Catalytic Reductive Aminolysis of Reducing Sugars: Elucidation of Reaction Mechanism

Carbon-Supported Ru-Ni and Ru-W Catalysts for the Transformation of Hydroxyacetone and Saccharides into Glycol-Derived Primary Amines

Nitrogen-containing molecules are used for the synthesis of polymers, surfactants, agrochemicals, and dyes. In the context of green chemistry, it is important to form such compounds from bioresource. Short-chain primary amines are of interest for the polymer industry, like 2-aminopropanol, 1-aminopropan-2-ol, and 1,2-diaminopropane. These amines can be formed through the amination of oxygenated substrates, preferably in aqueous phase. This is possible with heterogeneous catalysts, however, effective systems that allow reactions under mild conditions are lacking. We report an efficient catalyst Ru-Ni/AC for the reductive amination of hydroxyacetone into 2-aminopropanol. The catalyst has been reused during 3 cycles demonstrating a good stability. As a prospective study, extension to the reactivity of (poly)carbohydrates has been realized. Despite a lesser efficiency, 2-aminopropanol (9 % yield of amines) has been formed from fructose, the first example from a carbohydrate. This was possible using a 7.5 %Ru-36 %WxC/AC catalyst, composition allowing a one-pot retro-aldol cleavage into hydroxyacetone and reductive amination. The transformation of cellulose through sequential reactions with a combination of 30 %W2C/AC and 7.5 %Ru-36 %WxC/AC system gave 2 % of 2-aminopropanol, corresponding to the first example of the formation of this amine from cellulose with heterogeneous catalysts.

Photocatalytic Production of Ethanolamines and Ethylenediamines from Bio-Polyols over a Cu/TiO2 Catalyst

Valorization of biomass-derived polyols into high-value-added ethanolamines and ethylenediamines is highly attractive. Herein, we report a one-step photocatalytic protocol to convert bio-polyols into a 60 % yield of ethanolamines and ethylenediamines over a multifunctional Cu/TiO2 catalyst. This catalyst enables a tandem process of photocatalytic polyol C-C bond cleavage and reductive amination in one pot at room temperature, and also allows the selective conversion of various bio-polyols and amines. Mechanistic studies revealed that photogenerated holes in TiO2 promote the retro-aldol C-C bond cleavage or oxidative dehydrogenation of polyols, and photogenerated electrons accumulate on small-sized Cu clusters, which facilitate the reductive amination via hydrogen transfer and prevent the H2 generation. This strategy provides new opportunities for the development of non-noble metal photocatalysts and methods of biomass conversion under mild conditions.

Single-Step Sustainable Production of Hydroxy-Functionalized 2-Imidazolines from Carbohydrates

Manufacturing valuable N-containing chemicals from biomass is highly desirable yet challenging. Herein, a novel strategy was developed for efficient production of 2-(1-hydroxyethyl)-imidazoline (HI), a high-value and versatile building block for synthesizing a myriad of bioactive targets, directly from carbohydrates under mild reaction conditions. With this strategy, bio-based HI was produced from fructose in one step with as high as 77 C % isolated yield in the presence of ethylenediamine (EDA) and InCl₃ at 130 °C. The synergistic functions of EDA and InCl₃ were identified for the transformation, wherein EDA promoted the scission of C-C bond of fructose backbone via retro-aldol (R-A) reaction and rapidly trapped in-situ formed reactive carbonyl-containing C₃ intermediate for HI formation to avoid undesired side reaction, and InCl₃ facilitated the formation of this C₃ intermediate and the final 1,2-hydrid shift step.

Providing direction for mechanistic inferences in radical cascade cyclization using Transformer model

Even in modern organic chemistry, predicting or proposing a reaction mechanism and speculating on reaction intermediates remains challenging. For example, it is challenging to predict the regioselectivity of radical attraction...

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

Fossil-based platform molecules such as ethylene and ethylene oxide currently serve as the primary feedstock for the C₂ -based chemical industry. However, in the search for a more sustainable chemical industry, fossil-based resources may preferentially be replaced by renewable alternatives, provided there is realistic economic feasibility. This Review compares and critically discusses several production routes toward bio-based structural analogues of ethylene oxide and the required adaptations for their implementation in state-of-the-art C₂ -based chemical processes. For example, glycolaldehyde, a structural analogue obtainable from carbohydrates by atom-economic retro-aldol reactions, may replace ethylene oxide's leading role. This alternative chemical route may not only allow the carbon footprint of conventional chemicals production to be lowered, but the introduction of a bio-based pathway may also contribute to safer production processes. Where possible, challenges, drawbacks, and prospects are highlighted.

N-formyl-stabilizing quasi-catalytic species afford rapid and selective solvent-free amination of biomass-derived feedstocks

Nitrogen-containing compounds, especially primary amines, are vital building blocks in nature and industry. Herein, a protocol is developed that shows in situ formed N-formyl quasi-catalytic species afford highly selective synthesis of formamides or amines with controllable levels from a variety of aldehyde- and ketone-derived platform chemical substrates under solvent-free conditions. Up to 99% yields of mono-substituted formamides are obtained in 3 min. The C-N bond formation and N-formyl species are prevalent in the cascade reaction sequence. Kinetic and isotope labeling experiments explicitly demonstrate that the C-N bond is activated for subsequent hydrogenation, in which formic acid acts as acid catalyst, hydrogen donor and as N-formyl species source that stabilize amine intermediates elucidated with density functional theory. The protocol provides access to imides from aldehydes, ketones, carboxylic acids, and mixed-substrates, requires no special catalysts, solvents or techniques and provides new avenues for amination chemistry.

Processes for efficient production of primary, secondary or ternary aminated compounds are constant challenges for chemical and pharmaceutical industries. Here, the authors develop selective and sustainable amination chemistry widely applicable to chemical substrates via formic acid.