Oxidation is a fundamental and frequently used transformation in organic synthesis. Therefore, replacing the heavy metal-based catalysts which have been extensively used for a long time, is of great interest to develop efficient and environmentally benign organic synthesis.
Takayuki Yakura, University of Toyama, Japan, and colleagues have developed 2-iodo-N-isopropyl-5-methoxybenzamide as an efficient catalyst for the oxidation of primary and secondary alcohols. The reaction of benzylic and aliphatic alcohols with a catalytic amount of the catalyst in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as a co-oxidant and Bu4NHSO4 at room temperature gave good to excellent yields of the corresponding carbonyl compounds.
The team had evaluated several N-isopropyliodobenzamides as catalysts for the oxidation of benzhydrol to benzophenone. A study on the substituent effect of the benzene ring on the oxidation showed that its reactivity increased in the following order of substitution: 5-NO2 < 5-CO2Me, 3-OMe < 5-OAc < 5-Cl < H, 4-OMe < 5-Me < 5-OMe. The high reactivity of the 5-methoxy derivative at room temperature is a result of the rapid generation of the pentavalent species from the trivalent species during the oxidation.
According to the researchers, 5-methoxy-2-iodobenzamide is an efficient and environmentally benign catalyst for the oxidation of alcohols, especially benzylic alcohols.
- 2-Iodo-N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation,
Takayuki Yakura, Tomoya Fujiwara, Akihiro Yamada, Hisanori Nambu,
Beilstein J. Org. Chem. 2018, 14, 971–978.
This article is part of the Thematic Series Hypervalent iodine chemistry in organic synthesis. Guest Editor is Thomas Wirth, Cardiff University, UK