Hydrogen peroxide based oxidation of hydrazines using HBr catalyst
作者:Jian Wang、Zichao Ma、Wanting Du、Liming Shao
DOI:10.1016/j.tet.2021.132546
日期:2021.12
Azo compounds (RN = NR′) are an important class of organic molecules that find wide application in organic synthesis. Herein, we report an efficient, practical and metal-free oxidation of hydrazines (RNH-NHR’) to azo compounds using 5 mol% HBr and hydrogen peroxide as terminal oxidant. This new method has been demonstrated by 40 examples with excellent yields. In addition, we showcased two examples
hydrazoarenes using ethanol as a hydrogen source by a bidentate Ru(II)-NC complex is developed. A weak base is crucial for this semihydrogenation that can efficiently avoid hydrazoarene dehydrogenation under strongly basic conditions. Control experiments and density functional theory calculations demonstrate the mechanism via a Meerwein–Ponndorf–Verley mechanism, and the only byproduct is ethylacetate. This study
Cobalt-catalyzed borylative reduction of azobenzenes using pinacolborane is developed. The simple cobalt chloride catalyst and reaction conditions make this protocol attractive for hydrazobenzene synthesis. This borylative reduction shows good functional group compatibility and can be readily scaled up to the gram scale. Preliminary mechanistic studies clarified the proton source of the hydrazine products