Glycolaldehyde as a Bio-Based C₂ Platform Chemical: Catalytic Reductive Amination of Vicinal Hydroxyl Aldehydes

Abstract

Reductive amination of glycolaldehyde (GA), the smallest sugar molecule and obtainable from biomass, creates a versatile platform for ethylamine products, potentially replacing current pathways via toxic ethylene oxide and dichloroethane. Given the high reactivity of α-OH carbonyls, the main challenge was control of selectivity in a cascade of parallel and consecutive reactions during reductive amination. The type of solvent and catalyst, preferably methanol and Pd, respectively, are key enabling parameters to achieve high product yields. A kinetic study on product intermediates accompanied with detailed product analysis (MS and NMR) suggested a general mechanistic scheme and validation with density functional theory calculations provided a rational understanding of the solvent effect in terms of energetics and kinetics. Primary alkanolamines (AA) such as 2-(dimethylamino)-ethanol are preferred products, and large excess of the amine reagent is not required to reach almost quantitative yields. Interestingly substoichiometric amine-to-GA ratio allows for high yield of higher (consecutive) AAs such as N-methyldiethanolamine (MDEA) and triethanolamine, for which a peculiar cyclic 5-membered oxazolidinic precursor was analyzed (e.g., for reaction with monomethylamine to MDEA). The shift to diamine-selective (DA) reactions is possible by switching to a two-step one-pot approach. With ethylene glycol as a preferred solvent, high yield of an unsaturated C 2 -enediamine precursor is obtained under an inert atmosphere, followed by its metal-catalyzed hydrogenation at elevated temperature to the final DA product such as N,N,N′,N′-tetramethylethylene-diamine. A conceptual model of the catalytic reductive amination routes that allows production of a variety of ethylamines with up to +90 C % yield is thus presented. The successful preparation and sensory assessment of a GA-based diester quat in fabric softener formulations demonstrates the viability of a full bio-based and drop-in production route for high-value chemicals, directly from GA as a platform molecule.

Thermal Cracking of Sugars for the Production of Glycolaldehyde and Other Small Oxygenates

“…[11] For achemical industry based on renewable feedstocks, new platform molecules will be needed. [12] Glycolaldehyde (hydroxyacetaldehyde) may be one such platform molecule for ab iomass-based chemical industry.G lycolaldehyde can be transformed into other useful chemicals, such as ethyl-ene glycol by catalytic hydrogenation, [13] glycolic acid by mild oxidation, [14] methyl vinyl glycolate (MVG), [15][16][17] and ethanol amines [18][19][20] (Scheme 1).…”

Dependency of solvation effects on metal identity in surface reactions

“…The role of solvents in catalytic transformations occurring at a solid-liquid interface is typically ascribed to: heightened importance of mass transfer effects, nature of solvent (polarity etc.) [35][36][37] , competitive adsorption between solvent molecules and adsorbed moieties 32,38,39 , direct participation of the solvent in the reaction coordinate 40 , and/or relative stabilization of reactant, transition and/or product state of elementary reactions [41][42][43] . These effects in turn can lead to a change in reaction mechanism, reaction kinetics, selectivity, and overall catalyst lifetime.…”

Toward Replacing Ethylene Oxide in a Sustainable World: Glycolaldehyde as a Bio‐Based C2 Platform Molecule

“…Furthermore, the five‐membered oxazolidinic intermediate obtained by Faveere et al. shows strongly resembles the nucleoside pentose but with the incorporation of a nitrogen atom [181] . This could potentially serve as a synthetic N‐containing nucleoside analogue (also called azanucleoside) for the development of new antitumour or antiviral drugs [203, 204] .…”

“…For example, Faveere et al. demonstrated a two‐step one‐pot approach to obtain ethylenediamines from GA [181] . Methanol as a solvent was shown to further enhance the reductive aminolysis rate by lowering the activation barriers for nucleophilic amine attack and C−C bond scission.…”

“…Faveere et al. recently showed the versatility of GA as a substrate of reductive amination reactions [181] . A variety of parameters was investigated, enabling the selectivity to be fine‐tuned between alkanolamines, ethylenediamines, and higher alkanolamines in a one‐step process (Scheme 6).…”