EcoMnOx, a Biosourced Catalyst for Selective Aerobic Oxidative Cleavage of Activated 1,2-Diols

Abstract

A novel catalyst, EcoMnOx, was prepared from waste biomass of Mn-hyperaccumulating plants. The valorization of this Mn-rich biomass is an alternative to its costly usual disposing and provides a new source of Mn. Extracted metal ions, including Mn 2+ , were oxidized in mild conditions by H 2 O 2 /NaOH to afford EcoMnOx, as a polymetallic oxide material containing from 8.9 to 14.1 wt % Mn. Spectroscopic studies of this material revealed the presence of Mn layered mixed oxides, rich in Mn IV along with Mn III and Mn II species. EcoMnOx catalytic properties were assessed in the aerobic oxidative cleavage of 1,2-diols, under atmospheric pressure of O 2 or air. With only 10 mol % Mn, up to complete conversions were obtained on activated benzylic and allylic diols, with excellent selectivity toward aldehydes or ketones (98− 99%). Moreover, because of its heterogeneous nature, the catalyst can be removed easily by filtration, and reapplied for a minimum of six successive runs without any loss of activity. Finally, E-factor analysis showed the EcoMnOx generates 4 to 17 times less waste compared to classical reagents such as NaIO 4 and Pb(OAc) 4 , respectively, highlighting the sustainable assets of this new heterogeneous catalyst.

Eco‐Mn Ecocatalysts: Toolbox for Sustainable and Green Lewis Acid Catalysis and Oxidation Reactions

“…– Eco‐Mn OX2 : Eco‐Mn LA is oxidized by hydrogen peroxide in the presence of a large excess of sodium hydroxide. The precipitate formed is composed of a mixture of Mn oxides: Na 0.55 Mn 2 O 4 .1.5H 2 O, MnO(OH), Mn 3 O 4 and CaMn 3 O 8 (Scheme ) …”

“…If the experimental conditions allow the preservation of all the metallic elements of Eco‐Mn LA , it is not true for Eco‐Mn Ox . Table illustrates the metallic compositions of Eco‐Mn LA catalysts and Eco‐Mn Ox2 catalysts . The treatment eliminates 2/3 of the Fe present in Eco‐Mn LA in favor of a higher rate of Mn.…”

“…The precipitate formed is composed of a mixture of Mn oxides: Na 0. 55 [35] -Eco-Mn OX3 : Eco-Mn LA is supported on montmorillonite K10, then added to the substrate and treated by a mixture of sodium bicarbonate and hydrogen peroxide (Scheme 6). [36] If the experimental conditions allow the preservation of all the metallic elements of Eco-Mn LA , it is not true for Eco-Mn Ox .…”

“…Table 2 illustrates the metallic compositions of Eco-Mn LA catalysts and Eco-Mn Ox2 catalysts. [35] The treatment eliminates 2/3 of the Fe present in Eco-Mn LA in favor of a higher rate of Mn. The polymetallic nature of the ecocatalyst is however preserved with an interesting mixture of Mn/Ca/Mg.…”

Oxidative C−C Cleavage of Ketols over Vanadium–Carbon Catalysts

“…As a result of the non‐green nature of such oxidants, catalytic systems in which O 2 is used as an oxidant have been sought. Typical catalysts for oxidative C−C cleavage with O 2 are based on Ru, Mn, Cu, and V . Ru and Mn catalysts can convert aromatic vicinal diol to aldehydes in good yields and they are less effective for aliphatic substrates, especially under neutral or acidic conditions.…”