Solvent-free oxidation of cumene by molecular oxygen catalyzed by cobalt salen-type complexes

Abstract

Co(salen)-type [where salen = di-(salicylal)-ethylenediimine] complexes were shown to be efficient catalysts in the oxidation of 2-phenylpropane (cumene) by dioxygen primarily to 2-phenyl-2-propanol (cumyl alcohol), 2-phenylpropene (a-methylstyrene), and 1-phenylethanone (acetophenone) applying 1 H NMR spectroscopy and gas chromatography-mass spectrometry (GC-MS). The effect of substitution on the ligand was also monitored in both oxygen-absorption and the catalytic reaction. Based on these results, the trend observed for the production of a-methylstyrene and cumyl alcohol were parallel to dioxygen uptake by the catalyst in neat cumene, while acetophenone productions obeyed a non-linear trend. The best selectivity for the reaction in terms of acetophenone production was observed for the complex with the least oxygen-absorption feature. The intermediate of the reaction, LCo(III)-OOcumyl (where L = salen) complex, was synthesized and characterized by IR, 1 H NMR spectroscopy as well as elemental analysis, and its reactivity in the present catalytic reaction was also studied. A series of experiments were performed to propose a mechanism for the reaction on the basis of the product distributions in the reaction mixture.

Selective Aerobic Oxidation of Cumene to Cumene Hydroperoxide over Mono- and Bimetallic Trimesate Metal–Organic Frameworks Prepared by a Facile “Green” Aqueous Synthesis

“…Therefore, in order to increase the CHP productivity, while maintaining the excellent selectivity to CHP, different catalysts have been proposed, either homogeneous or heterogeneous, mainly based on transition metal salts and oxides. [13][14][15][16][17][18][19][20][21] We and others have shown that several Metal-Organic frameworks (MOFs) can be used for the aerobic oxidation (i.e., using only air or oxygen as the oxidant) of activated alkanes, such as tetralin, 22 cyclooctane, 23 indane, 24 and various alkylbenzenes, 25 including cumene. Alternatively, MOFs can also be used as hosts in which other active species, such as metallo-phthalocyanines 26 or metal-oxide nanoparticles.…”

“…However, the productivity of such autoxidation processes (expressed in terms of grams of CHP produced per liter of CM and per hour; g L –1 h –1 ) is usually below the desired values. Therefore, in order to increase the CHP productivity, while maintaining the excellent selectivity to CHP, different catalysts have been proposed, either homogeneous or heterogeneous, mainly based on transition metal salts and oxides. − …”

Zeolite-Based Catalysis for Phenol Production

“…Transition metal complexes were also proposed as homogeneous catalysts. In this regard, Cu(II) complexes with nitrogenous macrocycles, 111 Co-, Zn-and Mn-porphyrins, 112 and Co-salen 113 have been used and have shown interesting results in terms of selectivity to CHP. However, these studies did not give rise to further developments.…”

A new highly active La2O3–CuO–MgO catalyst for the synthesis of cumyl peroxide by catalytic oxidation

“…Therefore, in order to solve this problem, it is very necessary to develop highly active and reusable homogeneous and heterogeneous catalysts for cumene oxidation to increase the productivity of CHP. Recent research on the liquid-phase oxidation of cumene-involved metal–organic frameworks (MOFs), 8,9 Salenalen-type complexes, 10 N -hydroxyphthalimide (NHPI), 11 ionic liquids, 12 and metal oxides as important research components. Many homogeneous catalysts can improve CHP yield under mild conditions, but they have become stumbling blocks in the process of catalyst preparation, product purification and recovery.…”