Switchable Alkene Epoxidation/Oxidative Cleavage with H₂O₂/NaHCO₃: Efficient Heterogeneous Catalysis Derived from Biosourced Eco-Mn

Abstract

International audienceA novel Mn-derived catalyst was prepared starting from the biomass of Mn-hyperaccumulating plants growing on metal-rich soils. Recovery of this biomass as value-added ``ecocatalyst'' provides incentives for the development of phytoextraction programs on soils degraded by mining activities. Characterization of the resulting plant-based catalyst Eco-Mn by inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), and X-ray photoelectron spectroscopy (XPS) demonstrated the presence of unusual polymetallic complexes of Mn(II) in the catalyst, along with Fe(III). Incorporation of these species into montmorillonite K10 as solid support provided a supported Eco-Mn catalyst, whose properties were investigated for alkene epoxidation with H2O2 (30 wt %)/NaHCO3 (0.2 M) as a green terminal-oxidizing reagent. The supported Eco-Mn catalyst demonstrated a high efficiency for styrene epoxidation, with only 0.31 mol % Mn, a much lower content of Mn than in previously described Mn-derived heterogeneous catalysts. Although Fe was also present in the supported Eco-Mn catalyst, comparison experiments showed that Fe had only a limited role in the catalysis. The water content in the reaction medium had a beneficial effect, increasing the reaction efficiency. The supported Eco-Mn catalyst was recycled four times without any loss of activity. Comparison of its properties to those of heterogeneous catalysts made by incorporation of commercial MnCl2 center dot 4H(2)O and FeCl3 center dot 6H(2)O highlighted the superior catalytic activity of polymetallic species present in the biosourced catalyst. The substrate scope of the method was extended to various alkenes, including bulky natural products which were epoxidized with high yields (up to 99%), sometimes much higher than those obtained with already described Mn-derived heterogeneous catalysts. Finally, by simple adjustments of reaction conditions, the method allowed controlled access to aldehydes by oxidative cleavage of various styrene-derived substrates (up to 93% yield). The method thus constitutes a valuable alternative not only to classical epoxidation reagents but also to oxidative cleavage of styrene-derived molecules, which usually involves toxic and hazardous reagents

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

“…– 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 ) …”

“…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.…”

“…Among the diols studied, the superoxidized products, as carboxylic acids, were not detected. [36] Eco-Mn Ox3 catalyst is an unusual polymetallic complex of Mn(II) and Fe(III). Eco-Mn Ox3 was incorporated in Montmorillonite K10 giving a supported catalyst that was used to catalyze the epoxidation of alkenes with a mixture of H 2 O 2 (30 % w/w)/ NaHCO 3 (0.2 M) as a green terminal oxidative reagent.…”

From Conventional Lewis Acids to Heterogeneous Montmorillonite K10: Eco‐Friendly Plant‐Based Catalysts Used as Green Lewis Acids

“…The yellow solution is concentrated under vacuum then filtered through a pad of Celite if a purification step is necessary. The resulting solid residue, stored in a desiccator, may be used as an ecocatalyst or may be supported on silica or MK10 …”

Ecological Recycling of a Bio-Based Catalyst for Cu Click Reaction: a New Strategy for a Greener Sustainable Catalysis

“…Multicomponent reactions, Diels‐Alder and domino reactions are particularly efficient. Soft oxidation reactions like epoxidation or the chaining in situ of the oxidation/epoxide opening/oxidative cleavage sequence could be compared favourably with the current industrial processes to access platform molecules. The polymetal systems obtained from the biomass produced by phytoextraction are original (unusual oxidation levels, new associated chemical species, effects of synergy).…”