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

Abstract

<jats:p>The direct catalytic oxidation of alcohols to esters is very appealing, but the economical-friendly catalysis systems are not yet well established. Herein, we show that a pure inorganic ligand-supported single-atomic cobalt compound, (NH<jats:sub>4</jats:sub>)<jats:sub>3</jats:sub>[CoMo<jats:sub>6</jats:sub>O<jats:sub>18</jats:sub>(OH)<jats:sub>6</jats:sub>] (simplified as CoMo<jats:sub>6</jats:sub>), could be used as a heterogeneous catalyst and effectively promote this type of reaction in the presence of 30% H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> using KCl as an additive. The oxidative cross-esterification of various alcohols (aromatic and aliphatic) could be achieved under mild conditions in nearly all cases, affording the corresponding esters in high yields, including several drug molecules and natural products. Detailed studies have revealed that chloride ion is able to bind to the CoMo<jats:sub>6</jats:sub> to form a supramolecular dimer 2(CoMo<jats:sub>6</jats:sub>∙Cl), which can effectively catalyze the reaction <jats:italic>via</jats:italic> a synergistic effect from chloride ion and CoMo<jats:sub>6</jats:sub>. Mechanism studies and control reactions demonstrate that the esterification proceeds <jats:italic>via</jats:italic> the key oxidative immediate of aldehydes.</jats:p>

Selective iron-catalyzed aerobic oxidation of alcohols in water to carboxylic acids mediated by additives

“…1, the chloride ion can bind with FeMo 6 through multiple hydrogen bonds to drive the formation of a supramolecular compound (FeMo 6 ·Cl), just as the adduct of bromide ion does with FeMo 6 and the chloride ion does with CoMo 6 , as we have previously reported. 15 In the supramolecular compound, three relatively strong hydrogen bonds were formed by coordinating three protonated μ3-oxo ligands (O1, O2 and O3) on the same side of FeMo 6 with chloride ions, which could be suggested by the short donor–acceptor distances (typically, O–H⋯Cl = 3.171 Å). The electrostatic repulsion between the anionic (FeMo 6 ) catalyst and the chloride ion could be overcome by relying on the accumulation of multiple hydrogen bonds.…”

Morphologically controlled synthesis, characterization, and applications of molybdenum oxide (MoO3) nanoparticles

“…[29] Moreover, molecular molybdenum oxides are being studied extensively in literature. [30][31][32][33][34][35]…”

Infinite building blocks for directed self-assembly of a supramolecular polyoxometalate–cyclodextrin framework for multifunctional oxidative catalysis

“…The intelligent integration of catalytically active POMs and toroidal CDs into supramolecular assemblies has made them excellent catalysts towards organic transformations. [36][37][38][39] However, one drawback arises from the high solubility of POMs in water, which causes the deconstruction of the complexes in aqueous media or when using aqueous agents such as H 2 O 2 . 36 To solidify the POM-CD complexes, cross-linking of CDs has been proved to be highly efficient in the construction of POM-CD nanowires, functional 2D membranes and porous frameworks for sieving molecules/nano-objects and sensing pollutants.…”