DFT Study of the Molybdenum‐Catalyzed Deoxydehydration of Vicinal Diols

Abstract

The mechanism of the molybdenum-catalyzed deoxydehydration (DODH) of vicinal diols has been investigated using density functional theory. The proposed catalytic cycle involves condensation of the diol with an Mo(VI) oxo complex, oxidative cleavage of the diol resulting in an Mo(IV) complex, and extrusion of the alkene. We have compared the proposed pathway with several alternatives, and the results have been corroborated by comparison with the molybdenum-catalyzed sulfoxide reduction recently published by Sanz et al. and with experimental observations for the DODH itself. Improved understanding of the mechanism should expedite future optimization of molybdenum-catalyzed biomass transformations.

Exploring the Reaction Pathways of Bioglycerol Hydrodeoxygenation to Propene over Molybdena‐Based Catalysts

“…Depending on the orientation of the glycerolm olecule on the surfacea nd possibly on the density of vacant sites, adsorptionm ay proceed with one or two OH groups.I nt he case of two OH attached to two neighboring bridging vacancies, ac yclic unstablei ntermediate can be formed to lead to 2-propenol. Analogous configurations were proposed by Shiramizu and To ste [62] and Lupp et al [63] 2-Propenol desorbs from the surface, which leaves the surface in the oxidizedf orm. Then, H 2 in turn regenerates vacancies and closes the catalytic cycle.…”

“…In the case of two OH attached to two neighboring bridging vacancies, a cyclic unstable intermediate can be formed to lead to 2‐propenol. Analogous configurations were proposed by Shiramizu and Toste and Lupp et al . 2‐Propenol desorbs from the surface, which leaves the surface in the oxidized form.…”

Vanadium‐Catalyzed Deoxydehydration of Glycerol Without an External Reductant

“…DFT calculations propose that the Re‐ and Mo‐catalysed DODH reaction in which alcohols are employed as reductants proceed by an inner‐sphere mechanism . Accordingly, the alcohol is bound to the metal centre it reduces.…”

New Motifs in Deoxydehydration: Beyond the Realms of Rhenium

“…The proposed mechanism was corroborated using DFT calculations, with the alkene extrusion proceeding through ar everse[ 3 + +2] cycloaddition similar to the mechanism proposed for rhenium-catalysed DODH. [61] The ability of molybdenum to cleave diols oxidatively has literature precedence. Pinacol hasb een used as ar eductantf or the molybdenum-catalysed deoxygenation of sulfoxides.…”