Alkoxy Moiety Research Articles

Synthesis and Evaluation of Imidazole Derivatives Bearing Imidazo[2,1-b] [1,3,4]thiadiazole Moiety as Antibacterial Agents.

Drug-resistant infections kill hundreds of thousands of people globally every year. In previous work, we found that tri-methoxy- and pyridine-substituted imidazoles show strong antibacterial activities. The aim of this work was to investigate the antibacterial activities and bacterial resistances of imidazoles bearing an aromatic heterocyclic, alkoxy, or polycyclic moiety on the central ring. Three series of 2-cyclopropyl-5-(5-(6-methylpyridin-2-yl)-2-substituted-1H-imidazol-4- yl)-6-phenylimidazo[2,1-b][1,3,4]thiadiazoles (13a-e, 14a-d, and 15a-f) were synthesized and their antibacterial activity was evaluated. The structures were confirmed by their 1H NMR, 13C NMR, and HRMS spectra. All the synthesized compounds were screened against Gram-positive, Gramnegative, and multidrug-resistant bacterial strains. More than half of the compounds showed moderate or strong antibacterial activity. Among them, compound 13e (MICs = 1-4 μg/mL) showed the strongest activity against Gram-positive and drug-resistant bacteria as well as high selectivity against Gram-negative bacteria. Furthermore, it showed no cytotoxicity against HepG2 cells, even at 100 μM, and no hemolysis at 20 μM. These results indicate that compound 13e is excellent candicate for further study as a potential antibacterial agent.

Diversity-oriented synthesis of indole-fused scaffolds and bis(indolyl)methane from tosyl-protected tryptamine.

An efficient, diversity-oriented synthesis of indole-1,2-fused 1,4-benzodiazepines, tetrahydro-β-carbolines, and 2,2'-bis(indolyl)methanes was established starting from tosyl-protected tryptamine. These diverse privileged skeletons were controllably constructed by adjusting different hydride donors and Brønsted acids. A variety of indole-1,2-fused 1,4-benzodiazepines were facilely accessed using benzaldehydes bearing cyclic amines as hydride donors via a cascade N-alkylation/dehydration/[1,5]-hydride transfer/Friedel-Crafts alkylation sequence. The reaction site could be switched when benzaldehydes bearing an alkoxy moiety as hydride donors were used for the generation of tetrahydro-β-carbolines. On the other hand, the switchable synthesis of 2,2'-bis(indolyl)methanes could be achieved as well by applying p-TsOH·H2O as a catalyst. The reactions feature mild conditions, simple and practical operation, excellent efficiency and the use of EtOH as a green solvent. Using the concept of diversity-oriented, reagent-based synthesis, the inexpensive feedstock tryptamine was efficiently converted to three different types of privileged scaffolds, which facilitates rapid compound library synthesis for accelerating drug discovery.

Synthesis of Cationic Sandwich-type Ruthenium Complexes with η6-Arene Ligands Bearing Long Alkyl Chains and Their Behavior in Water

Abstract Novel sandwich-type ruthenium complexes [Ru(η6-arene)(p-cymene)](BF4)2, in which the η6-arene ligands have long alkyl chains, were prepared. These complexes were dispersed in water to form corresponding micelles. Alkoxy moieties on the η6-arene ligands were reacted with OH− to afford the corresponding phenolic species. Thus, [Ru(p-undecyloxyanisole)(p-cymene)]2+ was converted to [Ru(η6-p-methoxyphenolate)(p-cymene)]+ through the unexpected demethylation by treatment with Na2CO3 with the micelle remaining. The micelle collapsed when similar ruthenium complex bearing dodecyl 2-(4-methoxyphenoxy)acetate as an arene ligand was treated with Na2CO3 aq.

Asymmetric Michael Reaction of Malononitrile and α,β-Unsaturated Aldehydes Catalyzed by Diarylprolinol Silyl Ether

AbstractAn asymmetric Michael reaction of malononitrile and α,β-unsaturated aldehydes catalyzed by a diarylprolinol silyl ether was developed. Michael products were obtained in good yields and with excellent enantioselectivities without the formation of overreaction products. As a malononitrile moiety can be transformed into an alkoxy or amino carbonyl moiety by oxidative transformation, α-chiral esters or amides with all-carbon quaternary centers can be synthesized with excellent enantioselectivities.

Recent Achievements on Functionalization within closo‐Decahydrodecaborate [B10H10]2− Clusters

AbstractCloso‐decahydrodecaborate anion, [B10H10]2−, is one of the most notable clusters in the family of hydroborates, partly attributed to its unique electronic structure and its thermal and chemical stability. The major challenge in the development of [B10H10]2− chemistry resides in its functionalization via the activation of exo‐polyhedral B−H bonds to B−L bonds to generate attractive molecular construction modules or ‘archetypes’ of useful applications. To date, the closo‐[B10H10]2− cage has been functionalized with a wide range of functional groups ‐L such as halogens, amines, thiols, alkoxy, hydroxyl and multifunctional moieties to yield mono‐ or poly‐substituted borate derivatives. In this review, we present the recent trends in the chemistry of closo‐decaborate with focus on the substitution reactions of hydrogen atoms by various entities.

Activated Hoveyda‐Grubbs Olefin Metathesis Catalysts Derived from a Large Scale Produced Pharmaceutical Intermediate – Sildenafil Aldehyde

AbstractTwo EWG‐activated Hoveyda‐Grubbs‐type ruthenium complexes (Sil‐II and Sil‐II’) were obtained, characterized, and screened in a set of olefin metathesis reactions. These catalysts were conveniently synthesized from a commercially available pharmaceutical building block – Sildenafil aldehyde – in two steps only. Stability and catalytic activity tests disclosed that the bulkier NHC‐ligand bearing catalyst Sil‐II’ is visibly more stable and productive than its smaller NHC‐analogue Sil‐II. Good application profile of catalyst Sil‐II’ was confirmed in a set of diverse metathesis reactions including ring‐closing metathesis (RCM) and cross‐metathesis (CM) of complex polyfunctional substrates of medicinal chemistry interest, including a challenging macrocyclization of the Pacritinib precursor. Compatibility of the new catalyst with various green solvents was checked and metathesis of Sildenafil and Tadalafil‐based substrates was successfully conducted in acetone. The mechanism of Sil‐II’ initiation has been investigated through kinetic experiments unveiling that the decrease of the steric hindrance of the chelating alkoxy moiety (from iPrO to EtO) favors the interchange initiation pathway over the typical dissociation pathway for other popular 2nd generation Hoveyda‐Grubbs catalysts.magnified image

Poly(ionic liquid)s Containing Alkoxy Chains and Bis(trifluoromethanesulfonyl)imide Anions as Highly Adhesive Materials.

Adhesive materials have wide applications in diverse fields, but the development of a novel and multipurpose adhesive is a great challenge. This study demonstrates that conventional poly(ionic liquid)s (PILs) can be designed as highly efficient adhesives by simply introducing alkoxy moieties into the cationic backbone of PILs containing bis(trifluoromethanesulfonimide) (TFSI- ) anions. The incorporated flexible alkoxy chain not only reduces the glass transition temperature of PILs but also endows these materials with strong hydrogen bonding interactions, which, together with the unique electrostatic interaction of the PILs, simultaneously contributes to a high cohesive energy and interfacial adhesive energy. Consequently, these alkoxy PILs are highly adhesive on various substrates such as glass, ceramic, stainless steel, aluminum, and polymers, in contrast to the nonadhesive behavior of conventional PILs. Photosensitive or electronically conductive composite adhesives are fabricated by virtue of the compatibility between ionic liquids and carbon nanotubes or silver nanofibers. Interestingly, the PIL-2-TFSI adhesive possesses a unique and reversible response to electric fields and achieves up to 35% improvement in adhesive strength.

One-step direct oxidation of fullerene-fused alkoxy ethers to ketones for evaporable fullerene derivatives

Ketones are widely applied moieties in designing functional materials and are commonly obtained by oxidation of alcohols. However, when alcohols are protected/functionalized, the direct oxidation strategies are substantially curbed. Here we show a highly efficient copper bromide promoted one-step direct oxidation of benzylic ethers to ketones with the aid of a fullerene pendant. Mechanistic studies unveil that fullerene can serve as an electron pool proceeding the one-step oxidation of alkoxy group to ketone. In the absence of the fullerene pendant, the unreachable activation energy threshold hampers the direct oxidation of the alkoxy group. In the presence of the fullerene pendant, generated fullerene radical cation can activate the neighbour C–H bond of the alkoxy moiety, allowing a favourable energy barrier for initiating the direct oxidation. The produced fullerene-fused ketone possesses high thermal stability, affording the pin-hole free and amorphous electron-transport layer with a high electron-transport mobility.

Solid-Phase Microcontact Printing for Precise Patterning of Rough Surfaces: Using Polymer-Tethered Elastomeric Stamps for the Transfer of Reactive Silanes.

We present a microcontact printing (μCP) routine suitable to introduce defined (sub-) microscale patterns on surface substrates exhibiting a high capillary activity and receptive to a silane-based chemistry. This is achieved by transferring functional trivalent alkoxysilanes, such as (3-aminopropyl)-triethoxysilane (APTES) as a low-molecular weight ink via reversible covalent attachment to polymer brushes grafted from elastomeric polydimethylsiloxane (PDMS) stamps. The brushes consist of poly{N-[tris(hydroxymethyl)-methyl]acrylamide} (PTrisAAm) synthesized by reversible addition–fragmentation chain-transfer (RAFT)-polymerization and used for immobilization of the alkoxysilane-based ink by substituting the alkoxy moieties with polymer-bound hydroxyl groups. Upon physical contact of the silane-carrying polymers with surfaces, the conjugated silane transfers to the substrate, thus completely suppressing ink-flow and, in turn, maximizing printing accuracy even for otherwise not addressable substrate topographies. We provide a concisely conducted investigation on polymer brush formation using atomic force microscopy (AFM) and ellipsometry as well as ink immobilization utilizing two-dimensional proton nuclear Overhauser enhancement spectroscopy (1H–1H-NOESY-NMR). We analyze the μCP process by printing onto Si-wafers and show how even distinctively rough surfaces can be addressed, which otherwise represent particularly challenging substrates.

Synthesis and characterization of liquid crystal compounds based on azo group

Abstract A calamitic non-symmetric liquid crystalline dimers consists of azo benzene containing azobenzene moiety was synthesized and analyzed. Nine distinguishable alkoxy moieties differ within a count of carbon-based particles and therefore methylene components seven and eight were produced and characterized via spectrometric techniques. All the produced particles displayed enantiotropic fluid quartz stage by overall dimers showing nematic phase whereas the higher homologues showed nematic and smectic phases. The conversion temperature and stage behavior was calculated by Differential Scanning Calorimeter and Polarizing Optic Microscope.

Electrosynthesis 2.0 in 1,1,1,3,3,3‐Hexafluoroisopropanol/Amine Mixtures

AbstractThe intention of this review is to highlight the innovative electrolyte combination of 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) with tertiary nitrogen bases in electro‐organic synthesis. This easy applicable and promising mixture is not yet well established in electro‐organic synthesis, but expands the various possibilities in the latter. Combinations of fluorinated alcohols with nitrogen bases form highly conductive electrolyte systems, which can be evaporated completely. Consequently, no additional supporting electrolyte is required and work‐up procedures are tremendously simplified. With this electrolyte mixture carbon‐carbon homo‐ and cross‐coupling reactions of arenes and phenols have been established with substrates that have not been previously susceptible to the anodic dehydrogenative coupling reaction. The intermediate installation of highly fluorinated alkoxy moieties can be exploited for subsequent conversions as well as various benzylic functionalization, including asymmetric transformations. These transformations show unique selectivity and functional group tolerance making them highly applicable to the synthesis of sophisticated structural motifs, including natural products.

Metal-Free Oxidative Esterification of Ketones and Potassium Xanthates: Selective Synthesis of α-Ketoesters and Esters.

A novel and efficient oxidative esterification for the selective synthesis of α-ketoesters and esters has been developed under metal-free conditions. In the protocol, various α-ketoesters and esters are available in high yields from commercially available ketones and potassium xanthates. Mechanistic studies have proven that potassium xanthate not only promotes oxidative esterification but also provides an alkoxy moiety for the reaction, which involves the cleavage and reconstruction of C-O bonds.

Design, Synthesis and Biological Activity of Pyrimidyl-Salicylate Derivatives Containing Alkoxy Moiety

Design, Synthesis and Biological Activity of Pyrimidyl-Salicylate Derivatives Containing Alkoxy Moiety

Programming the Knowledge: A Trial QSAR Study Towards the Stability of Dialkoxy Benzene Based Catholyte Molecules for Nonaqueous Redox Flow Batteries

Programming the knowledge: A trial QSAR study towards the stability of dialkoxy benzene based catholyte molecules for nonaqueous redox flow batteries Lu Zhang1, Jingjing Zhang1, Benjamin Silcox3, Illya A. Shkrob1, Rajeev S. Assary2, Lei Cheng2, Levi Thompson4 1Chemical Sciences and Engineering Division, 2Material Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, United States 3Chemical Engineering, University of Michigan, 500 S State St, Ann Arbor, MI 48109, United States 4Department of Chemical and Biomolecular Engineering, University of Delaware,Newark, DE 19716, Unite States The stability of redox active molecules is a paramount property that dramatically affects the cycling performance in redox flow batteries. Computationally, it requires huge amount of resource to exhaustively iterate all the possible degradation pathways in order to estimate the stability of active species, such as radical cations.1 QSAR, or quantitative structure–activity relationship, provides an interesting approach to correlate chemical structures and properties based on the idea of property changes are all coming from structure modifications. While this approach simplified the insightful analysis of the detailed mechanism, it becomes particular useful to simulate or even predict complex properties, such as the stability of redox molecules. In this talk, we developed a series of dialkoxy benzene based catholyte molecules that are of potential use to nonaqueous redox flow batteries and systematically changed their substitutions on the alkoxy moieties. Then their electrochemical/chemical properties, including redox potential, charged state stability (reflected by EPR life time), and even cycling numbers, have been characterized and analyzed. Importantly, a number of descriptors have been identified based on our long accumulated knowledge regarding stability of the charged radical cations. Finally, a linear regression model was established using those descriptors to simulate the EPR life time, and even cycling numbers and the resulted fittings delivered quite satisfactory correlation between the selected descriptors and properties. While this is only a trial study based on a small set of molecules, the QSAR approach proves to be useful in understanding complex properties for redox active molecules, which could stimulate further understanding and development of such promising materials. Assary, R. S.; Zhang, L.; Huang, J.; Curtiss, L. A., Molecular Level Understanding of the Factors Affecting the Stability of Dimethoxy Benzene Catholyte Candidates from First-Principles Investigations. The Journal of Physical Chemistry C 2016, 120 (27), 14531-14538.

Influence of Alkoxy Chain Length on the Properties of Two-Dimensionally Expanded Azulene-Core-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells.

A series of two-dimensionally expanded azulene-core-based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen-bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n-butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n-butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro-OMeTAD-based PSCs (spiro-OMeTAD=2,2',7,7'-tetrakis[N,N-bis(p-methoxyphenyl)amino]-9,9'-spirobifluorene).

From a (Pseudo) Aluminum Sesquihalide Al2(Et)3(ORF)3 to Me3Si–Cl–Al(ORF)3 (RF = C(CF3)3)

By reaction of AlEt3 with less than 3 equiv of HORF (RF = C(CF3)3) the ethylaluminum sesquialkoxide (Et)2Al(μ-ORF)2Al(Et)(ORF) (1a; NMR, XRD) can be obtained. As a univalent electronegative residue, the perfluorinated alkoxy moieties can be seen as pseudohalides. In this respect, 1a represents the closest approximation to the hitherto unknown crystal structure of the alkylaluminum sesquihalide Al2R3X3. By further reaction of 1a with HORF, the Lewis superacid Al(ORF)3 is formed, which reacts with Me3SiCl to give Me3Si–Cl–Al(ORF)3 (2a; NMR, XRD, IR, Raman). 2a can be used for further reactions as prepared but slowly decomposes at ca. 0 °C to give the known Me3Si–F–Al(ORF)3 (2b) and several byproducts. The observed decomposition products, combined with quantum chemical calculations, provide evidence for an even higher silylating potential of 2a over that of 2b.

Bidirectional metal‐free ROMP from difunctional organic initiators

Bidirectional metal‐free ROMP from difunctional organic initiators

Density functional theory design D-D-A type small molecule with 1.03 eV narrow band gap: effect of electron donor unit for organic photovoltaic solar cell

ABSTRACTSix new low-band-gap copolymers of donor–donor–acceptor (D-D-A) architecture have been designed using density functional theory and time-dependent density functional theory methods in order to use them in organic photovoltaic cell (OPVC). Phenanthro[3,4-d:9,10-d′]bis([1,2,3]thiadiazole)-10,12-dicarbonitrile moiety has been used as an acceptor for all compounds. We insert benzo[1,2-b:4,5-b′]dithiophene and N,N-diphenylbenzo[1,2-b:4,5-b′]dithiophen-2-amine units as donor to complete designing of copolymers. In order to tuning the optical and electronic properties, we have modified the donor unit by substituted with amine, methoxyamine, N-methylenethiophen-2-amine, methoxy, alkoxy moieties. The band gap (Eg), HOMO and LUMO values and plots, open circuit voltage (VOC) as well as optical properties have been analysed for designed copolymers. The optimised copolymers exhibit low-band-gap lying in the range of 1.03–2.24 eV. DPTD-6 copolymer presents the optimal properties to be used as an active layer due to its low Eg (1.03 eV) and a moderate VOC (0.56 eV). Thus, OPVC based on this copolymer in bulk-heterojunction composites with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an acceptor has been modelled. Eg and VOC values of composite material DPTD-6:PCBM are found as 1.32 and 0.65 eV, respectively. A model band diagram has been established for OPVC, simulating the energy transfer between active layers.

Supported Pt-Re catalysts for the selective hydrogenation of methyl and ethyl esters to alcohols

The effect of Re-addition to Pt/TiO2 catalysts for the hydrogenation of carboxylic acids and esters to their corresponding alcohols was investigated. The highest catalytic activity was observed for the materials with Pt:Re molar ratio of 1:2, which allowed for a complete conversion of hexanoic acid under mild conditions. The hydrogenation of esters over the same catalysts was much more difficult. The reactions showed only moderate alcohol yields which also depended strongly on the alkoxy moiety of the ester substrate. The highest yield of ca. 25% was achieved by the hydrogenation of ethyl hexanoate. Conversion of methyl hexanoate was much less efficient. This was attributed to the inhibiting effect of methanol by-product. In situ FTIR spectroscopy suggests that the decarbonylation of methanol and the resulting CO poisoning of the catalyst surface in the course of the reaction is the most likely cause of the low activity of Pt and Pt-Re/TiO2 towards methyl ester hydrogenation.

Synthesis and Hydrolysis of Alkoxy(aminoalkyl)diorganylsilanes of the Formula Type R2(RO)Si(CH2)nNH2 (R = Alkyl, n = 1–3): A Systematic Experimental and Computational Study

AbstractAlkoxy(aminoalkyl)silanes are important precursors for the formation of amino‐functionalized polysiloxanes, which are used in many technical applications. To better understand the mechanism of the hydrolytic cleavage of the Si–alkoxy moiety of alkoxy(aminoalkyl)silanes (an important key step in the formation of amino‐functionalized polysiloxanes), a systematic experimental and computational study on the hydrolysis of alkoxy(aminoalkyl)diorganylsilanes of the formula type R2(RO)Si(CH2)nNH2 (R = alkyl, n = 1–3) was conducted. For reasons of comparison, silanes of the formula types R2(RO)SiC(H)MeCH2NH2 and R2(RO)Si(CH2)nX [R = alkyl; n = 1–3; X = N(H)Me, NMe2, piperidino, NMe3+I–, N(H)COOMe, N(Me)COOMe] and compounds Me2(MeO)Si(CH2)6Me and Me2(MeO)Si(CH2)6NH2 were included in this study. For this purpose, the various silanes were synthesized and studied for their hydrolysis kinetics in CD3CN/D2O under acidic and basic conditions by using 1H NMR spectroscopy as the analytic tool. These experimental investigations were complemented by computational studies (calculation of proton affinities, reaction barriers, and energies relative to reactants of intermediate transition complexes). The different hydrolysis reactivities observed are the result of a number of parameters, such as electronic and steric effects, the strong impact of the pD value, and intramolecular N–H···O hydrogen bonds between the protonated amino group and the alkoxy leaving group. This comprehensive study provided deep insight into the mechanism of hydrolysis of analogous α‐, β‐, and γ‐amino‐functionalized alkoxy(aminoalkyl)diorganylsilanes of the formula type R2(RO)Si(CH2)nNH2 (R = organyl, n = 1–3) and a series of related α/β/γ analogues with other nitrogen‐based functional groups.