Ewoud

Quantitative operando FlowNMR analysis of phosphite-modified hydroformylation catalysts reveals the reasons for their superior activity and stability, and gives insight into catalyst speciation during turnover.

Abstract

Phosphites are industrially important ligands for the Rh-catalysed hydroformylation of olefins because they produce more active catalysts than phosphines, which is mainly due to their strong π-acceptor properties facilitating CO dissociation from the metal centre. Herein, the effect of three prominent phosphite ligands (triphenylphosphite, Alkanox and BiPhePhos) on catalyst speciation during turnover is investigated using multi-nuclear operando FlowNMR spectroscopy. The quantitative catalyst distribution maps derived explain activity trends across a range of catalytic reaction conditions that show how phosphites produce more active catalysts, including reduced formation of inactive Rh⁰ dimers in the absence of substrate during pre-activation and at the end of the reaction. Additionally, [(alkanox)Rh(acac)] complexes have been found to be of high stability which can be exploited for post-catalytic Rh recovery by simple addition of 2,4-pentanediones.

Polymeric ionic liquids for conversion of cellulose into levulinic acid: A high levulinic acid yield of 79.4 % was achieved when used cellulose as substrates and sulphonic acid-functionalized polymeric ionic liquids as catalyst.

Abstract

Sulphonic acid-functionalized polymeric ionic liquids (PILs) were synthesized and applied into catalytic conversion of cellulose into levulinic acid (LA). The structure, thermal stability, and Hammett acidity function (H₀) of PILs were characterized and all were more thermostable than those of small-molecular ionic liquids (IL). At the optimum reaction conditions, the LA yield was maximized to 79.4 % by catalyst [Pim]CH₃SO₃. More importantly, catalyst [Pim]CH₃SO₃ performed well in other biomass conversion, such as cellobiose, starch and rice husk. The product LA can be easily extracted by methyl isobutyl ketone from the reaction mixture. The PILs with high catalytic activity were easily recycled with an LA yield up to 68.9 % even after five cycles. These sufficient PILs will offer new approaches for transforming biomass to platform chemicals.

A versatile synthesis of highly demanded α-hydroxycarboxylic acids via dehydrogenative coupling of two feedstock chemicals, ethylene glycol, and primary alcohols, is reported. An Earth's abundant metal complex catalyzes the reaction with high yields and selectivities. Water and hydrogen gas are produced as the sole byproducts.

Abstract

Herein, we report a straightforward synthesis of valuable α-hydroxycarboxylic acid molecules via an acceptorless dehydrogenative coupling of ethylene glycol and primary alcohols. A bench-stable manganese complex catalyzed the reaction, which is scalable, with the product being isolated with high yields and selectivities under mild conditions. The protocol is environmentally benign, producing water and hydrogen gas as the only byproducts. Methanol can also be used as a C1 source for producing the platform molecule lactic acid, with a high turnover of >10⁴. The methodology was also used to functionalize alcohols derived from natural products and fatty acids. Furthermore, it was applied for synthesizing α-amino acid, α-thiocarboxylic acid, and several drugs and bioactive molecules, including endogenous metabolites, Danshensu, Enalapril, Lisinopril, and Rosmarinic acid. Preliminary mechanistic studies were performed to shed light on the mechanism involved in the reaction.

Nature Communications, Published online: 14 January 2023; doi:10.1038/s41467-023-35925-2

Nature, Published online: 13 January 2023; doi:10.1038/d41586-023-00063-8

Give your chemistry classroom a green overhaul with resources from the American Chemical Society Green Chemistry Institute, Beyond Benign, and the Center for Green Chemistry & Green Engineering at Yale. Many green chemistry online resources, journals, and textbooks for classroom and laboratory are available. Urgent adoption of these resources is needed.

Abstract

Full integration of green chemistry into the undergraduate curriculum is a necessity to prepare our students for a sustainable future. We discuss the reasons for the need to change the curriculum, the institutions in North America, Europe, and Asia that are leading the way towards integration with classroom resources, and the published textbooks that are currently available for both classroom and laboratory. We plead for more time for hard-pressed college professors to revamp the curriculum, and for these efforts to be valued. We feel compelled by the urgency of this need to implore the chemistry education community to participate in these efforts now.

Nature Communications, Published online: 19 November 2022; doi:10.1038/s41467-022-34708-5

Nature, Published online: 23 November 2022; doi:10.1038/d41586-022-03791-5