Benzyl Methyl Research Articles

Commercial Gold(I) and Gold(III) Compounds Supported on Carbon Materials as Greener Catalysts for the Oxidation of Alkanes and Alcohols

AbstractThe front cover artwork for issue 8/2018 stems from a collaboration between the Universities of Porto and Lisbon (Portugal). The image shows two reactions of industrial importance, namely the oxidation of cyclohexane and the oxidation of methyl benzyl alcohol, catalyzed by commercial gold complexes anchored on functionalized carbon nanotubes, in “greener conditions”. See the Full Paper itself at https://doi.org/10.1002/cctc.201701886.

VpStyA1/VpStyA2B of Variovorax paradoxus EPS: An Aryl Alkyl Sulfoxidase Rather than a Styrene Epoxidizing Monooxygenase.

Herein we describe the first representative of an E2-type two-component styrene monooxygenase of proteobacteria. It comprises a single epoxidase protein (VpStyA1) and a two domain protein (VpStyA2B) harboring an epoxidase (A2) and a FAD-reductase (B) domain. It was annotated as VpStyA1/VpStyA2B of Variovorax paradoxus EPS. VpStyA2B serves mainly as NADH:FAD-oxidoreductase. A Km of 33.6 ± 4.0 µM for FAD and a kcat of 22.3 ± 1.1 s−1 were determined and resulted in a catalytic efficiency (kcat Km−1) of 0.64 s−1 μM−1. To investigate its NADH:FAD-oxidoreductase function the linker between A2- and B-domain (AREAV) was mutated. One mutant (AAAAA) showed 18.7-fold higher affinity for FAD (kcat Km−1 of 5.21 s−1 μM−1) while keeping wildtype NADH-affinity and -oxidation activity. Both components, VpStyA2B and VpStyA1, showed monooxygenase activity on styrene of 0.14 U mg−1 and 0.46 U mg−1, as well as on benzyl methyl sulfide of 1.62 U mg−1 and 3.11 U mg−1, respectively. The high sulfoxidase activity was the reason to test several thioanisole-like substrates in biotransformations. VpStyA1 showed high substrate conversions (up to 95% in 2 h) and produced dominantly (S)-enantiomeric sulfoxides of all tested substrates. The AAAAA-mutant showed a 1.6-fold increased monooxygenase activity. In comparison, the GQWCSQY-mutant did neither show monooxygenase nor efficient FAD-reductase activity. Hence, the linker between the two domains of VpStyA2B has effects on the reductase as well as on the monooxygenase performance. Overall, this monooxygenase represents a promising candidate for biocatalyst development and studying natural fusion proteins.

Densely quaternized poly(arylene ether)s with distinct phase separation for highly anion-conductive membranes

To develop high performance anion exchange membranes (AEMs), a novel bisphenol monomer bearing eight benzylmethyl groups at the outer edge of the molecule was synthesized, which after condensation polymerization with various amounts of 4,4′-dihydroxydiphenylsulfone and 4,4′-difluorobenzophenone yielded novel poly(arylene ether)s with densely located benzylmethyl groups. These benzylmethyl groups were then converted to quaternary ammonium groups by radical-initiated bromination and quaternization in tandem, leading to the emergence of densely quaternized poly(arylene ether sulfone)s (QA-PAEs) with controlled ion exchange capacities (IECs) ranging from 1.61 to 2.32 mmol g−1. Both small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) studies revealed distinct phase separation in the QA-PAEs. The QA-PAE-40 with an IEC of 2.32 mmol g−1 exhibited a Br− conductivity of 9.2 mS cm−1 and a SO42− conductivity of 14.0 mS cm−1 at room temperature, much higher than those of a control membrane with a similar IEC but without obvious phase separation. Therefore, phase separation of AEMs was validated to be advantageous for the efficient conducting of anions. The experimental results also showed that the QA-PAEs were promising AEM materials, especially for non-alkaline applications.

Developmental variation in floral volatiles composition of a fragrant orchid Zygopetalum maculatum (Kunth) Garay

Emitted scent volatile profile of an orchid species Zygopetalum maculatum was studied using dynamic headspace sampling technique with four different adsorbent matrices, namely Porapak Type Q polymer (mesh size: 80/100), Tenax (mesh size: 60/80), activated charcoal and graphite. In addition, developmental variations in scent emissions and endogenous volatile levels were also investigated. Gas chromatography-mass spectrometry analysis revealed the presence of 21 volatile compounds in the headspace, which was predominantly enriched with benzenoid compounds. Among these benzenoids, o-diethylbenzene and p-diethylbenzene were the major compounds followed by benzyl acetate and methyl salicylate. Among the phenylpropanoid compounds, 2-phenylethyl acetate was the major volatile. However, as compared to benzenoids, the quantity was much lesser, indicating the inclination of phenylalanine flux towards benzenoid pathway. The outcome of this study has the implications in enhancing fragrance and vase life of orchids of the Sikkim Himalaya region and thus may further help to meet the growing market demand.

Commercial Gold(I) and Gold(III) Compounds Supported on Carbon Materials as Greener Catalysts for the Oxidation of Alkanes and Alcohols

AbstractStrategies are presented for single‐pot efficient oxidative functionalization of cyclohexane and alcohols, under mild conditions, catalysed by Au(I) or Au(III) compounds supported on different carbon materials with three different surface treatments. The obtained materials were tested for the oxidation of cyclohexane under mild conditions (room temperature and atmospheric pressure), using an environmentally friendly oxidant (tert‐butyl hydroperoxide, TBHP, 70 % aqueous solution). All materials were very selective to the production of cyclohexanol and cyclohexanone with no trace of by‐products detected. The catalysts were also tested in the selective oxidation of methyl benzyl alcohol, cyclohexanol, and 2‐octanol with TBHP, under microwave irradiation, to the corresponding aldehydes or ketones. In general, better results are obtained for the heterogenised complexes and that the most efficient support is CNT‐ox‐Na. This is the first report on the oxidation of C−H bonds using the mononuclear gold complexes used; only the oxidation of unsaturated units had been reported previously. The sp3‐C−H activation is much more difficult than the oxidation of unsaturated molecules with molecular oxidants.

Molecular characterization of primary humic-like substances in fine smoke particles by thermochemolysis–gas chromatography–mass spectrometry

In this study, the molecular structures of primary humic-like substances (HULIS) in fine smoke particles emitted from the combustion of biomass materials (including rice straw, corn straw, and pine branches) and coal, and atmospheric HULIS were determined by off-line tetramethylammonium hydroxide thermochemolysis coupled with gas chromatography and mass spectrometry (TMAH-GC/MS). A total of 89 pyrolysates were identified by the thermochemolysis of primary and atmospheric HULIS. The main groups were polysaccharide derivatives, N-containing compounds, lignin derivatives, aromatic acid methyl ester, aliphatic acid methyl ester, and diterpenoid derivatives. Both the type and distribution of pyrolysates among primary HULIS were comparable to those in atmospheric HULIS. This indicates that primary HULIS from combustion processes are important contributors to atmospheric HULIS. Some distinct differences were also observed. The aromatic compounds, including lignin derivatives and aromatic acid methyl ester, were the major pyrolysates (53.0%–84.9%) in all HULIS fractions, suggesting that primary HULIS significantly contributed aromatic structures to atmospheric HULIS. In addition, primary HULIS from biomass burning (BB) contained a relatively high abundance of lignin and polysaccharide derivatives, which is consistent with the large amounts of lignin and cellulose structures contained in biomass materials. Aliphatic acid methyl ester and benzyl methyl ether were prominent pyrolysates in atmospheric HULIS. Moreover, some molecular markers of specific sources were obtained from the thermochemolysis of primary and atmospheric HULIS. For example, polysaccharide derivatives, pyridine and pyrrole derivatives, and lignin derivatives can be used as tracers of fresh HULIS emitted from BB. Diterpenoid derivatives are important markers of HULIS from pine wood combustion sources. Finally, the differences in pyrolysate types and the distributions between primary and atmospheric HULIS suggested that the primary HULIS would undergo many atmospheric processes to reconstruct the macromolecular organic matter in atmospheric aerosols.

Facile Synthesis of Optically Active and Thermoresponsive Star Block Copolymers Carrying Helical Polyisocyanide Arms and Their Thermo-Triggered Chiral Resolution Ability.

A left-handed helical poly(phenyl isocyanide) bearing a norbornene unit and a Pd(II) complex on each terminus was prepared. The norbornene terminus was core cross-linked with a bisnorbornene linker via ring-opening metathesis polymerization (ROMP), yielding a star polymer carrying left-handed helical arms decorated with Pd(II) units at the exterior. The optical activities of the helical arms were maintained after the cross-linking reaction. The Pd(II) units on the surface of the star polymer were chain extended with a new phenyl isocyanide bearing three hydrophilic triethylene glycol monomethyl chains, which afforded an amphiphilic star block copolymer carrying helical arms. Such a star block copolymer showed excellent thermoresponsiveness with the lower critical solution temperature (LCST) around 55 °C. This optically active and thermoresponsive star polymer can enantioselectively capture the S-enantiomer of racemic methyl benzyl alcohol solution at a temperature lower than the LCST and precipitated when the temperature was higher than the LCST, leaving the R-enantiomer in the solution. The enantiomeric excess (ee) of the isolated enantiomer is up to 75%.

Composition and In Vitro Study of Alocasia denudata Engler Stem Juice as a Wound Healing Agent

Event Abstract Back to Event Composition and In Vitro Study of Alocasia denudata Engler Stem Juice as a Wound Healing Agent Siti Aisyah Arshad1, Asmah Hamid1, Farah Wahida Ibrahim1 and Mazlyzam Abdul Latif1* 1 National University of Malaysia, Biomedical Science Programme, Centre for Health & Applied Sciences, Faculty of Health Sciences, Malaysia Background The stem juice of Alocasia denudata Engler is known to possess wound healing properties. This study aimed to analyze the elemental composition and the presence of active compounds in A. denudata stem juice extract and to investigate in vitro wound healing regeneration of A. denudataon human dermal fibroblast cell lines. Methods The proximate element composition was assessed from freeze-dried sample of A. denudata stem juice extracts using scanning electron microscope (SEM). The active compounds of A. denudata stem juice were analyzed using Gas Chromatography-Mass Spectrometry (GCMS) and Liquid Chromatography-Mass Spectrometry (LCMS). The cytotoxicity of the juice was determined using MTT assay and the cell migration rate was determined by using scratch assay. Results Elemental screening showed the presence of oxygen, carbon, potassium, chlorine and sodium and GCMS analysis of the aqueous extract showed the presence of 9-octadecanamide (Z)-, octadecanoic acid-methyl ester, benzyl methyl disulphide as the major components. LCMS analysis revealed the presence of propanoic acid 2-hydroxy-, methyl ester as the major components. All the identified components listed are reported to be conducive for wound healing process. A. denudata extract was proven not cytotoxic to the cells and the highest cell viability was obtained at 62.5 μg/ml. The cells migration towards the wound area also increased compared to the control which shows the highest migration rate at 12-hour. The migration rate was 18 % higher compared to the control suggesting its potential in enhancing wound healing processes. Conclusion A. denudata stem juice extract has the potential to be developed as a wound healing agent. Acknowledgements This work was financially funded by Ministry of Education Fundamental Research Grant Scheme (FRGS/1/2014/SKK01/UKM/02/1) and Biomedical Science Programme, Centre for Health & Applied Sciences, Faculty of Health Sciences, UKM. Keywords: Alocasia denudata Engler, Wound Healing, fibroblast, active compounds, cell migration Conference: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”, Putrajaya, Malaysia, 3 Dec - 5 Feb, 2019. Presentation Type: Poster Presentation Topic: Miscellaneous Citation: Arshad S, Hamid A, Ibrahim F and Abdul Latif M (2019). Composition and In Vitro Study of Alocasia denudata Engler Stem Juice as a Wound Healing Agent. Front. Pharmacol. Conference Abstract: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”. doi: 10.3389/conf.fphar.2018.63.00048 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Oct 2018; Published Online: 17 Jan 2019. * Correspondence: Dr. Mazlyzam Abdul Latif, National University of Malaysia, Biomedical Science Programme, Centre for Health & Applied Sciences, Faculty of Health Sciences, Bangi, Malaysia, mazlyzam@ukm.edu.my Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Siti Aisyah Arshad Asmah Hamid Farah Wahida Ibrahim Mazlyzam Abdul Latif Google Siti Aisyah Arshad Asmah Hamid Farah Wahida Ibrahim Mazlyzam Abdul Latif Google Scholar Siti Aisyah Arshad Asmah Hamid Farah Wahida Ibrahim Mazlyzam Abdul Latif PubMed Siti Aisyah Arshad Asmah Hamid Farah Wahida Ibrahim Mazlyzam Abdul Latif Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Hyperbranched Aliphatic Polyester via Cross-Metathesis Polymerization: Synthesis and Postpolymerization Modification.

A novel postpolymerization modification methodology is demonstrated to achieve selective functionalization of hyperbranched polymer (HBP). Terminal and internal acrylates of HBP derived from cross-metathesis polymerization (CMP) are functionalized in a chemoselective fashion using the thiol-Michael chemistries. Model reactions between different thiols (benzyl mercaptan and methyl thioglycolate) and acrylates (n-hexyl acrylate and ethyl trans-2-decenoate) by using dimethylphenylphosphine or amylamine as the catalyst are investigated to optimize the modification protocol for HBP. High-molecular-weight HBP P0 is generated through CMP of AB2 monomer 2, a compound containing one α-olefin and two acrylate metathetically polymerizable groups. CMP kinetics is monitored by NMR and gel permeation chromatography (GPC). Accordingly, microstructural analysis is conducted in detail, and CMP procedure is optimized. Postpolymerization modification of HBP P0 is performed via two distinguished strategies, namely one-step complete modification and sequential modification, to generate terminally and/or internally functionalized HBPs P1-P3 in a chemoselective fashion by using phosphine-initiated and/or base-catalyzed thiol-Michael chemistries. Finally, thermal stability and glass transition behaviors of HBPs P0-P3 are studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.

Detailed Understanding of the DBU/CO2 Switchable Solvent System for Cellulose Solubilization and Derivatization

In this article, we present an optimization study of the switchable solvent system DBU/CO2 for cellulose solubilization and derivatization via online Fourier transform infrared spectroscopy (FT-IR). By varying temperature, CO2 pressure, and solubilization time, we succeeded in achieving cellulose solubilization within 10–15 min at 30 °C. Compared to traditionally used ionic liquids, the system presented here is cheaper, is easier to recycle, and enables a very fast cellulose solubilization under mild conditions. The efficiency of our optimized mild conditions were further confirmed by X-ray diffraction (XRD) experiments showing the typical transformation from cellulose I to II upon regeneration. In addition, we prove the existence of the in situ formed carbonate anions by trapping them with benzyl bromide or methyl iodide as electrophiles, leading to the successful synthesis of cellulose benzyl carbonate and cellulose methyl carbonate, respectively, under utilization of CO2 as a renewable building block f...

Benzyl methyl ether production from benzyl alcohol and methanol in carbonic water

Synthesis of benzyl methyl ether from benzyl alcohol and methanol in high-temperature carbonic water was studied in a batch reactor. Benzyl methyl ether formation was not observed by reacting benzyl alcohol with only methanol under supercritical conditions at 573K. On the other hand, benzyl methyl ether was formed by the treatment of benzyl alcohol in an aqueous methanol solution at 573K. 12% of benzyl methyl ether yield was obtained in aqueous methanol solution (methanol to water molar ratio of 0.025mol/0.11mol) at 573K in 60min and the yield enhanced to 33% by the addition of 18MPa of carbon dioxide to the aqueous solution. As the etherification is an acid catalyzed reaction, the protons derived from the dissociation of water molecules could be responsible for the etherification of benzyl alcohol in an aqueous methanol solution at 573K. The enhancement of benzyl methyl ether yield by the addition of carbon dioxide in aqueous methanol solution is caused by the increase of the number of protons derived from carbonic acid, which is formed in high-temperature liquid water under high-pressured carbon dioxide.

Assessment of a pretomanid analogue library for African trypanosomiasis: Hit-to-lead studies on 6-substituted 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides

A 900 compound nitroimidazole-based library derived from our pretomanid backup program with TB Alliance was screened for utility against human African trypanosomiasis (HAT) by the Drugs for Neglected Diseases initiative. Potent hits included 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides, which surprisingly displayed good metabolic stability and excellent cell permeability. Following comprehensive mouse pharmacokinetic assessments on four hits and determination of the most active chiral form, a thiazine oxide counterpart of pretomanid (24) was identified as the best lead. With once daily oral dosing, this compound delivered complete cures in an acute infection mouse model of HAT and increased survival times in a stage 2 model, implying the need for more prolonged CNS exposure. In preliminary SAR findings, antitrypanosomal activity was reduced by removal of the benzylic methylene but enhanced through a phenylpyridine-based side chain, providing important direction for future studies.

Reduced 3,4'-bipyrazoles from a simple pyrazole precursor: synthetic sequence, molecular structures and supramolecular assembly.

The reaction of 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and N-benzylmethylamine under microwave irradiation gives 5-[benzyl(methyl)amino]-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, C19H19N3O, (I). Subsequent reactions under basic conditions, between (I) and a range of acetophenones, yield the corresponding chalcones. These undergo cyclocondensation reactions with hydrazine to produce reduced bipyrazoles which can be N-formylated with formic acid or N-acetylated with acetic anhydride. The structures of (I) and of representative examples from this reaction sequence are reported, namely the chalcone (E)-3-{5-[benzyl(methyl)amino]-3-methyl-1-phenyl-1H-pyrazol-4-yl}-1-(4-bromophenyl)prop-2-en-1-one, C27H24BrN3O, (II), the N-formyl derivative (3RS)-5'-[benzyl(methyl)amino]-3'-methyl-1',5-diphenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole]-2-carbaldehyde, C28H27N5O, (III), and the N-acetyl derivative (3RS)-2-acetyl-5'-[benzyl(methyl)amino]-5-(4-methoxyphenyl)-3'-methyl-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole], which crystallizes as the ethanol 0.945-solvate, C30H31N5O2·0.945C2H6O, (IV). There is significant delocalization of charge from the benzyl(methyl)amino substituent onto the carbonyl group in (I), but not in (II). In each of (III) and (IV), the reduced pyrazole ring is modestly puckered into an envelope conformation. The molecules of (I) are linked by a combination of C-H...N and C-H...π(arene) hydrogen bonds to form a simple chain of rings; those of (III) are linked by a combination of C-H...O and C-H...N hydrogen bonds to form sheets of R22(8) and R66(42) rings, and those of (IV) are linked by a combination of O-H...N and C-H...O hydrogen bonds to form a ribbon of edge-fused R24(16) and R44(24) rings.

Copper‐Catalyzed Aerobic Oxygenation of Benzylpyridine N‐Oxides and Subsequent Post‐Functionalization

AbstractA copper‐catalyzed aerobic oxidation of benzylpyridine N‐oxides is reported. The N‐oxide moiety acts as a built‐in activator for the benzylic methylene oxidation, without requirement of additives. Reaction conditions were identified which suppress undesired benzoylpyridine formation via N‐deoxygenation involving intermolecular oxygen transfer. The versatility of the N‐oxide group of the benzoylpyridine N‐oxide reaction products for post‐functionalization of the pyridine ring is demonstrated through efficient C–C, C–N, C–O and C–Cl bond forming procedures, with both nucleophiles and electrophiles. Finally, the applicability of the new synthetic methodology is demonstrated in an alternative route towards the antihistaminic drug Acrivastine via three consecutive N‐oxide activated C–H functionalization processes, starting from picoline N‐oxide.magnified image

Comparison of Orchid Bee (Hymenoptera: Apidae) Species Composition Collected with Four Chemical Attractants

Abstract Orchid bees (Hymenoptera: Apidae: Euglossini) are a diverse and important group of Neotropical pollinators. Numerous chemicals have been used in sampling orchid bees, and species-specific attraction, particularly of males, to these chemicals is well known. However, there have been few studies that have quantified differences in the species composition of orchid bees attracted to particular chemicals. In this study, we compared the abundance and species composition of orchid bees collected with 4 commonly used attractants: benzyl acetate, eucalyptol (or cineole), eugenol, and methyl salicylate. Eucalyptol collected the greatest abundance and species richness of orchid bees. Indicator species analysis revealed that 3 species, Euglossa imperialis Cockerell, Euglossa obtusa Dressler, and Eufriesea mexicana (Mocsary), were significantly associated with eucalyptol, and 1, Eulaema marcii Nemesio, with benzyl acetate. The multi-response permutation procedure revealed relatively large differences in speci...

Stereoselective Postassembly CH Oxidation of Self-Assembled Metal-Ligand Cage Complexes.

Self-assembled Fe-iminopyridine cage complexes containing doubly benzylic methylene units such as fluorene and xanthene can be selectively oxidized at the ligand backbone with tBuOOH, with no competitive oxidation observed at the metal centers. The self-assembled cage structure controls the reaction outcome, yielding oxidation products that are favored by the assembly, not by the reactants or functional groups. Whereas uncomplexed xanthene and fluorene control ligands are solely oxidized to the ketone equivalents with tBuOOH, the unfavorability of the self-assembled ketone cages forces the reaction to form the tbutyl peroxide and alcohol-containing oxidation products, respectively. In addition, the oxidation is diastereoselective, with only single isomers of the cage assemblies formed, despite the presence of as many as 10 stereocenters in the final product. The self-assembled structures exploit self-complementary hydrogen bonding and geometrical constraints to direct the postassembly reactions to outcomes not observed in free solution. This selectivity is reminiscent of the fine control of post-translational modification seen in biomacromolecules.

Study on the Alkylation Reactions of N(7)-Unsubstituted 1,3-Diazaoxindoles.

The chemistry of the 5,7-dihydro-6H-pyrrolo[2,3-d]pyrimidin-6-one (1,3-diazaoxindole) compound family, possessing a drug-like scaffold, is unexplored. In this study, the alkylation reactions of N(7)-unsubstituted 5-isopropyl-1,3-diazaoxindoles bearing various substituents at the C(2) position have been investigated. The starting compounds were synthesized from the C(5)-unsubstituted parent compounds by condensation with acetone and subsequent catalytic reduction of the 5-isopropylidene moiety. Alkylation of the thus obtained 5-isopropyl derivatives with methyl iodide or benzyl bromide in the presence of a large excess of sodium hydroxide led to 5,7-disubstituted derivatives. Use of butyllithium as the base rendered alkylation in the C(5) position possible with reasonable selectivity, without affecting the N(7) atom. During the study on the alkylation reactions, some interesting by-products were also isolated and characterized.

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

ABSTRACTThe correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.

Cross-Dehydrogenative Coupling of Heterocyclic Scaffolds with Unfunctionalized Aroyl Surrogates by Palladium(II) Catalyzed C(sp2)-H Aroylation through Organocatalytic Dioxygen Activation.

Cross-dehydrogenative coupling of biorelevant heterocyclic scaffolds with arylmethanes for aroylation during Pd(II)-catalyzed C(sp2)-H activation has been achieved through dioxygen activation by NHPI. Mass spectrometry and 1H NMR based kinetic isotope effect studies revealed C-H bond activation as the rate-determining step. Radical scavenging experiments indicated a radical pathway. The 1H NMR of an aliquot of reaction mixture and in situ trapping with 2-aminothiophenol revealed the formation of aldehyde during aerobic oxidation of the arylmethanes. The reaction has broad scope for different variations of the aroyl source and the directing group that includes benzothiazole, benzooxazole, pyridine, quinoxaline, pyrimidine, and azoarene. The benzylic methylene moiety was found to be the source of the aroyl carbon with the benzyl ether moiety being the most preferred followed by the carbonyl group of aryl aldehyde and the aryl methane. However, the ease of availability of aryl methanes makes them the most attractive as an aroyl source. A time dependent selective mono- and bis-aroylation can be achieved. The 1,3-diarylpyrimidines exhibited regioselective aroylation of the 2-phenyl moiety irrespective of the absence or presence of any substitutent (electron withdrawing or electron donating) in the 3-phenyl moiety. For unsymmetrical azoarenes, selective aroylation took place in the phenyl moiety bearing the substituent.

Chemometrics-assisted chromatographic fingerprinting: An illicit methamphetamine case study.

The volatile chemical constituents in complex mixtures can be analyzed using gas chromatography with mass spectrometry. This analysis allows the tentative identification of diverse impurities of an illicit methamphetamine sample. The acquired two-dimensional data of liquid-liquid extraction was resolved by multivariate curve resolution alternating curve resolution to elucidate the embedded peaks effectively. This is the first report on the application of a curve resolution approach for chromatogram fingerprinting to identify particularly the embedded impurities of a drug of abuse. Indeed, the strong and broad peak of methamphetamine makes identifying the underlying peaks problematic and even impossible. Mathematical separation instead of conventional chromatographic approaches was performed in a way that trace components embedded in methamphetamine peak were successfully resolved. Comprehensive analysis of the chromatogram, using multivariate curve resolution, resulted in elution profiles and mass spectra for each pure compound. Impurities such as benzaldehyde, benzyl alcohol, benzene, propenyl methyl ketone, benzyl methyl ketone, amphetamine, N-benzyl-2-methylaziridine, phenethylamine, N,N,α-trimethylamine, phenethylamine, N,α,α-trimethylmethamphetamine, N-acetylmethamphetamine, N-formylmethamphetamine, and other chemicals were identified. A route-specific impurity, N-benzyl-2-methylaziridine, indicating a synthesis route based on ephedrine/pseudoephedrine was identified. Moreover, this is the first report on the detection of impurities such as phenethylamine, N,α,α-trimethylamine (a structurally related impurity), and clonitazene (as an adulterant) in an illicit methamphetamine sample.