Bao N. Nguyen

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Organization: University of Leeds , England
Department: Institute of Process Research & Development
Title: Professor(PhD)
Co-reporter:Grant J. Sherborne;Sven Adomeit;Robert Menzel;Jabor Rabeah;Angelika Brückner;Mark R. Fielding;Charlotte E. Willans
Chemical Science (2010-Present) 2017 vol. 8(Issue 10) pp:7203-7210
Publication Date(Web):2017/09/25
DOI:10.1039/C7SC02859H
A mechanistic investigation of Ullmann–Goldberg reactions using soluble and partially soluble bases led to the identification of various pathways for catalyst deactivation through (i) product inhibition with amine products, (ii) by-product inhibition with inorganic halide salts, and (iii) ligand exchange by soluble carboxylate bases. The reactions using partially soluble inorganic bases showed variable induction periods, which are responsible for the reproducibility issues in these reactions. Surprisingly, more finely milled Cs2CO3 resulted in a longer induction period due to the higher concentration of the deprotonated amine/amide, leading to suppressed catalytic activity. These results have significant implications on future ligand development for the Ullmann–Goldberg reaction and on the solid form of the inorganic base as an important variable with mechanistic ramifications in many catalytic reactions.
Co-reporter:Michael R. Chapman, Maria H. T. Kwan, Georgina E. King, Benjamin A. Kyffin, A. John Blacker, Charlotte E. Willans and Bao N. Nguyen  
Green Chemistry 2016 vol. 18(Issue 17) pp:4623-4627
Publication Date(Web):14 Jul 2016
DOI:10.1039/C6GC01601D
A novel, rapid and efficient route to imidazo[1,2-a]pyridines under ambient, aqueous and metal-free conditions is reported. The NaOH-promoted cycloisomerisations of N-propargylpyridiniums give quantitative yield in a few minutes (10 g scale). A comparison of common green metrics to current routes showed clear improvements, with at least a one order of magnitude increase in space-time-yield.
Co-reporter:Michael R. Chapman;Susan E. Henkelis; Nikil Kapur;Dr. Bao N. Nguyen;Dr. Charlotte E. Willans
ChemistryOpen 2016 Volume 5( Issue 4) pp:351-356
Publication Date(Web):
DOI:10.1002/open.201600019

Abstract

Synthetic methods to prepare organometallic and coordination compounds such as Schiff-base complexes are diverse, with the route chosen being dependent upon many factors such as metal–ligand combination and metal oxidation state. In this work we have shown that electrochemical methodology can be employed to synthesize a variety of metal–salen/salan complexes which comprise diverse metal–ligand combinations and oxidation states. Broad application has been demonstrated through the preparation of 34 complexes under mild and ambient conditions. Unprecedented control over metal oxidation state (MII/III/IV where M=Fe, Mn) is presented by simple modification of reaction conditions. Along this route, a general protocol-switch is described which allows access to analytically pure FeII/III–salen complexes. Tuning electrochemical potential, selective metalation of a Mn/Ni alloy is also presented which exclusively delivers MnII/IV–salen complexes in high yield.

Co-reporter:Grant J. Sherborne; Michael R. Chapman; A. John Blacker; Richard A. Bourne; Thomas W. Chamberlain; Benjamin D. Crossley; Stephanie J. Lucas; Patrick C. McGowan; Mark A. Newton; Thomas E. O Screen; Paul Thompson; Charlotte E. Willans
Journal of the American Chemical Society 2015 Volume 137(Issue 12) pp:4151-4157
Publication Date(Web):March 13, 2015
DOI:10.1021/ja512868a
A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray absorption spectroscopy (XAS) at Ir L3-edge, Cl K-edge, and K K-edge. These culminate in in situ XAS experiments that link structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and “hot filtration” experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active precatalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide–iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure.
Co-reporter:Rachel Nicholls, Simon Kaufhold and Bao N. Nguyen  
Catalysis Science & Technology 2014 vol. 4(Issue 10) pp:3458-3462
Publication Date(Web):11 Jun 2014
DOI:10.1039/C4CY00480A
The first observation of guanidine–CO2 ‘activation’ complexes in solution using ATR-FTIR is reported. While cyclic guanidines TBD and MTBD form stable and detectable complexes with CO2, other guanidines and tertiary amines do not. Correlation with the catalytic activity of these amines/guanidines in the reaction between CO2 and propargylamines indicated that the basicity of the catalyst, rather than its ability to form complexes with CO2, is the origin of catalytic activity.
Co-reporter:Rachel Nicholls, Simon Kaufhold and Bao N. Nguyen
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 10) pp:NaN3462-3462
Publication Date(Web):2014/06/11
DOI:10.1039/C4CY00480A
The first observation of guanidine–CO2 ‘activation’ complexes in solution using ATR-FTIR is reported. While cyclic guanidines TBD and MTBD form stable and detectable complexes with CO2, other guanidines and tertiary amines do not. Correlation with the catalytic activity of these amines/guanidines in the reaction between CO2 and propargylamines indicated that the basicity of the catalyst, rather than its ability to form complexes with CO2, is the origin of catalytic activity.
Naphthalene, 1-(2,6-dimethylphenyl)-2-methoxy-
SILANE, (DICYCLOHEXYLMETHOXY)TRIETHYL-
SILANE, [1-(2-CHLOROPHENYL)ETHOXY]TRIETHYL-
Silane, triethyl[1-(2-furanyl)ethoxy]-
1H-Imidazole, 1,1'-[1,3-phenylenebis(methylene)]bis-
2-amino-1-(2-propyn-1-yl)-Pyridinium bromide
IMIDAZO[1,2-A]PYRIDINE, 6-IODO-2-METHYL-
1H-Imidazolium, 1,3-bis(phenylmethyl)-, bromide