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

doi:10.3762/bjoc.14.82

2-Iodo- N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation

Beilstein J Org Chem. 2018 Apr 30:14:971-978. doi: 10.3762/bjoc.14.82. eCollection 2018.

Authors

Takayuki Yakura¹, Tomoya Fujiwara¹, Akihiro Yamada¹, Hisanori Nambu¹

Affiliation

¹ Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani, Toyama 930-0194, Japan.

Abstract

Several N-isopropyliodobenzamides were evaluated as catalysts for the oxidation of benzhydrol to benzophenone in the presence of Oxone^® (2KHSO₅·KHSO₄·K₂SO₄) as a co-oxidant at room temperature. A study on the substituent effect of the benzene ring of N-isopropyl-2-iodobenzamide on the oxidation revealed 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 oxidation of various benzylic and aliphatic alcohols using a catalytic amount of the most reactive 5-methoxy derivative successfully resulted in moderate to excellent yields of the corresponding carbonyl compounds. 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 reaction. 5-Methoxy-2-iodobenzamide would be an efficient and environmentally benign catalyst for the oxidation of alcohols, especially benzylic alcohols.

Keywords: hypervalent iodine; iodobenzamide; organic catalysis; oxidation; oxone.