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Friday, 29 July 2016

Ring-locking enables selective anhydrosugar synthesis from carbohydrate pyrolysis


Ring-locking enables selective anhydrosugar synthesis from carbohydrate pyrolysis

Green Chem., 2016, Advance Article
DOI: 10.1039/C6GC01600F, Paper
Li Chen, Jinmo Zhao, Sivaram Pradhan, Bruce E. Brinson, Gustavo E. Scuseria, Z. Conrad Zhang, Michael S. Wong
The nonselective nature of glucose pyrolysis chemistry can be controlled by preventing the sugar ring from opening and fragmenting.

Ring-locking enables selective anhydrosugar synthesis from carbohydrate pyrolysis

*Corresponding authors
aDepartment of Chemical and Biomolecular Engineering, Rice University, Houston, USA
E-mail: mswong@rice.edu
bDepartment of Chemistry, Rice University, Houston, USA
cDalian National Laboratory of Clean Energy, Dalian Institute of Chemical Physics, Dalian, China
E-mail: zczhang@dicp.ac.cn
dDepartment of Civil and Environmental Engineering, Rice University, Houston, USA
eDepartment of Materials Science and NanoEngineering, Rice University, Houston, USA
Green Chem., 2016, Advance Article
DOI: 10.1039/C6GC01600F
The selective production of platform chemicals from thermal conversion of biomass-derived carbohydrates is challenging. As precursors to natural products and drug molecules, anhydrosugars are difficult to synthesize from simple carbohydrates in large quantities without side products, due to various competing pathways during pyrolysis. Here we demonstrate that the nonselective chemistry of carbohydrate pyrolysis is substantially improved by alkoxy or phenoxy substitution at the anomeric carbon of glucose prior to thermal treatment. Through this ring-locking step, we found that the selectivity to 1,6-anhydro-β-D-glucopyranose (levoglucosan, LGA) increased from 2% to greater than 90% after fast pyrolysis of the resulting sugar at 600 °C. DFT analysis indicated that LGA formation becomes the dominant reaction pathway when the substituent group inhibits the pyranose ring from opening and fragmenting into non-anhydrosugar products. LGA forms selectively when the activation barrier for ring-opening is significantly increased over that for 1,6-elimination, with both barriers affected by the substituent type and anomeric position. These findings introduce the ring-locking concept to sugar pyrolysis chemistry and suggest a chemical-thermal treatment approach for upgrading simple and complex carbohydrates.
////////Ring-locking ,  selective anhydrosugar, carbohydrate pyrolysis, synthesis

Tuesday, 19 July 2016

2-chloro-3-(3-chloro-5-iodophenoxy)-4-(trifluoromethyl)pyridine




2-chloro-3-(3-chloro-5-iodophenoxy)-4-(trifluoromethyl)pyridine


1H NMR (400 MHz, DMSO-d6) δ 8.65 (d, J = 4.9 Hz, 1H), 7.95 (t, J = 4.5 Hz, 1H), 7.60 (dd, J = 1.3, 2.9Hz, 1H), 7.38 (br. s., 1H), 7.29 - 7.15 (m, 1H)


13C NMR (101 MHz, DMSO-d6) δ 157.10, 148.02, 145.37, 142.46 (q, JC-F = 2.0 Hz), 135.00, 132.82 (q,JC-F = 33.2 Hz), 131.69, 122.91, 121.59 (q, JC-F = 4.0 Hz), 121.34 (q, JC-F = 273.7 Hz), 115.47, 95.72

19F NMR (377 MHz, DMSO-d6) δ -61.96 (s, 1F)
mp 71.69-79.27 °C






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Monday, 11 July 2016

Nickel-Catalyzed Decarbonylative Suzuki–Miyaura Coupling of Amides To Generate Biaryls

Thumbnail image of graphical abstract








Shi et al. have reported a nickel-catalyzed decarbonylative Suzuki–Miyaura reaction which uses an N-aroylpiperidine-2,6-dione as the coupling partner for the boronic acid ( Angew. Chem., Int. Ed. 2016556959−6963).
The method is attractive from the point of view of the stability of N-aroylpyrrolidine-2,5-diones toward storage and manipulation and the flexibility they add to the chemist’s toolbox, given their preparation from a different group of precursors to aryl halides or triflates.
Notably, the reaction uses an air-stable and inexpensive nickel catalyst, and the reactions tolerate the presence of water. While a standard reaction temperature of 150 °C is quoted, the use of temperatures as low as 80 °C also seem to be possible. Coupling efficiency is reported to be adversely affected when the aromatic rings of both of the coupling partners bear electron-donating substituents.
Ortho substituents on the aromatic rings seem to be beneficial as they facilitate decarbonylation as part of the cross-coupling. Oxidative addition into the N–C(aroyl) bond of the amide is proposed as initiating the catalytic cycle and is possible on account of a reduction in the resonance stabilization of the N-aroyl functionality versus a conventional aromatic amide.

Suzuki–Miyaura Coupling

Synthesis of Biaryls through Nickel-Catalyzed Suzuki–Miyaura Coupling of Amides by Carbon–Nitrogen Bond Cleavage (pages 6959–6963)Shicheng Shi, Guangrong Meng and Prof. Dr. Michal Szostak
Version of Record online: 21 APR 2016 | DOI: 10.1002/anie.201601914
Thumbnail image of graphical abstract
Breaking and making: The first nickel-catalyzed Suzuki–Miyaura coupling of amides for the synthesis of biaryl compounds through N−C amide bond cleavage is reported. The reaction tolerates a wide range of sensitive and electronically diverse substituents on both coupling partners.
STR1
STR1
1H NMR (500 MHz, CDCl3) δ 7.70 (s, 4 H), 7.61 (d, J = 7.3 Hz, 2 H), 7.48 (t, J = 7.6 Hz, 2 H), 7.42 (t, J = 7.3 Hz, 1 H).

STR1
13C NMR (125 MHz, CDCl3) δ 144.87, 139.92, 129.48 (q, J F = 32.5 Hz), 129.13, 128.32, 127.56, 127.42, 125.83 (q, J F = 3.8 Hz), 124.46 (q, J F = 270.0 Hz).

STR1
19F NMR (471 MHz, CDCl3) δ -62.39.



Szostak_PhotoMichal Szostakemail: michal.szostak@rutgers.edu
office: Olson 204
  1. Department of Chemistry, Rutgers University, Newark, NJ, USA

CHEM_BANNER

Research Interests

The central theme of our research is synthetic organic and organometallic chemistry with a focus on the development of new synthetic methods based on transition metal catalysis and various aspects of transition metal mediated free radical chemistry and their application to the synthesis of biologically active molecules.

Selected Publications

  1. Graphene-Catalyzed Direct Friedel-Crafts Alkylation Reactions: Mechanism, Selectivity and Synthetic Utility. Hu, F.; Patel, M.; Luo, F.; Flach, C.; Mendelsohn, R.; Garfunkel, E.; He, H.; Szostak, M. J. Am. Chem. Soc. 2015137 [doi]
  2. General Olefin Synthesis by the Palladium-Catalyzed Heck Reaction of Amides: Sterically-Controlled Chemoselective N-C Activation. Meng, G.; Szostak, M. Angew. Chem. Int. Ed. 201554[doi]
  3. Aminoketyl Radicals in Organic Synthesis: Stereoselective Cyclization of 5- and 6-Membered Cyclic Imides to 2-Azabicycles using SmI2-H2O. Shi S.; Szostak, M. Org. Lett. 201517, 5144 [doi]
  4. Sterically-Controlled Pd-Catalyzed Chemoselective Ketone Synthesis via N-C Cleavage in Twisted Amides. Meng, G.; Szostak, M. Org. Lett. 201517 [doi]
  5. Recent Developments in the Synthesis and Reactivity of Isoxazoles: Metal Catalysis and Beyond.Hu, F.; Szostak, M. Adv. Synth. Catal. 2015357, 2583. [doi]
  6. Determination of Structures and Energetics of Small- and Medium-Sized One-Carbon Bridged Twisted Amides using ab Initio Molecular Orbital Methods. Implications for Amidic Resonance along the C-N Rotational Pathway. Szostak, R.; Aubé, J.; Szostak, M. J. Org. Chem. 201580, 7905. [doi]
  7. An Efficient Computational Model to Predict Protonation at the Amide Nitrogen and Reactivity along the C-N Rotational Pathway. Szostak, R.; Aubé, J.; Szostak, M. Chem. Commun. 201551, 6395.[doi]
  8. Pd-Catalyzed C-H Activation: Expanding the Portfolio of Metal-Catalyzed Functionalization of Unreactive C-H Bonds by Arene-Chromium π-Complexation. Hu, F.; Szostak, M. ChemCatChem20157, 1061. [doi]
  9. Highly Chemoselective Reduction of Amides (Primary, Secondary and Tertiary) to Alcohols using SmI2/H2O/Amine under Mild Conditions. Szostak, M.; Spain, M.; Eberhart, A. J.; Procter, D. J. J. Am. Chem. Soc. 2014136, 2268. [doi]
  10. Substrate-Directable Electron Transfer Reactions. Dramatic Rate Enhancement in the Chemoselective Reduction of Cyclic Esters using SmI2-H2O: Mechanism, Scope and Synthetic Utility. Szostak, M.; Spain, M.; Choquette, K. A.; Flowers, R. A., II; Procter, D. J. J. Am. Chem. Soc.2013135, 15702. [doi]
  11. Selective Reduction of Barbituric Acids using SmI2-H2O: Synthesis, Reactivity and Structural Analysis of Tetrahedral Adducts. Szostak, M.; Spain, M.; Behlendorf, M; Procter, D. J. Angew. Chem. Int. Ed. 201352, 12559. [doi]
  12. Non-Classical Lanthanide(II) Iodides: Uncovering the Importance of Proton Donors in TmI2-Promoted Electron Transfer. Facile C-N Bond Cleavage in Unactivated Amides. Szostak, M.; Spain, M.; Procter, D. J. Angew. Chem. Int. Ed. 201352, 7237. [doi]
  13. Chemistry of Bridged Lactams and Related Heterocycles. Szostak, M.; Aubé, J. Chem. Rev. 2013,113, 5701. [doi]
For more detail, please see the Szostak Group Web Site 


DSC_0080




GROUP


Prof. Michal Szostak
Assistant Professor
Ph.D., University of Kansas (2009) with Jeffrey Aubé
Postdoctoral, Princeton University (2010) with David MacMillan
Postdoctoral, University of Manchester (2011-2014) with David Procter 
Postdoctoral Researchers
Dr. Feng Hu
Ph.D., Nanjing University, 2009 (Z. Huang)
Postdoctoral, Shanghai Institute of Materia Medica (Y. Hu)
Research Assistant Professor, SIOC (Q. Shen)
Postdoctoral, Lamar University (X. Lei) 
Dr. Pradeep Nareddy
Ph.D., University of Geneva, 2013 (C. Mazet)
Postdoctoral, Leipzig University (C. Schneider) 
Graduate Students
Shicheng Shi
M.S., SIOC, 2013 (R. Wang)
B.S., Nanjing Agriculture University, 2010 
Guangrong Meng
M.S., Fudan University, 2014 (Q. Zhang)
B.S., Dalian Medical University, 2011 
Chengwei Liu
M.S., Soochow University, 2014 (Y. Yao)
B.S., Zaozhuang University, 2011 
Undergraduate Students
Syed Huq (Rutgers, Chemistry, 2014-present)
Marcel Achtenhagen (Rutgers, Chemistry, 2015-present) 
Visiting Students
Yongmei Liu (Yangzhou University, R. Liu)

//////Nickel-Catalyzed,  Decarbonylative Suzuki–Miyaura Coupling,  Amides, Biaryls

Wednesday, 6 July 2016

Understanding the chemistry behind the antioxidant activities of butylated hydroxytoluene (BHT): A review

imageHighlights
Modification of BHT has a significant multivariate effect on antioxidant efficiency.
BDE is the key to rational design and development of antioxidants.
Antioxidant performance of BHT is mainly depending on 13 very crucial parameters.
MPAO is a promising way to increase antioxidant and pharmacological activities.

Abstract

Hindered phenols find a wide variety of applications across many different industry sectors. Butylated hydroxytoluene (BHT) is a most commonly used antioxidant recognized as safe for use in foods containing fats, pharmaceuticals, petroleum products, rubber and oil industries. In the past two decades, there has been growing interest in finding novel antioxidants to meet the requirements of these industries. To accelerate the antioxidant discovery process, researchers have designed and synthesized a series of BHT derivatives targeting to improve its antioxidant properties to be having a wide range of antioxidant activities markedly enhanced radical scavenging ability and other physical properties. Accordingly, some structure–activity relationships and rational design strategies for antioxidants based on BHT structure have been suggested and applied in practice. We have identified 14 very sensitive parameters, which may play a major role on the antioxidant performance of BHT. In this review, we attempt to summarize the current knowledge on this topic, which is of significance in selecting and designing novel antioxidants using a well-known antioxidant BHT as a building-block molecule. Our strategy involved investigation on understanding the chemistry behind the antioxidant activities of BHT, whether through hydrogen or electron transfer mechanism to enable promising anti-oxidant candidates to be synthesized.

Volume 101, 28 August 2015, Pages 295–312
Review article

Understanding the chemistry behind the antioxidant activities of butylated hydroxytoluene (BHT): A review

  • aNanotechnology & Catalysis Research Centre, (NANOCAT), University of Malaya, Block 3A, Institute of Postgraduate Studies Building, 50603 Kuala Lumpur, Malaysia
  • bDepartment of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
  • cDivision of Human Biology, Faculty of Medicine, International Medical University, 57000 Kuala Lumpur, Malaysia
  • dDrug Design and Development Research Group, Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
  • http://www.sciencedirect.com/science/article/pii/S022352341530101X
doi:10.1016/j.ejmech.2015.06.026
SEE
https://www.researchgate.net/publication/278050005_ChemInform_Abstract_Understanding_the_Chemistry_Behind_the_Antioxidant_Activities_of_Butylated_Hydroxytoluene_BHT_A_Review/figures












///////////Antioxidant, Butylated hydroxytoluene, Free radical, Reactive oxygen species, Phenol