A versatile cobalt(II)-Schiff base catalyzed oxidation of organic substrates with dioxygen: Scope and mechanism

Epoxidation of alkenes with molecular oxygen and isobutyraldehyde catalyzed by immobilized vitamin B12 within Al-MCM-41

“…Based on the oxidation mechanism, especially on those studied by Iqbal and co-workers on versatile cobalt(II)-Schiff bases catalyzing the oxidation of organic substrates [19], Co(III) superoxo and Co(IV)-oxo intermediates have been thought to be responsible for oxygen transfer to the substrates. Since vitamin B 12 immobilized within Al-MCM-41 contains six ligands around the central cobalt cation, the formation of the active superoxo and oxo species is not possible unless the breakage of a bond to cobalt occurs prior to the approach and attachment of the oxidant to the central cobalt cation.…”

Epoxidation of olefins with oxygen/isobutyraldehyde over transition-metal-substituted phosphomolybdic acid on SBA-15

“…Recently, considerable interests have been drawn on studying the aerobic epoxidation of olefins for developing more efficient and environmentally benign route [4][5][6][7]. It was reported that aerobic epoxidation of olefins in solution can be efficiently achieved under quite mild conditions over some transition metal complexes by using molecular oxygen as oxidant and aliphatic aldehyde as co-reactant, which is the so-called "Mukaiyama" procedure [8][9][10][11][12][13]. Although the usage of co-reactant aldehyde is undesirable, the Mukaiyama method is still worthy of studying for its great advantages, such as very mild operation conditions (low temperatures, atmospheric pressure), high epoxide selectivity, low cost and environmental-friendly nature of the oxidant [11][12][13].…”

“…In general, Mukaiyama epoxidation could be catalyzed by using some homogeneous transition metal complexes like ␤-diketonate complexes, Schiff's base complexes, metal cyclam complexes and metalloporphyrins complexes [8][9][10][11][12][13]. For overcoming the separation and recycling problems of the homogeneous catalysts, recent efforts were mainly focused on preparing efficient heterogeneous catalysts [14][15][16][17][18][19][20][21][22][23].…”

Co2+-exchanged SAPO-5 and SAPO-34 as efficient heterogeneous catalysts for aerobic epoxidation of alkenes

“…It is well known that transition metal complexes, such as Schiff's base complexes, metalloporphyrin complexes and metal cyclam complexes, exhibit high activity for the aerobic epoxidation of alkenes [18][19][20]. However, theses homogeneous catalysts prepared by relatively complicated procedures are difficult to be recycled.…”