Iron-catalysed chemo-selective oxidation of unprotected sugars: application for the competitive oxidation of pentoses from a sugar mixture

Abstract

An iron-catalysed transfer hydrogenation methodology was developed to oxidise aldo-hexoses and -pentoses into sugar lactones using different acceptors. The transformation occurs on unprotected sugars with complete chemo-selectivity for the anomeric...

Nanoarchitectonics of Non-Noble-Metal-Based Heterogeneous Catalysts for Transfer Hydrogenation Reactions: Detailed Insights on Different Hydrogen Sources

“…11,26−28 In the CTH process, there are three possibilities of hydrogen transfer, which were classified by Braude and Linstead 29 as (i) transfer of hydrogen taking place within one molecule; (ii) hydrogen disproportionation occurs, which leads to the transfer of hydrogen between identical donor and acceptor molecules; and (iii) transfer hydrogenation−dehydrogenation occurs between unlike donor and acceptor molecules. 30,31 Currently, the hydrogen donors, such as alcohols, formic acid, and hydrazine hydrate are majorly utilized for the transfer hydrogenation reactions. The study of CTH methodology for organic reactions has experienced substantial growth over the decade spanning from 2014 to 2024, as shown in Figure 1.…”

“…To overcome these problems and because of the drive toward a green and sustainable future, CTH from suitable hydrogen sources such as formic acid, alcohols, hydrazine hydrate, water, etc., have attracted a tremendous amount of attention for hydrogenation reactions. The main advantages of this methodology involves the following: a high-pressure reactor is not needed, simple stirring is required, there is a reduction in complexity and cost of experiment, it is easy to handle, possible casualties are minimized, and there is more selectivity in reduction reactions. ,− In the CTH process, there are three possibilities of hydrogen transfer, which were classified by Braude and Linstead as (i) transfer of hydrogen taking place within one molecule; (ii) hydrogen disproportionation occurs, which leads to the transfer of hydrogen between identical donor and acceptor molecules; and (iii) transfer hydrogenation–dehydrogenation occurs between unlike donor and acceptor molecules. , Currently, the hydrogen donors, such as alcohols, formic acid, and hydrazine hydrate are majorly utilized for the transfer hydrogenation reactions. The study of CTH methodology for organic reactions has experienced substantial growth over the decade spanning from 2014 to 2024, as shown in Figure .…”

Gold-Catalyzed Oxidative Transformation of Free Sugars into Biobased Platform Molecules

“…22−28 Only one recent article reports the direct oxidation of unprotected sugars into lactones via a catalytic transfer hydrogenation pathway, using iron catalyst and acetone as both acceptor and solvent. 29 Interestingly, among other homogeneous and heterogeneous metal catalysts, Au NPs were demonstrated to be efficient for obtaining aliphatic lactones 30−33 or methyl esters 34−40 from diols, under mild aerobic conditions. Nevertheless, to the best of our knowledge, these procedures have never been applied to saccharidic (and polyhydroxylated) substrates.…”

“…On the other hand, sugar lactones can be obtained directly from aldoses, albeit traditional procedures involve either hazardous strong oxidants (chromium, bromine, iodine, etc. ), harmful solvents (DMF, CH 2 Cl 2 ) and/or partially protected sugars. − Only one recent article reports the direct oxidation of unprotected sugars into lactones via a catalytic transfer hydrogenation pathway, using iron catalyst and acetone as both acceptor and solvent . Interestingly, among other homogeneous and heterogeneous metal catalysts, Au NPs were demonstrated to be efficient for obtaining aliphatic lactones − or methyl esters − from diols, under mild aerobic conditions.…”