Multiple Alkyl Research Articles

Luminescent columnar liquid crystals based on AIE tetraphenylethylene with hydrazone groups bearing multiple alkyl chains

A series of novel tetraphenylethylene aromatic acylhydrazone derivatives 11, 12 and 13 with 4, 8 or 12 alkyl chains were designed and synthesized in yields of 82–85%. Studies on the mesomorphic properties suggested the ordered hexagonal columnar mesophase for compounds 11, 12 and 13. The increase in the number of alkyl chains was favourable for decreasing the phase-transition temperatures and extending the mesophase temperature range. Further, samples 11, 12 and 13 presented an excellent AIE effect. The fluorescence intensities increased by 70, 84 and 43 times for samples 11, 12 and 13, respectively. The absolute fluorescence quantum yields were 18.7%, 27.4% and 23.8% in solid films at room temperature and 6.7%, 24.2% and 17.3% in the mesophase. These results suggested that the number of alkyl chains greatly influenced the fluorescence emission and sample 12 with 8 alkyl chains exhibited the strongest fluorescence emission. Sample 12 also displayed the electroluminescence performance on OLED device.

The Xanthate Route to Ketones: When the Radical Is Better than the Enolate.

The alkylation of enolates is one of the backbones of ketone chemistry, yet in practice it suffers from numerous limitations due to problems of regiochemistry (including O- versus C-alkylation), multiple alkylations, self-condensation, competing elimination, and incompatibility with many polar groups that have to be protected. Over the years, various solutions have been devised to overcome these difficulties, such as the employment of auxiliary ester or sulfone groups to modify the p Ka of the enolizable hydrogens, the passage by the corresponding hydrazones, the use of transition-metal-catalyzed redox systems to formally alkylate ketones with alcohols, etc. Most of these hurdles disappear upon switching to α-ketonyl radicals. Radicals are tolerant of most polar functions, and radical additions to flat sp2 centers are generally easier to accomplish than enolate substitution at tetrahedral sp3 carbons. The main stumbling block, however, has been a lack of generally applicable methods for the generation and intermolecular capture of α-ketonyl radicals. We have found over the past years that the degenerative exchange of xanthates represents in many ways an ideal solution to this problem. It overcomes essentially all of the difficulties faced by other radical processes because of its unique ability to reversibly store reactive radicals in a dormant, nonreactive form. The lifetime of the radicals can therefore be significantly enhanced, even in the concentrated medium needed for bimolecular additions, while at the same time regulating their absolute and relative concentrations. The ability to perform intermolecular additions to highly functionalized alkene partners opens up numerous possibilities for rapid and convergent access to complex structures. Of particular importance is the elaboration of ketones that are prone to self-condensation, such trifluoroacetone, and of base-sensitive ketones, such as chloro- and dichloroacetone, since the products can be used for the synthesis of a myriad fluorinated and heteroaromatic compounds of relevance to medicinal chemistry and agrochemistry. The formal distal dialkylation of ketones, also of utmost synthetic interest, is readily accomplished, allowing convenient access to a wide array of useful ketone building blocks. Cascade processes can be implemented and, in alliance with powerful classical reactions (aldol, alkylative Birch reductions, etc.), furnish a quick route to complex polycyclic scaffolds. Furthermore, the presence of the xanthate group in the adducts can be exploited to obtain a variety of arenes and heteroarenes, such as pyrroles, thiophenes, naphthalenes, and pyridines, as well as enones, dienes, and cyclopropanes. Last but not least, the reagents and most of the starting materials are exceedingly cheap, and the reactions are safe and easy to scale up.

Perylene liquid crystals with multiple alkyl chains: investigation of the influence of peripheral alkyl chain number on mesomorphic and photophysical properties

Novel perylene liquid crystals with 2, 4 and 6 peripheral alkyl chains or 6, 8 and 10 peripheral alkyl chains at both the imide and bay-positions were investigated.

Evaluating solid phase (micro-) extraction tools to analyze freely ionizable and permanently charged cationic surfactants

Working with and analysis of cationic surfactants can be problematic since aqueous concentrations are difficult to control, both when taking environmental aqueous samples as well as performing laboratory work with spiked concentrations. For a selection of 32 amine based cationic surfactants (including C8- to C18-alkylamines, C14-dialkyldimethylammonium, C8-tetraalkylammonium, benzalkonium and pyridinium compounds), the extraction from aqueous samples was studied in detail. Aqueous concentrations were determined using solid phase extraction (SPE; 3 mL/60 mg Oasis WCX-SPE cartridges) with recoveries of ≥80% for 30 compounds, and ≥90% for 16 compounds. Sorption to glassware was evaluated in 120 mL flasks, 40 mL vials and 1.5 mL autosampler vials, using 15 mM NaCl, where the glass binding of simple primary amines and quaternary ammonium compounds increased with alkyl chain length. Sorption to the outside of pipette tips (≤20% of total amount in solution) when sampling aqueous solutions may interfere with accurate measurements. Polyacrylate solid phase microextraction (PA-SPME) fibers with two coating thicknesses (7 and 35 μm) were tested as potential extraction devices. The uptake kinetics, pH-dependence and influence of ionic strength on sorption to PA fibers were studied. Changing medium from 100 mM Na+ to 10 mM Ca2+ decreases Kfw with one order of magnitude. Results indicate that for PA-SPME neutral amines are absorbed rather than adsorbed, although the exact sorption mechanism remains to be elucidated. Further research remains necessary to establish a definitive applicability domain for PA-SPME. However, results indicate that alkyl chain lengths ≥14 carbon atoms and multiple alkyl chains become problematic. A calibration curve should always be measured together with the samples. In conclusion, it seems that for amine based surfactants PA-SPME does not provide the reliability and reproducibility necessary for precise sorption experiments, specifically for alkyl chain lengths beyond 12 carbon atoms.

DNA Condensation Induced by a Star-Shaped Hexameric Cationic Surfactant.

The interactions between a star-shaped hexameric cationic quaternary ammonium surfactant PAHB and calf thymus DNA and induced DNA condensation were investigated by ζ-potential, dynamic light scattering, atomic force microscopy, isothermal titration calorimetry, ethidium bromide exclusion assay, circular dichroism, and cytotoxicity assay. With the addition of PAHB, long extended DNA molecules exhibit successive conformational transitions from elongated coil to a partially condensed cluster-like aggregate, to a globules-on-a-string structure, and then to a fully condensed globule until the saturation point of interaction between PAHB and DNA, which is slightly above their charge neutralization point. The efficient condensation is mainly produced by the strong attractive electrostatic interaction between the multiple positively charged headgroups of PAHB and negatively charged phosphate groups of DNA, and the hydrophobic interaction among the multiple alkyl chains of PAHB. Moreover the transition of the DNA conformation is also affected by the transitions of PAHB molecular conformation from star-shaped to claw-like and pyramid-like. Although the DNA conformation is significantly changed by PAHB, the DNA secondary structure does not display obvious variations, and the PAHB/DNA mixture does not show cytotoxicity when DNA is partially condensed. These results indicate that star-shaped oligomeric cationic surfactant is a potential condensing agent for gene transfection.

Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines.

The intermolecular hydroamination of unactivated alkenes with simple dialkyl amines remains an unsolved problem in organic synthesis. We report a catalytic protocol for efficient additions of cyclic and acyclic secondary alkyl amines to a wide range of alkyl olefins with complete anti-Markovnikov regioselectivity. In this process, carbon-nitrogen bond formation proceeds through a key aminium radical cation intermediate that is generated via electron transfer between an excited-state iridium photocatalyst and an amine substrate. These reactions are redox-neutral and completely atom-economical, exhibit broad functional group tolerance, and occur readily at room temperature under visible light irradiation. Certain tertiary amine products generated through this method are formally endergonic relative to their constituent olefin and amine starting materials and thus are not accessible via direct coupling with conventional ground-state catalysts.

Which Molecular Features Affect the Intrinsic Hepatic Clearance Rate of Ionizable Organic Chemicals in Fish?

Greater knowledge of biotransformation rates for ionizable organic compounds (IOCs) in fish is required to properly assess the bioaccumulation potential of many environmentally relevant contaminants. In this study, we measured in vitro hepatic clearance rates for 50 IOCs using a pooled batch of liver S9 fractions isolated from rainbow trout (Oncorhynchus mykiss). The IOCs included four types of strongly ionized acids (carboxylates, phenolates, sulfonates, and sulfates), three types of strongly ionized bases (primary, secondary, tertiary amines), and a pair of quaternary ammonium compounds (QACs). Included in this test set were several surfactants and a series of beta-blockers. For linear alkyl chain IOC analogues, biotransformation enzymes appeared to act directly on the charged terminal group, with the highest clearance rates for tertiary amines and sulfates and no clearance of QACs. Clearance rates for C12-IOCs were higher than those for C8-IOC analogues. Several analogue series with multiple alkyl chains, branched alkyl chains, aromatic rings, and nonaromatic rings were evaluated. The likelihood of multiple reaction pathways made it difficult to relate all differences in clearance to specific molecular features the tested IOCs. Future analysis of primary metabolites in the S9 assay is recommended to further elucidate biotransformation pathways for IOCs in fish.

ChemInform Abstract: Regioselective Mono and Multiple Alkylation of Diols and Polyols Catalyzed by Organotin and Its Applications on the Synthesis of Value‐Added Carbohydrate Intermediates.

AbstractA series of 3‐alkylated pyranosides, e.g. galactopyranosides (V), is prepared by a Bu2SnCl2‐catalyzed regioselective monoalkylation.

Super-heptazethrene.

The challenging synthesis of a laterally extended heptazethrene molecule, the super-heptazethrene derivative SHZ-CF3, is reported. This molecule was prepared using a strategy involving a multiple selective intramolecular Friedel-Crafts alkylation followed by oxidative dehydrogenation. Compound SHZ-CF3 exhibits an open-shell singlet diradical ground state with a much larger diradical character compared with the heptazethrene derivatives. An intermediate dibenzo-terrylene SHZ-2H was also obtained during the synthesis. This study provides a new synthetic method to access large-size quinoidal polycyclic hydrocarbons with unique physical properties.

Regioselective mono and multiple alkylation of diols and polyols catalyzed by organotin and its applications on the synthesis of value-added carbohydrate intermediates

A catalytic amount of dibutyltin dichloride was used to develop regioselective alkylation of diols and multiple alkylation of polyols. Alkyl groups, including allyl, alkynyl and long-chain alkyl groups, were successfully introduced to one or two hydroxyl groups of carbohydrate and nonsugar substrates. In most cases, excellent isolation yields were obtained. The alkynylated carbohydrates may be used to synthesize oligosaccharide mimics at a high efficiency via click reaction. The carbohydrates with long-chain alkyl groups may serve as surfactants, which were further demonstrated by experiments in this study.

ChemInform Abstract: Lewis Base Activation of Silyl Acetals: Iridium‐Catalyzed Reductive Horner—Wadsworth—Emmons Olefination.

AbstractA convenient scalable transformation of multiple challenging aryl, hetaryl, alkyl, and alkinyl esters as well as diesters into silyl acetals and the in‐situ transformation of the latter into enoates is elaborated.

Simple and Reproducible Sample Preparation for Single-Shot Phosphoproteomics with High Sensitivity.

The traditional sample preparation workflow for mass spectrometry (MS)-based phosphoproteomics is time consuming and usually requires multiple steps, e.g., lysis, protein precipitation, reduction, alkylation, digestion, fractionation, and phosphopeptide enrichment. Each step can introduce chemical artifacts, in vitro protein and peptide modifications, and contaminations. Those often result in sample loss and affect the sensitivity, dynamic range and accuracy of the mass spectrometric analysis. Here we describe a simple and reproducible phosphoproteomics protocol, where lysis, denaturation, reduction, and alkylation are performed in a single step, thus reducing sample loss and increasing reproducibility. Moreover, unlike standard cell lysis procedures the cell harvesting is performed at high temperatures (99 °C) and without detergents and subsequent need for protein precipitation. Phosphopeptides are enriched using TiO2 beads and the orbitrap mass spectrometer is operated in a sensitive mode with higher energy collisional dissociation (HCD).

ChemInform Abstract: Supramolecular Organogels Based on Dendrons and Dendrimers

AbstractReview: [93 refs.

Radical C-H alkylation of BODIPY dyes using potassium trifluoroborates or boronic acids.

A one-step synthetic procedure for the radical CH alkylation of BODIPY dyes has been developed. This new reaction generates alkyl radicals through the oxidation of boronic acids or potassium trifluoroborates and allows the synthesis of mono-, di-, tri-, and tetraalkylated fluorophores in a good to excellent yield for a broad range of organoboron compounds. Using this protocol, multiple bulky alkyl groups can be introduced onto the BODIPY core thus creating solid-state emissive BODIPY dyes.

Choline chloride based deep eutectic solvent as an efficient solvent for the benzylation of phenols

Deep eutectic solvents (such as the combination of urea and choline chloride) are found to be promising solvent and phase-transfer-media for benzylation of phenol. These methods avoided the complexity of multiple alkylations giving selectively O-alkylated aromatic products. Good to excellent yields of the corresponding benzyl phenyl ether were obtained. The non-toxic, biodegradable, inexpensive, and recyclable nature of DES make this protocol green and cost-effective.

Reaction pathways in the liquid phase alkylation of biomass‐derived phenolic compounds

Alkylation is a promising reaction for the upgrading of bio‐oil because it maximizes the retention of carbon in the liquid product. The alkylation of m‐cresol with isopropanol and HY zeolite was studied in a liquid phase system. The experimental results were fitted with two conventional surface kinetic models, Langmuir–Hinshelwood and Eley–Rideal, from which adsorption and rate constants were estimated. Two types of alkylation reactions were observed: C‐alkylation with formation of a CC bond with the ring and O‐alkylation with formation of an ether bond with the hydroxyl group. It was concluded that O‐alkylation products do not undergo intramolecular rearrangement but first decompose into the corresponding phenolic. Alkylation occurs from both isopropanol and propylene, both of them yielding O‐and C‐alkylation to different extents. Isopropanol favors O‐alkylation while propylene favors C‐alkylation. Rate constants for multiple alkylation steps were progressively lower, suggesting the presence of steric hindrance during incorporation of additional isopropyl groups. © 2014 American Institute of Chemical Engineers AIChE J, 61: 598–609, 2015

Supramolecular organogels based on perylenetetracarboxylic diimide trimers linked with benzenetricarboxylate

Two new perylenetetracarboxylic diimide (PDI) derivatives, namely, trimer 1 and trimer 2, composed of three PDI units with different tail groups, are prepared. Solubility of these two trimers is significantly different due to the different tail groups. The aggregation behavior of these two compounds in solution was investigated using absorption and fluorescence spectra. The results indicate that both trimers 1 and 2 can form large molecular aggregates via an intermolecular process in either good solvent or poor solvent. Trimer 1 can form gel in a mixed solvent of methanol and tetrahydrofuran (THF), while trimer 2 can only form gel in non-polar solvents, such as hexane and toluene. This can be ascribed to the multiple long alkyl chains in trimer 2, which have introduced extra hydrophobic interactions besides the π–π interactions between the molecules of trimer 2. The morphology examination of the dried gel of trimer 1 by atomic force microscopy (AFM) reveals simply long fibers. But, the dried gel of timer 2 shows network-like morphology, which can be ascribed to the hydrophobic interactions between the multiple alkyl chains.

Hierarchical self-assembly of a discrete hexagonal metallacycle into the ordered nanofibers and stimuli-responsive supramolecular gels

A discrete hexagonal metallacycle decorated with multiple amide groups and long hydrophobic alkyl chains was constructed via [3+3] coordination-driven self-assembly, from which the ordered nanofibers and stimuli-responsive supramolecular gels were successfully obtained via hierarchical self-assembly.

Rapid and serum-insensitive endocytotic delivery of proteins using biotinylated polymers attached via multivalent hydrophobic anchors

We have designed biotinylated polymers as synthetic receptors that have multiple alkyl groups for endocytotic delivery of target proteins. The polymers were stably attached to a cell surface via multivalent anchoring. The presented biotin was bound to streptavidin (SA) on the cell surface, and, via an endocytotic pathway, the cell rapidly internalized the biotinylated polymer/SA complex. The cell's uptake of the complex was not inhibited by the presence of 10% fetal bovine serum, and its efficacy for the uptake of SA was the highest when compared with commercial reagents and single-anchored-type synthetic receptors. The synthetic receptor-mediated endocytosis can be used generally for other kind of protein by using SA as an adaptor molecule between a target protein and the cell-surface presented biotin.

Solution Properties of Amphiphilic Telomers with Multiple Sugar Chains and Terminal Alkyl Chain

Amphiphilic telomers with multiple sugar chains and a terminal undecyl or heptadecyl chain (i.e., C(n)Am-mGEMA, where n and m represent alkyl chain lengths of 11 or 17 with a degree of polymerization of 2.0 or 3.0 for glucosyloxyethyl methacrylate (GEMA) units, respectively) were synthesized via monomeric radical telomerization in the presence of 2-aminoethanethiol hydrochloride. Surface tension, pyrene fluorescence, and dynamic light scattering were measured to characterize the solution properties of the synthesized telomers. In addition, the effects of alkyl chain length and degree of polymerization of hydrophilic GEMA units on the measured properties were evaluated by comparison with those of conventional polyoxyethylene dodecyl ether nonionic surfactants. C(n)Am-mGEMA telomers exhibited higher critical micelle concentration (CMC) values than polyoxyethylene dodecyl ether surfactants with similar number of hydrophilic groups did. The synthesized telomers are highly efficient in reducing the surface tension of water, despite the relatively large hydrophilic structures within the sugar units (GEMA). A unique behavior was observed in that adsorption at the air-water interface and solution aggregation occurred simultaneously at a concentration below CMC (as determined by the surface tension method). This suggests that aggregate formation occurs readily in solution along with the adsorption at the interface because of strong attractive interactions between multiple sugar GEMA chains. Further, aggregates formed by C(n)Am-mGEMA telomers differ depending on the number of sugar chains, i.e., an increase in the degree of polymerization of the telomers increases the size of the aggregates. This indicates that it is easier for telomers with more sugar GEMA chains to form large aggregates due to the interactions between their hydroxyl groups.