Ruthenium‐Catalyzed CC Bond Cleavage in Lignin Model Substrates

Abstract

Ruthenium-triphos complexes exhibited unprecedented catalytic activity and selectivity in the redox-neutral C-C bond cleavage of the β-O-4 lignin linkage of 1,3-dilignol model compounds. A mechanistic pathway involving a dehydrogenation-initiated retro-aldol reaction for the C-C bond cleavage was proposed in line with experimental data and DFT calculations.

Selective Depolymerisation of γ‐Oxidised Lignin via NHC Catalysed Redox Esterification

“…Thus, a beech butanosolv lignin was prepared according to previous reports [18] and the oxidation of the primary alcohol groups to aldehydes in Scheme 1. Previously reported two-step oxidative approaches to lignin depolymerisation via a) secondary [6][7][8][9][10][11] or b) primary alcohol [12][13][14] oxidation of native type β-aryl ether linkages lignin compared to this work c) employing selective oxidation and NHC catalysis for the depolymerisation of butanosolv lignin βaryl ether linkages. the β-aryl ether linkages was attempted using the biphasic TEMPO/NCS catalytic system developed by Einhorn et al [22] In contrast to our previous reports on the direct TEMPO-catalysed oxidation of this alcohol to carboxylic acids, [23] attempts to perform this reaction on the butanosolv lignin failed to provide the expected aldehyde product.…”

Médaille Lavoisier: J. Livage / New Members of the Academia Europaea Science Award Electrochemistry: B. D. McCloskey / Ernst Haage Prize: I. Siewert / Einstein Visiting Fellowship: D. W. Stephan

“…Stephan was featured here when he won the British Royal Society of Chemistry Ludwig Mond Award . He has recently reported in Angewandte Chemie on metal‐free catalytic olefin hydrogenation …”

Full Utilization of Lignocellulose with Ionic Liquid Polyoxometalates in a One‐Pot Three‐Step Conversion

“…[4][5][6][7] However,t he traditional methods of hydrogenolysis often suffer from high temperature and high H 2 pressure, which result in low-functional products.The methods also suffer because it is more difficult to separate the solid catalysts from the remaining cellulose/hemicellulose for further conversion to more products. [11] For selectiveo xidation transformations,t he modelc ompoundsc an be cleaved by inserting oxygen atoms to form high-value-added chemicals such as phenol, aldehydes, ketones,a nd organic acids by using variousc atalysts. [8][9][10] During lignin depolymerization, model compounds with differentl inkages of b-O-4, a-O-4, and4 -O-5 are often selected to study the selectivec leavage of chemical bonds in lignin.…”

“…Amongt he linkages, the b-O-4 motif is considered as the typical unit and the most abundant linkage, which composes up to 70 %o fl ignin. [11] For selectiveo xidation transformations,t he modelc ompoundsc an be cleaved by inserting oxygen atoms to form high-value-added chemicals such as phenol, aldehydes, ketones,a nd organic acids by using variousc atalysts. The aerobic oxidation of 2-phenoxy-1-phenylethanol [PP-ol, (a), Figure1]i sn oted as undergoing severalm ultiply competitive pathways such as breaking of the b-O-4 bond to phenol and acetophenone, cleavage of the b-O-4 bond to benzaldehyde, oxidation of the hydroxy group to PP-one, and further oxidation of breakage products to benzoica cid.…”