An efficient and selective oxidation of benzylic and aromatic allylic alcohols with manganese dioxide supported on kieselguhr under solvent-free conditions

Wool supported manganese dioxide nano-scale dispersion: a biopolymer based catalyst for the aerobic oxidation of organic compounds

“…The results of our investigations have been compared to previous reports of MnO 2 . 6,8,9,11,[32][33][34][35] The results show that MnO 2 impregnated on wool is one of the best oxidant systems in reaction times and yield viewpoints (Table 7).…”

“…7 For this reason, it is important that at the end of the catalytic oxidation process, the MnO 2 is separable from supports. Although the procedure for separating MnO 2 from supports such as kieselguhr, 8 aluminum silicate, 9 alumina, 10 or silica, 11 has not been described before, but in our previous work 6 it was suggested that it possible to separate the MnO 2 from a bio-support by burning or chemical decomposing of biosupport.…”

Hierarchically Structured MnO2‐Co/C Nanocomposites: Highly Efficient and Magnetically Recyclable Catalysts for the Aerobic Oxidation of Alcohols

“…Herein, we report the synthesis of unprecedented hierarchically structuredm icrospheres composed of MnO 2 nanoplatelets, in whichC o/C nanoparticles are homogeneously distributed. The resulting material (denoted 4,F igure 1) functions as ah ighly efficient and selective catalyst in the aerobicoxidation of aliphatic and aromaticalcohols at ambient pressure;i to utperforms knownM nO 2 -based catalysts [20] andr ivals the activity of those based on palladium. [21] More importantly,o wing to homogeneous dispersion of Co/C nanoparticles, MnO 2 species are firmly anchored aroundt he magnetic component of the catalyst, which ensures efficient magnetic separation, as established over 10 reaction cycles in the oxidationo fb enzyl alcohol.…”

“…Under optimized reaction conditions (see the Supporting Information) ac atalyst loading of 3.8mol %w as sufficient to achievet he oxidation of benzyla lcohol to its corresponding aldehydei nh igh yields with excellent chemoselectivity (Table 1, entry 1) within 4h at 80 8C, whichc ompares favorably to all MnO 2 catalysts reported so far for such reactions. [11,20,33] For comparison, commercial MnO 2 showedv ery poor catalytic activity under the same conditions (Table 1, entry 2). With al ower catalyst loading of 4 (0.95 mol %), almostc omplete conversion of benzaldehyde could still be obtaineda fter prolonging the reaction time to 10 h( Ta ble 1, entry 3), and at urnover number (TON) of 93 was achieved.…”

“…Thus, significant leaching of manganese was observed upon application ( Figure S2), which led to as harp decrease in activity in consecutive catalytic runs (Figure 3c). Considering Pd 0 as the best catalyst for the title transformation, [20] we compared the kineticp rofiles for the aerobic oxidation of benzylalcohol catalyzed by 4 and by Pd 0 supported on activated carbon (Pd/C, 10 wt %). To ensure af air comparison, the latter reactionw as conducted under the optimal conditions reported, that is, at ar eaction temperature of 90 8C.…”