9Bio-derived furans such as 2-furfural (furfural), 5-hydroxymethyl-2-furfual (5-HMF) and 10 5-methyl-2-furfural (5-MF) was successfully transformed to ketoacid, levulinic acid 11 (LA), and diketones, 1-hydroxyhexane-2,5-dione (1-HHD), 3-hydroxyhexane-2,5-dione 12 (3-HHD) and hexane-2,5-dione (HD), at moderate reaction conditions using water 13 soluble and recyclable 8-aminoquinoline coordinated arene-ruthenium(II) complexes. At 14 the optimized condition using 1 mol % catalyst in the presence of 12 equivalent formic 15 acid at 80 ~ 100 °C, complete conversion of furfural to LA with high selectivity was 16 achieved. Several experiments along with 1 H NMR spectral studies are described which 17 provide more insights into the mechanism of the transformation of furans to open ring 18 components. Experiment performed using structural analogues of active catalyst inferred 19 a structural-activity relationship for the observed superior catalytic activity of the 8-20 aminoquinoline coordinated arene-ruthenium(II) complex. Furthermore, due to high 21 aqueous solubility of the studied complexes, high recyclability, up to 4 catalytic runs, 22 was achieved without any significant loss of activity. Molecular identities of the studied 23 8-aminoquinoline coordinated arene-ruthenium(II) complex was also confirmed by 24 single-crystal X-ray diffraction studies. Development of new methodologies and catalysts for the transformation of biomass and 2 biomass derived compounds into biofuel components are highly desirable to reduce the 3 global dependence on the fossil fuel resources. Moreover, these transformations of 4 biomass can also produce several value added chemicals for potential applications in 5 chemical industries. However, direct usage of biomass is unsuitable so far. 1-7 In this 6 regard, furans, an important feedstock of biomass obtained by selective dehydration of 7 hexose and pentose sugar, are considered as an important resource for the production of 8 bio-based chemicals. 8-19 Furan derivatives such as 5-HMF, furfural and 5-MF are being 9 used as valuable C5/C6 resources for the synthesis of value added chemicals and biofuel 10 components based on LA, succinic acid, ketones, 1,6-hexanediol, cyclopentanone, adipic 11 acid, caprolactam, caprolactone, furoic acid and so on. 20-36 Moreover, C5-C9 alkane can 12 also be produced by the hydrolytic ring opening and complete hydrogenation of furans 13 and its aldol adducts. 36-38 14 Ketoacids and diketones have been successfully used to produce several value 15 added fine chemicals such as esters, alcohols, lactones, amines and cycloketones. 39-41 16 According to US-DOE, LA (ketoacid) has been identified as one of the 12 important 17 target chemicals in their biomass program. 41 Due to the presence of carbonyl group, 18 carboxylic group and α-H in LA, various sorts of compounds can be synthesized by 19 different type of reactions like halogenation, esterification, hydrogenation, condensation 20 etc. that can be used in drugs, agriculture, food, cosmetics and spice industry (...

Efficient tandem catalytic transformations of bioderived furans, such as furfural, 5‐hydroxymethylfurfural (5‐HMF), and 5‐methylfurfural (5‐MF), to levulinic acid (LA) and diketones, 1‐hydroxyhexane‐2,5‐dione (1‐HHD), 3‐hydroxyhexane‐2,5‐dione (3‐HHD), and hexane‐2,5‐dione (2,5‐HD), was achieved by using water‐soluble arene–RuII complexes, containing ethylenediamine‐based ligands, as catalysts in the presence of formic acid. The catalytic conversion of furans depends on the catalyst, ligand, formic acid concentration, reaction temperature, and time. Experimental evidence, including time‐resolved 1H NMR spectral studies, indicate that the catalytic reaction proceeds first with formyl hydrogenation followed by hydrolytic ring opening of furans. The ruthenium–formic acid tandem catalytic transformation of fructose to diketones and LA was also achieved. Finally, the molecular structures of the four representative arene–RuII catalysts were established by single‐crystal X‐ray diffraction studies.

Bimetallic Ni1−xPdx (0.10≤x≤0.75) alloy nanoparticle catalysts were synthesised and successfully employed for the catalytic aerial oxidation of biomass‐derived furans, such as 2‐furfuraldehyde (furfural), 2‐furfuryl alcohol (furfuryl alcohol), 5‐hydroxymethyl‐2‐furfural (5‐HMF), 5‐methyl‐2‐furfural (MF) and 5‐methyl‐2‐furfuryl alcohol (MFA), to selectively afford the corresponding furan carboxylic acids (2‐furoic acid, furan‐2,5‐dicarboxylic acid (FDCA) and 5‐methyl‐2‐furoic acid (MFCA)) in water at 80 °C. Among the studied Ni1−xPdx nanoparticle catalysts, Ni0.90Pd0.10 nanoparticle catalyst outperformed the others, achieving high yields of the corresponding furan carboxylic acid products. The presence of Ni in the Ni1−xPdx nanoparticle catalysts was advantageous, because it not only enhanced the catalytic activity for the facile oxidation of biomass‐derived furans using aerial oxygen to achieve high catalytic turnover, but also provided excellent stability to the Ni0.90Pd0.10 nanoparticle catalyst towards air and water and thus significantly enhanced its recyclability (up to 10 catalytic runs). The experiments revealed that the catalytic oxidation of 5‐HMF proceeded by the initial oxidation of the formyl group to carboxylic acid, and, subsequently, the conversion of alcohol to carboxylic acid via the formyl group to form FDCA. Moreover, the one‐pot direct transformation of fructose to furan carboxylic acid products (such as FDCA) was also achieved by using the Ni0.90Pd0.10 nanoparticle catalyst.

A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products.