐Heterocycles with Trimethylamine Borane and TFA in Aqueous Solution

Abstract A metal‐free hydrogenation of quinoxalines and indoles with Me 3 N ⋅ BH 3 and TFA in water at room temperature is reported. The protocol is featured with the usage of environmentally friendly water as the solvent, no need of metal catalyst and broad substrate scope. Sensitive functional groups such as OH‐, NH 2 ‐, Cl‐, Br‐, especially ‐CN and ‐CO 2 Me were well tolerated. Preliminary mechanistic studies suggested that TFA and Me 3 N ⋅ BH 3 provided the proton and hydride sources for the product, respectively. magnified image