Transformation of alcohols to esters promoted by hydrogen bonds using oxygen as the oxidant under metal-free conditions

Abstract

Ionic liquid initiates and promotes oxidative esterification of alcohols to esters under metal-free conditions in oxygen.

Additive-Mediated Selective Oxidation of Alcohols to Esters via Synergistic Effect Using Single Cation Cobalt Catalyst Stabilized with Inorganic Ligand

“…Based on the experimental results and previous investigations [23,25,27], a plausible mechanism that underlies the catalysis cycle is depicted in Figure 4(c) 5 Research Figure 5 shows the 1 H NMR studies that were performed to follow the progress of the oxidative coupling of benzyl alcohol and methanol with and without KCl as an additive. To our delight, using KCl as an additive, the production of methyl benzoate (3.89 ppm) was detected after 3 h, and benzaldehyde as the only intermediate product was also observed (10.04 ppm).…”

“…Even unsaturated aromatic alcohols, such as cinnamyl alcohol, gave the targeted ester in excellent yields as well (compounds [21][22][23][24]. It is worth noted that reactivities of aliphatic alcohols are not comparable with benzylic alcohols, but they can also undergo aerobic oxidative esterification and give the ester products in moderate to good yields (compounds [25][26][27][28][29][30]. We also studied the preparation of active drug molecules via oxidation of alcohols, and all the substrates tested gave the corresponding drug molecules (compounds 31-34) in good yields of 82%-89%.…”

“…Heterogeneous catalysts can provide the benefits of easy separation from the reaction mixture, but the catalysts are not commercially available or otherwise are not easily accessible [22][23][24][25][26]. Very recently, in 2018, Gowrisankar and coworkers [27] reported an ionic liquid as catalyst for the oxidation of alcohols to esters, but the method required high pressures (10 or 20 bar) and lacked generality. Therefore, the development of promising catalytic systems towards direct conversion of alcohols to esters, which utilize robust and cheap base-metal catalysts under mild conditions in the presence of green oxidants, is highly desired.…”

Aerobic Oxidation in Ionic Liquids

“…Recently, a novel supported IL created by coating polystyrene-TEMPO resin with [bmim]PF 6 and CuCl 2 was introduced as an efficient catalyst with oxygen as an oxidant for the selective oxidation of activated alcohols. The supported IL contributed to the high catalytic activity and selectivity.…”

Aerobic Self‐Esterification of Alcohols Assisted by Mesoporous Manganese and Cobalt Oxide

“…They developed a Ru complex treated with base to get Ru II with electron rich ligands which would catalyze esterification. Homogeneous catalytic complexes, noble metal catalysts and photocatalytic systems, palladium assisted carbonylation, oxidative esterification, chemical oxidants, Au NPs, ozone, basic ionic liquids, and embedded graphite supported nanoparticles have demonstrated catalytic systems of direct esterification.…”