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Iridium-catalyzed highly efficient chemoselective reduction of aldehydes in water using formic acid as the hydrogen source
Green Chem., 2017, Advance Article DOI: 10.1039/C7GC01289F, Paper
Zhanhui Yang, Zhongpeng Zhu, Renshi Luo, Xiang Qiu, Ji-tian Liu, Jing-Kui Yang, Weiping Tang A highly efficient iridium catalyst is developed for the chemoselective reduction of aldehydes to alcohols in water, using formic acid as a reductant.
bFaculty of Science, Beijing University of Chemical Technology, Beijing, P. R. China
cSchool of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing, P. R. China
dSchool of Pharmacy, Gannan Medical University, Ganzhou, P. R. China
eDepartment of Chemistry, University of Wisconsin–Madison, Madison, USA
A water-soluble highly efficient iridium catalyst is developed for the chemoselective reduction of aldehydes to alcohols in water. The reduction uses formic acid as the traceless reducing agent and water as a solvent. It can be carried out in air without the need for inert atmosphere protection. The products can be purified by simple extraction without any column chromatography. The catalyst loading can be as low as 0.005 mol% and the turn-over frequency (TOF) is as high as 73800 mol mol−1 h−1. A wide variety of functional groups, such as electron-rich or deficient (hetero)arenes and alkenes, alkyloxy groups, halogens, phenols, ketones, esters, carboxylic acids, cyano, and nitro groups, are all well tolerated, indicating excellent chemoselectivity.
It has been calculated that the enthalpy of formation of Cp-5 is 2782.2 kJ mol−1, while its detonation velocity and pressure are 3282 km s−1 and 4.443 GPa, respectively.112 Upon complete combustion, the total heat of combustion for Cp-5 is 2.17 × 105 kJ mol−1 due to its high carbon content. It seems that this compound may not be useful as the main ingredient of an explosive or a propellant but it might be a good additive for heat-generating energetic compositions. To improve the energetic content of fullerene derivatives, more nitro groups can be introduced on the fullerene skeleton. Such a strategy has been recently attempted, where a high-nitrogen-content derivative, C60(NO2)14 (FP, CP-10), was prepared and characterized,113 using a prolonged treatment of C60 in benzene with very high concentrations of N2O4. However, Cp-10 is not so thermally stable and it deflagrates when heated above 170 °C in nitrogen or air, releasing a considerable amount of heat. This compound may be used as a powerful explosive, depending on its sensitivity, which has not been reported. In addition to the nitro-derivatives of fullerene, fullerene nitrates have also been reported that can be used in propellant compositions as energetic burn rate modifiers. As a typical example, fullerene ethylenediamine nitrate (Cp-11, FEDN) was synthesized by reacting fullerene and ethylenediamine in diluted nitric acid (Scheme ).114
112 B. Tan, R. Peng, H. Li, B. O. Jin, S. Chu and X. Long, Theoretical investigation of an energetic fullerene derivative, J. Comput. Chem., 2010, 31, 2233–2237 CAS.
113 F. Cataldo, O. Ursini and G. Angelini, Synthesis and explosive decomposition of polynitrofullerene, Carbon, 2013, 62, 413–421 CrossRefCAS.
114 B.-L. Chen, B. Jin, R.-F. Peng, F.-Q. Zhao, J.-H. Yi, W.-J. Han, H.-J. Guan and S.-J. Chu, Synthesis and characterization of fullerene-ethylenediamine nitrate, Chin. J. Energet. Mater., 2014, 22, 186–191 CAS.
Efficient and stereoselective syntheses of isomerically pure 4-aminotetrahydro-2H-thiopyran 1-oxide derivatives have successfully been achieved. Isomerically pure (4-nitrophenyl)sulfonyltetrahydro-2H-thiopyran 1-oxides were identified by X-ray crystallographic analyses, and isomerically pure sulfoxide derivatives were characterized by 1H NMR. An oxidation reaction of tert-butyl(4-nitrophenyl)sulfonyl(tetrahydro-2H-thiopyran-4-yl)carbamate with Oxone provided steric control, affording its trans sulfoxide with high efficiency and selectivity. From the obtained trans sulfoxide derivatives, cis sulfoxide derivatives were synthesized conveniently by a hydrogen chloride catalyzed isomerization.
bInstitute of Organic Chemistry, RWTH Aachen University, Aachen D52074, Germany
Acetalization reactions play significant roles in the synthetically important masking chemistry of carbonyl compounds. Herein we demonstrate for the first time that tropylium salts can act as organic Lewis acid catalysts to facilitate acetalization and transacetalization reactions of a wide range of aldehyde substrates. This metal-free method works efficiently in both batch and flow conditions, prompting further future applications of tropylium organocatalysts in green synthesis.
Dr. Vinh Nguyen (also known as: Thanh Vinh Nguyen or Thanh V. Nguyen on academic publication) was born in Vietnam. After high school, he went to Sydney, Australia to study industrial chemistry at University of New South Wales. He then moved to undertake his PhD in organic chemistry with Professor Michael Sherburn at the Australian National University, Canberra. He had worked to develop new synthetic methodologies for application in natural product synthesis and worked on the design and synthesis of enormoussynthetic host molecules for drug-delivery modelling. After graduating in 2010, he came to work on organocatalysis in Professor Dieter Enders group at the Institute of Organic Chemistry, RWTH Aachen, Germany under the auspices of an Alexander von Humboldt Postdoctoral Fellowship. In June 2013, he moved to Curtin University (Perth, Australia) to start his own independent research group. In June 2015, he moved again to UNSW (Sydney) to take up a Lecturer/DECRA fellow position at the School of Chemistry. His current research interests are organocatalysis, aromatic cation activation, synthesis of naturally occurring and bioactive compounds, asymmetric synthesis and medicinal chemistry.
Selected Awards and Academic Achievements
2016: The 2016 Athel Beckwith Lectureship from RACI Organic Chemistry Division
2015-2018: ARC Discovery Early Career Researcher Award (DECRA)
2014: Thieme Chemistry Journal Award for outstanding early career academics.
2011 – 2013: Alexander von Humboldt Postdoctoral Fellowship (RWTH Aachen, Germany).
2005: The Era Polymer Prize for “The Best Honor Research Thesis” in Industrial Chemistry – UNSW
2000: Silver medal in the 32nd International Chemistry Olympiad in Copenhagen, Denmark
Nguyen’s group focuses their research on development of new synthetic methodologies in organic chemistry, organocatalysis and natural product synthesis.
Aromatic Cation Activation:
A new method for the nucleophilic substitution of alcohols and carboxylic acids and other substrates using aromatic tropylium cation activation has been developed. It demonstrates, for the first time, the synthetic potential of tropylium cations in promoting chemical transformations. (http://pubs.acs.org/doi/abs/10.1021/ol5003972).
Warning: Although no incidents occurred, the intermediates generated, as well as the end product, are energetic and should be handled as if they are explosive materials. It is essential that all reactions be conducted behind a blast shield and that proper protective equipment, including a face shield, be worn at all times during the operation.
A new procedure for the synthesis and isolation of methyl nitroacetate is described. The previously published method required drying the explosive dipotassium salt of nitroacetic acid in a vacuum desiccator, followed by grinding this material into a fine powder with a mortar and pestle prior to esterification. To obtain the desired product, benzene was employed as the extraction solvent, sodium sulfate was used as the drying agent, and two distillations were required. The new procedure eliminates drying and grinding of the explosive dipotassium salt, employs ethyl acetate or dichloromethane as the extraction solvent, eliminates the need for a drying agent, and requires a single distillation to furnish the end product in high yield and purity.