Day 1 :
Keynote Forum
Benjamin Murray
The City College of New York & The Graduate Center CUNY, USA
Keynote: An investigation into the mechanism of transmetalation of primary and secondary alkylboron nucleophiles in palladium-catalyzed Suzuki reactions
Biography:
Benjamin Murray completed his master’s in chemistry from the University of Glasgow (Scotland) in 2013. Additionally, as part of this degree, he worked for one year in the lab of Prof. Overkleeft at Leiden University (Netherlands). He has since been working towards his Ph.D. in the Biscoe Lab of City College of New York, where he is expecting to defend this Spring. His current research has focused on the transmetalation step in the Suzuki reaction and has recently had work published in the journal Science.
Abstract:
Through the past 40 years, carbon-carbon crosscoupling reactions have greatly enhanced the ability of chemists to synthesize C(sp2)-C(sp2) bonds and more recently C(sp2)-C(sp3) bonds. In particular, the Suzuki-Miyaura reaction has proven to be invaluable with its high yields, good functional group tolerance, and low toxicity of reagents. One of the component steps of the catalytic cycle of this reaction is transmetalation, in which the nucleophilic species transfers its organic component to the metal center (generally palladium). The mechanism of transfer from primary alkyl boron nucleophiles was studied in the 1990s via the use of deuteriumlabeled probes and analysis by NMR, giving evidence to this being a stereo retentive SE2 mechanism. Subsequent work on secondary systems has highlighted the plausibility of both retentive and invertive mechanisms of transmetalation in Suzuki reactions. More recent research highlighted that the enantiospecific of such C(sp2)-C(sp3) reactions is not reliant solely upon the nucleophilic species. The selectivity is influenced by multiple factors including the ligand electronics, ligand steric, electrophile electronics, as well as the inclusion of exogenous additives. This poster will lay out the findings of the parameters that affect the transmetalation mechanism for primary and secondary trifluoroborate nucleophiles in cross-coupling reactions. The prominent use of NMR to decipher between gauche and anti-staggered vicinal protons on deuterium-labeled alkyl probes in order to determine mechanistic information of the transmetalation of primary alkyl boron nucleophiles will be demonstrated.
- Clinical Chemistry, Medicinal Chemistry, Analytical Chemistry, Organic Chemistry, Agricultural & Food Chemistry.
Location: WEBINAR
Session Introduction
Ahmed M Hameed
Umm Al-Qura University, KSA
Title: Development of chromatographic methods to follow heterogeneous organic chemistry in aerosols
Biography:
Ahmed M. Hameed is Assistant Professor of Analytical chemistry at Umm Al-Qura University in Makkah, KSA. His research is in three main areas: the first is the development of methods to directly observe fundamental gas phase kinetics of key reactions of atmospheric importance in the laboratory. The second area of work focuses on the development of novel analytical techniques to quantify trace species in the atmosphere and the third area is on the investigation of trace elements in drinking water. He is also teaching analytical and environmental chemistry modules
Abstract:
urrently, there is considerable interest in the environmental effects of aerosols as they have an effect on public health, air quality and climate. From a chemical perspective, aerosol particles can support heterogeneous chemical reactions and participate in multiphase processes, which affect the distribution and abundance of atmospheric trace gases. Chemical and physical processes are some of the most poorly quantified areas of climate science and therefore represent some of the largest uncertainties in predictive climate models. Atmospheric aldol self-reactions of octanal, heptanal, and hexanal in a range of aqueous H2SO4 w/v% concentrations as a catalyst were studied in both bulk liquid-liquid experiments and gas-liquid experiments. Initially, a new practical methodology was developed and enhanced to monitor aldol reactions in aqueous acidic media. The evaluation of the quenching and extracting method was performed, confirming the suitability, reliability, and reproducibility of the extraction method. In bulk studies, aldol products of the three aldehydes were separated and identified by preparative HPLC, GC−MS, and NMR. The major aldol products observed at high acid concentrations were α, β-unsaturated aldehyde (dimer), trialkyl benzene (trimer) and tetraalkyl cyclo octa-tetra ene (tetramer). The trimer of octanal was formed as trioxane in low sulfuric acid concentration and the possible mechanism accretion reaction pathways of high and low acid concentrations are proposed in this study. A systematic kinetic study of octanal, heptanal, and hexanal in the bulk experiments at 65, 60 and 55 w/v% H2 SO4 at 294K were monitored using gas chromatographic equipped with a flame ionization detector (GC−FID). The rate constants were generally estimated using second-order kinetics and observed to increase as a function of sulfuric acid concentrations and also as the chain length of aliphatic aldehyde increased. The aldol self-reaction in the bulk experiment was too fast at room temperature to be easily measured using a quenching method, therefore, attempts were made to follow the reaction at low temperature (0°C).
Biography:
Supanan Ampawa is studying for a Ph.D. at the Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand. She has received a prestigious scholarship from Science Achievement Scholarship of Thailand since 2010. During her undergraduate study, she investigated the reactivities of allenes and alkenes in Diels–Alder reactions at Mahidol University. After obtaining the B.Sc. degree (Hons), her Ph.D. project involves the development of novel catalysts for sustainable chemistry. In particular, she prepared a series of bis(triazolyl)phenylmethanol–palladium (II) catalysts which were active for crosscoupling reactions in water. This work was published in Chemistry Select journal in 2018. To improve properties and extend the applications of the triazole-based catalysts, she has currently been investigating the synthesis of heterogeneous triazole-based catalysts on silica support and evaluating the effects of ligand structures on catalyst loadings and activities of Pd nanoparticle catalysts fo
Abstract:
A series of triazole-based ligands containing a hydroxyl group, tris(triazolyl) methanol (Htbtm), bis(triazolyl) phenyl methanol (Hbtm), and phenyl(pyridin-2-yl)(triazolyl) methanol (Hpytm), were synthesized and functionalized on 3-chloropropyl silica via deprotonation followed by nucleophilic addition. Subsequent addition of Pd(OAc)2 (OAc = CH3COO‒) onto these supports was carried out. It was found that ligand structures significantly affected Pd loading, which followed the trend: SiO2-tbtm > SiO2-btm ~ SiO2-pytm. Moreover, the influence of different ligand structures on Pd stabilization and catalytic efficiency toward Pd nanoparticle (NP)-catalysed aerobic alcohol oxidation to the corresponding aldehydes was studied. Based on XPS analysis, Pd(II) species were reduced in situ in the presence of alcohols during the first catalytic reactions to generate the active Pd NPs catalysts. Immobilization of Pd NPs on tbtm, btm, pytmmodified silica supports were confirmed by HR-TEM showing average particle diameters of 6.4, 4.8 and 8.5nm, respectively. At 60°C, the Pd NPs stabilized by SiO2-btm exhibited the highest turnover numbers for aerobic oxidation of benzyl alcohol in an ethanol solvent.
Suhair Mansour Jambi
University of Jedahh, Saudi Arabia
Title: Synthesis and characterization of N-eth–N`(4`- methylthiazol) -2ylthiourea
Biography:
Suhair Mansour Jambi has completed her PhD at 2011 from King Abdulaziz university in Saudi Arabia in Jeddah. She is interested in modern technologies in the field of metallic complexes, the structure of metal complexes using modern methods, thiourea complexes and their use in the treatment of some microbes and some diseases such as cancer. She had published more than 10 papers in a reputed journal such as Z.Kristallogr.NCS, Journal of Molecular Liquids, Journal of Molecular Structure & Journal of Sulfur Chemistry. Now she is working at the university of Jeddah.
Abstract:
Thiourea and its derivatives have long been attracting considerable attention due to their biological importance. The facile synthesis of thioureas enabled the preparation of their numerous derivatives, most of which have been evaluated for their biological activities for example herbicidal, insecticidal, antiviral, antifungal, antibacterial. The compound was prepared by boiling under reflux an equal molar ratio of 2-methyl-4-methylthiazole and ethylisothiocyanate for 10 hrs in ethanol as solvent. The reaction product was filtered off, yellow crystals washed with ethanol and recrystallized with ethanol. Yield: 80%; m.p: 233 ÌŠC. Anal. Calc. for C7H11N3S2 (201 g mol-1): C, 41.73; H, 4.97; N, 20.86; S, 31.79 Found: C,42.12; H, 5.05; N, 20.61; S, 31.38. The main IR spectral bands, useful for suggesting the bonding sites of 1- (4-methylthiazol-2-yl)-3 –ethyl thiourea are present. The infrared spectrum of compound, measured in a KBr disc, shows two band at 3435 and 3177 cm-1, assignable to (N1H) and (N2H) respectively, the band at 823 (C=S), 1476.00 (CH3), 680 (C-S-C), 1577; 1535; 1506 C (Tz ring). 1H-NMR â–¡= 1.16 ppm (CH3), â–¡= 2.53 ppm (CH2), â–¡= 2.23 ppm (CH3), â–¡= 6.61 ppm (H-5), â–¡= 9.66 ppm (N2H), â–¡= 11.48 ppm (N1H). 13C-NMR: â–¡= 14.30; 48.20 ppm (ethyl carbons), â–¡= 106.40; 145.90; 161.80 ppm (thiazol carbons), â–¡= 178.50 ppm (C=S), â–¡= 17.00 ppm (CH3). The spectrum of 1- (4-methylthiazol-2-yl)-3 –ethyl thiourea shows a peak at m/z 201 corresponding to a molecular weight of the compound. The molecular compound A loses H2S forming B, loses EtNH2 forming C, loses EtSCN forming D and E.
Issa SAMB
University Alioune Diop of Bambey, Senega
Title: Pyrimidino-pyranoside: A scaffold for drug discovery
Biography:
Issa is currently working as a Senior Lecturer in Organic and Bioorganic Chemistry, Head of the Chemistry Department and Head of the Organic and Therapeutic Chemistry Research Team at the Alioune DIOP Bambey University of Senegal. Issa has done PhD in Molecular Chemistry and Physico-Chemistry from the Henri Poincare University (UHP) in Nancy. He is also an Associate researcher at the Institute of Chemistry of Nice, UMR 7272, CNRS of Nice and the Research Institute of Chemistry Paris, UMR-CNRS 8247, ENSCP, ParisTech. His research activities include Synthesis of new biologically active molecules for the creation of new drugs, Chemistry and Processes for Sustainable Development and Reactions to Atomic Economy and Respectful of the Environment. He has done his Postdoc research at the Institute of Chemistry of Nice (ICN), UMR 7272 CNRS of Nice Cote d’Azur University financed by a French Cooperation Grant in 2018, the Institute of Chemistry and Materials Paris-East (ICMPE), Temporary Attaché of Education and Research (ATER) - IUT Vitry-Creteil of the University of Paris-East Créteil Val de Marne (UPEC )from 2012-2013 and at the Paris Chemistry Research Institute (IRCP) -UMRCNRS 8247 – ENSCP, ParisTech. ANR-CNRS from 2009-2012. issa
Abstract:
The use of carbohydratebased scaffolds for the construction of biologically active compounds is now a well-accepted concept. Our work consists of constructing a bicyclic glucosidic scaffold and studying its potential functionalization for the peptidomimetic design. Starting from methyl α-Dmannopyranoside, we describe rapid access to chiral bicyclic sugar scaffold and its functionalization via Palladiocatalyzed reactions (Suzuki and Stille). The cleavage of benzylidene acetal was carried out by acidic hydrolysis and different alkylation methods with alkyl halides were investigated. This work will provide rapid access to small libraries of new analogs of peptidic receptor ligands (RGD) implied in pathology like cancer and thrombosis.