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49 results on '"Gu, Liuqun"'

10. 1H NMR Elucidation of Observed Stable Sugar‐NaCl‐water Complexes in Aqueous Solution.

Author

Zhu, Gan, Li, Hui, Li, Yiqun, and Gu, Liuqun

Subjects
AQUEOUS solutions, BIOMASS chemicals, MONOSACCHARIDES, CHEMICAL amplification, ATOMIC interactions, HYDROGEN bonding, FRUCTOSE
Abstract

The solvation of sugars in aqueous media matters in the understanding of biological systems and carbohydrate transformations. The presence of NaCl is known to perturb hydrogen bonding of sugar hydrates, however, direct evidence to elucidate mechanism at atom level is very rare even though the "NaCl Effect" was well known in biomass transformations for chemicals/biofuels. Here we report experimental evidences of a clear staircase‐like correlation between induced 1H NMR changes of D‐glucose/fructose with concentration of NaCl aqueous solution at room temperature; and two stable bonding status was observed in the system. HDO in sugar/NaCl aqueous solution as a "dynamic" reference is a key to enable decoupling the global salt effect in this 1H NMR investigation of NaCl‐saccharide interaction. Via a further half‐quantitative study, three structures of stable sugar‐NaCl‐water complexes were mapped for the first time in tackling the NaCl‐monosaccharide interaction at atomic level in an aqueous solution. Based on the maximum of induced 1H NMR shifts, an ideal NaCl usage was proposed. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Vitamin B1-Catalyzed Acetoin Formation from Acetaldehyde: A Key Step for Upgrading Bioethanol to Bulk C4 Chemicals.

Author

Lu, Ting, Li, Xiukai, Gu, Liuqun, and Zhang, Yugen

Subjects
RENEWABLE energy source research, FEEDSTOCK, VITAMIN B1, ACETOIN, CHEMICALS
Abstract

The production of bulk chemicals and fuels from renewable biobased feedstocks is of significant importance for the sustainability of human society. The production of ethanol from biomass has dramatically increased and bioethanol also holds considerable potential as a versatile building block for the chemical industry. Herein, we report a highly selective process for the conversion of ethanol to C4 bulk chemicals, such as 2,3- butanediol and butene, via a vitamin B1 (thiamine)-derived Nheterocyclic carbene (NHC)-catalyzed acetoin condensation as the key step to assemble two C2 acetaldehydes into a C4 product. The environmentally benign and cheap natural catalyst vitamin B1 demonstrates high selectivity (99%), high efficiency (97% yield), and high tolerance toward ethanol and water impurities in the acetoin reaction. The results enable a novel and efficient process for ethanol upgrading. [ABSTRACT FROM AUTHOR]

Published
2014
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47. Arylboronic acids catalyzed upgrade of glucosamines for deoxyfructosazine and insights on reaction mechanism

Author

Wang, Meifeng, Zhu, Gan, Li, Yiqun, and Gu, Liuqun

Abstract

Chitin is the most abundant N-containing polysaccharide in nature and d-glucosamine is one of the most successful commercial monomer products in the current market. Here we reported an arylboronic acids catalyzed upgrade of glucosamines in aqueous solution for deoxyfructosazine which is an important high-value compound in pharmaceutical and food industries, as well as a promising bio-based platform molecule for speciality chemicals and sustainable functional materials. Such direct integration of deoxyfructosazine into development of renewable chemicals/functional materials might be a practical way for utilization of chitin as a renewable nitrogen source. A mechanism focusing on a catalytic cycle of arylboronic acid via a boron transfer was also proposed.

Published
2022
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48. 4,4′-Disubstituted L-Prolines as Highly Enantioselective Catalysts for Direct Aldol Reactions

Author

Gu, Liuqun, Yu, Menglong, Wu, Xiaoyu, Zhang, Yazhu, and Zhao, Gang

Abstract

A new series of 4,4′-disubstituted prolines (1a–h) has been developed and tested as organocatalysts in the direct catalytic asymmetric aldol reaction of several aliphatic ketones with aldehydes. Catalyst 1g affords the best enantioselectivities for this transformation. The reaction was carried out in DMF using a catalyst loading of 10 mol % at −10 °C to give the aldol products in up to 97 % ee for acetone. In the cases of cyclohexanone and cyclopentanone, the corresponding anti-products were obtained in 94 % ee.

Published
2006
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49. Unexpected CO2 splitting reactions to form CO with N-heterocyclic carbenes as organocatalysts and aromatic aldehydes as oxygen acceptors.

Author

Gu L and Zhang Y

Subjects
Carbon Monoxide chemistry, Carboxylic Acids chemical synthesis, Carboxylic Acids chemistry, Catalysis, Methane chemistry, Molecular Structure, Aldehydes chemistry, Carbon Dioxide chemistry, Carbon Monoxide chemical synthesis, Heterocyclic Compounds chemistry, Methane analogs & derivatives, Oxygen chemistry
Abstract

The catalytic reduction of carbon dioxide to carbon monoxide under mild conditions using aromatic aldehydes as reductants and NHCs as organocatalysts was developed. This carbon dioxide splitting reaction provides a new method for metal-free carbon dioxide reduction and steps forward in utilizing carbon dioxide as a renewable "green" source under mild conditions. On the other hand, this reaction also shows a new economical way to oxidize aromatic aldehydes under mild conditions with carbon dioxide and could be applied in pharmaceutical synthesis.

Published
2010
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