Deoxydehydration of Polyols

Abstract

The development of sustainable chemical processes for the conversion of highly oxygenated biomass feedstocks to chemical products requires efficient and selective processes for partial oxygen removal and refunctionalization. Here we review the development of the deoxydehydration (DODH) reaction, which converts vicinal diols (glycols) to olefins. Uncatalyzed deoxygenative eliminations were first established. The catalyzed DODH reactions have largely employed oxo-rhenium catalysts and a variety of reductants, including PR₃, dihydrogen, sulfite, and alcohols. A variety of glycol and biomass-derived polyol substrates undergo the DODH reaction in moderate to good efficiency, regioselectively, and stereoselectively. Observations regarding selectivity, mechanistic probes, and computational studies support the general operation of a catalytic process involving three basic stages: glycol condensation to an M-glycolate, reduction of the oxo-metal, glycol condensation to produce a metal-glycolate, and alkene extrusion from the reduced metal-glycolate. Recent practical developments include the discovery of non-precious V- and Mo-oxo DODH catalysis.

Rhenium‐Catalyzed Deoxydehydration of Diols and Polyols

“…[11] It has been highlighted twice, [12,13] been the subtopic of two reviews, [14,15] and recently both the uncatalyzed and transition-metal-catalyzed DODH were treated in a book chapter; [16] within the past two years, more than ten papers dealing with mechanistic investigations [17][18][19] and the development of new rhenium-based catalysts, [20,21] reductants, [22,23] substrates, [24,25] and catalysts based on other elements [26][27][28] have been published, and we therefore think that the time has come for a dedicated Minireview. [11] It has been highlighted twice, [12,13] been the subtopic of two reviews, [14,15] and recently both the uncatalyzed and transition-metal-catalyzed DODH were treated in a book chapter; [16] within the past two years, more than ten papers dealing with mechanistic investigations [17][18][19] and the development of new rhenium-based catalysts, [20,21] reductants, [22,23] substrates, [24,25] and catalysts based on other elements [26][27][28] have been published, and we therefore think that the time has come for a dedicated Minireview.…”

Synthesis of Cyclopentadienyl‐Based Tricarbonyl Rhenium Complexes and Some Unusual Reactivities of Cyclopentadienyl Substituents

“…[34] After the completion of the reaction, the purple suspension was centrifuged, and the solvent was decanted to afford an insoluble off-white solid. The comparatively weak donor strength of the Cp′ ligand in 14a was further corroborated by a (Re-CO) 13 C NMR signal at relatively low field (δ = 194.7 ppm) and the corresponding (ReC-O) sym IR vibration at ν = 2013 cm -1 ( Table 2). The solid did not dissolve in CH 2 Cl 2 , CHCl 3 , acetone, pyridine, or dimethyl sulfoxide (DMSO) and was not analyzed further.…”

“…Accordingly, 14 13 C NMR signals were found, including a singlet at δ = 194.14 ppm for the Re-CO moiety, which appeared in a similar range for 10a (δ = 195.7 ppm) and 11a (δ = 195.6 ppm). J. Inorg.…”

“…Owing to the volatile prices of fossil fuels and their anticipated depletion, the search for alternative and renewable feedstocks has received much attention. [6,7] Particularly attractive is the combination of deoxygenation [8,9] and dehydration [10] in the single-step deoxydehydration (DODH) [11][12][13] of biomass-derived sugars and polyols to obtain the corresponding deoxygenated olefinic products. [3][4][5] However, in contrast to petroleum-derived hydrocarbons, its components are highly oxygenated, mostly in the form of hydroxy groups.…”

Vanadium‐Catalyzed Deoxydehydration of Glycerol Without an External Reductant

“…DODH has the ability to reduce the oxygen content of biomass efficiently and retain useful functionality. Since 2009, DODH and particularly Re‐catalysed DODH have received renewed focus because of their success with biomass‐derived substrates . Nonetheless, the allure of glycerol as a substrate has been present from the onset.…”