Oxidation of benzyl alcohols by semi-stoichiometric amounts of cobalt-doped birnessite-type layered MnO₂under oxygen atmosphere

Abstract

Semi-stoichiometric oxidation of benzylic alcohols to benzaldehydes was readily achieved in heated toluene in the presence of cobalt-doped birnessite MnO 2 under oxygen atmosphere. The oxidation took place selectively for benzylic alcohols, while allylic alcohols were oxidized slowly. No oxidation occurred for usual primary and secondary alcohols. Oxygen atmosphere was important to perform effective oxidation; i.e. the oxidation progressed much slower in nitrogen atmosphere. Cobalt-doped birnessite was the best catalyst for the oxidation, in which the amount of birnessite was reduced to 0.7 equivalent of alcohol, resulting in yields of aldehydes greater than 80%. The present method provides a useful green oxidation for benzylic alcohols.

Nanostructured MnO2 as Electrode Materials for Energy Storage

“…The Co/Ni doping did not modify the 1D nanostructure of α -MnO 2 , because of the growth mechanism of the dissolution–recrystallization process. Co-doped birnessite (Co-bir) δ -MnO 2 is a catalyst synthesized by a modified sol-gel method for the oxidation of benzylic alcohols to benzaldehydes achieved in heated toluene under oxygen atmosphere [161]. The enhanced electrical conductivity of δ -MnO 2 is attributed to location of Co 2+ ions in the octahedral lattice.…”

Rational Low‐Temperature Synthesis of Ultrasmall Nanocrystalline Manganese Binary Oxide Catalysts under Controlled Metal Cation Hydration in Organic Media

“…Because manganese adopts multiple oxidation states, its oxides can act as oxidants [10][11][12][13][14] and catalysts [15][16][17][18][19][20] in various oxidative transformations. The catalytic performances of eight newly synthesized nanocrystalline manganese binary oxides (Table 1) were investigated for aerobic oxidative transformations.…”

“…Nanocrystalline metal oxides benefitf rom large specific surface areas and short ion diffusion lengths, which may facilitatee fficient surface reactiona nd rapid ion extraction/insertion neededi nh igh-performance functional materials. [1][2][3][4][5][6][7][8][9] Manganese binary oxides have attractedt remendous attention because of their potentialu ses as oxidants, [10][11][12][13][14] catalysts, [15][16][17][18][19][20] electrode materials, [3][4][5][6][7] and adsorbents. [21][22][23][24][25][26][27][28][29][30] For example, LiÀ Mn spinel oxide has served as cathode material for lithium-ion batteries [3][4][5][6][7] and Li + ion-selective adsorbents [21,24,28] because its structuree nables the electrochemical and/orc hemical extrac-tion and insertion of Li + ions.…”

Photodegradation of dyes by a novel TiO2/u-RuO2/GNS nanocatalyst derived from Ru/GNS after its use as a catalyst in the aerial oxidation of primary alcohols (GNS = graphene nanosheets)

“…On the other hand, the cobalt-doped birnessite (Co-Bir) catalytic system gave 84% of the same product from benzyl alcohol only after 24 h even under aerobic condition [27]. Similarly, benzyl alcohols containing substituents such as -NO 2 , -OCH 3 or -CH 3 at para position were effectively oxidized to the corresponding aldehydes in good to moderate yields without affecting the selectivity (Table 1, …”