Condensation Step Research Articles

A dual optical probe with larger stokes shift for simultaneous detection of Cu2+ and Zn2+ ions and aggregation induced enhanced emission empowering selective detection of Cu2+ ions

A new aggregation induced enhanced emission (AIEE) active probe (1) has been synthesized via single step condensation reaction of 2-amino-3-benzyloxypyridine with 3-allylsalicylaldehyde in methanol. Probe 1 has been fully characterized by various spectroscopic techniques i.e. IR, NMR (1H and 13C), HRMS and X-ray crystallography. 1 displays a large stokes shift of 190 nm. It recognizes Cu2+ ions colorimetrically and fluorescence intensity enhances on the addition of Zn2+ ions. 1 form nanoaggregates in H2O:CH3OH (80:20, v/v) which detects Cu2+ ions selectively. 1 in the presence of Zn2+ ions and its nanoaggregates n1 show switch on behaviour of green fluorescence comparable to mitochondrial membrane potential indicator, Mitotracker-Red, in larval gut tissues of Drosophila melanogaster.

Route evaluation and development of a practical synthesis of methyl (S)-2-chloro-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-7-carboxylate

A rapid and reliable route to methyl ( S )-2-chloro-5,6,7,8-tetrahydropyrido[4,3- d ]pyrimidine-7-carboxylate moiety that is useful as a synthetic scaffold is described. Previously, this Boc-protected entity was prepared in 10 chemical steps starting with l -hydroxyproline with an overall yield of 0.67%. The newly developed synthetic route provided the desired target in seven chemical steps with an overall yield up to 38%. Three main issues that needed to be addressed with the previous route were; first, the ring expansion of the l -hydroxyproline that generated an inseparable regioisomeric mixture (1.5:1) by flash chromatography; secondly, the low yielding condensation step between the keto ester and urea; thirdly, the low yielding chlorination of the desired isomer. Starting with commercially available (2-chloropyrimidin-5-yl)methanol, the new route incorporates a Knochel iodination, a Negishi cross-coupling, and a ring closure as the key steps. This new route afforded us the opportunity to deliver enantiomerically pure intermediate in support of drug discovery efforts.

Glycerol Boosted Rh-Catalyzed Hydroaminomethylation Reaction: A Mechanistic Insight.

We report a Rh-catalyzed hydroaminomethylation reaction of terminal alkenes in glycerol that proceeds efficiently under mild conditions to produce the corresponding amines in relatively high selectivity towards linear amines, moderate to excellent yields by using a low catalyst loading (1 mol % [Rh], 2 mol % phosphine) and relative low pressure (H2 /CO, 1:1, total pressure 10 bar). This work sheds light on the importance of glycerol in enabling enamine reduction via hydrogen transfer. Moreover, evidence for the crucial role of Rh as chemoselective catalyst in the condensation step has been obtained for the first time in the frame of the hydroaminomethylation reaction by precluding deleterious aldol condensation reactions. The hydroaminomethylation proceeds under a molecular regime; the outcome of catalytically active species into metal-based nanoparticles renders the catalytic system inactive.

High-stakes testing policy and English language teaching: Voices of the leftovers

High-stakes testing has been controversial in many countries for several impacts and reasons surrounding its implementation. Teachers’ voices should be heard for well-rounded education policy. This study aims to investigate the voices of English teachers on the impacts of the national exam (NE) towards English language teaching at junior high schools (JHS) in Yogyakarta, Indonesia. It is a qualitative study involving three private JHSs and three state JHSs, chosen according to their NE-based ranks: low, mediocre, and high performing – for inclusive representation. The subjects are six English teachers from six JHSs. The data were collected through interviews and analyzed using the analysis model of Miles, Huberman, and Saldana, following the steps of data condensation, data categorization, data display, data interpretation, and conclusion drawing and verification. The findings show that NE leads to low order thinking skills, digresses from the goals of curriculum 2013, prioritizes only knowledge, focuses on English passive skills, induces favoritism between teachers, and disables teachers to vary their teaching strategies. Teachers’ involvement in education policy is necessary, and they are generally in favor of the NE abolishment plan. The implication of this study calls for implementing teachers' coping mechanism in transitioning from NE to the newly proposed assessment.

High-resolution infrared spectroscopy of naphthalene and acenaphthene dimers

Non-covalent interactions are rapidly gaining interest as they are often crucial in determining the properties of materials, and key to supramolecular chemistry and to biochemistry. Non-covalent Polycyclic Aromatic Hydrocarbon (PAH) complexes are in particular relevant to astrochemistry and combustion chemistry where they are involved in the initial steps of condensation and soot formation, respectively. Here, we investigated non-covalent π-π stacking and CH-π interactions in naphthalene and acenaphthene clusters using high-resolution IR-UV spectroscopy in combination with quantum chemical calculations. We identified spectral shifts that occur upon complexation and thereby evaluated predicted potential energy surfaces. Although theory predicts a blueshift, a redshift is observed for the aliphatic CH-π interactions in the experimental spectrum of acenaphthene upon dimerization, indicating that CH-π interaction indeed affects the aliphatic bonds, while a blueshift is predicted, consequently theory deserves attention here. The results provide strong indications for a prevalent parallel naphthalene dimer, showing that π-π stacking interactions become significant for bicyclic and larger PAHs.

Transition-Metal-Catalyzed Reductive Amination Employing Hydrogen.

The reductive amination, the reaction of an aldehyde or a ketone with ammonia or an amine in the presence of a reducing agent and often a catalyst, is an important amine synthesis and has been intensively investigated in academia and industry for a century. Besides aldehydes, ketones, or amines, starting materials have been used that can be converted into an aldehyde or ketone (for instance, carboxylic acids or organic carbonate or nitriles) or into an amine (for instance, a nitro compound) in the presence of the same reducing agent and catalyst. Mechanistically, the reaction starts with a condensation step during which the carbonyl compound reacts with ammonia or an amine, forming the corresponding imine followed by the reduction of the imine to the alkyl amine product. Many of these reduction steps require the presence of a catalyst to activate the reducing agent. The reductive amination is impressive with regard to the product scope since primary, secondary, and tertiary alkyl amines are accessible and hydrogen is the most attractive reducing agent, especially if large-scale product formation is an issue, since hydrogen is inexpensive and abundantly available. Alkyl amines are intensively produced and use fine and bulk chemicals. They are key functional groups in many pharmaceuticals, agro chemicals, or materials. In this review, we summarize the work published on reductive amination employing hydrogen as the reducing agent. No comprehensive review focusing on this subject has been published since 1948, albeit many interesting summaries dealing with one or the other aspect of reductive amination have appeared. Impressive progress in using catalysts based on earth-abundant metals, especially nanostructured heterogeneous catalysts, has been made during the early development of the field and in recent years.

One pot three component solvent free synthesis of N-substituted tetrazoles using RuO2 /MMT catalyst

A facile, one-pot three component catalytic method is developed for the synthesis of N-substituted tetrazole using RuO2/MMT nanocomposite. It is characterized with low and wide angle XRD which suggests that RuO2 nanoparticles are evenly dispersed on the surface of MMT while FESEM images indicate a spherical morphology having size in the range of 40-50 nm. The catalytic efficiency is evaluated for three component one-pot synthesis of the tetrazole using various amine, sodium azide and triethyl-ortho-formate under solvent free condition. This strategy has resulted in good to excellent yields (84 – 97%) of N-substituted tetrazoles within moderate reaction time. Moreover, the catalyst possesses excellent reusability up to five cycles with only 5% decrease in the yield of tetrazole after 5th cycle. The beneficial catalytic activity of the bifunctional nanocomposite is attributed to the uniformly dispersed RuO2 nanoparticles on the surface of MMT where RuO2 site is responsible for coordination of isocyanide intermediate while strong acidic character of MMT induces condensation and cyclization steps in a synergic manner. Thus, it can be argued that RuO2/MMT nanocomposite possesses potential applications for Multi Component Reactions (MCR) in terms of efficient and sustainable manner.

Nanomaterial assisted bulk scale synthesis of 2-methyl-6-nitroquinoline

Quinolines are an interesting class of moieties with various medicinal chemistry uses. The most prominent is their ability to be used as the last line of therapy for bacterial and viral infections including recent COVID-19. The synthesis of quinoline is through a cyclization reaction and overall reaction yields are about 20%. The bulky ring and the associated crowding of functional groups limit the catalyst options. In this publication, the use of Fe3O4@SiO2for enhancing yield improvements, especially for heterocyclics is reported. The use of the 40 nm sized silica functionalized magnetite nanoparticles seems to help in both condensation and cyclization steps of representative 2-methyl-6-nitroquinoline. Reaction time reduction due to surface enabled catalysis of nanoparticles is 110 min to 80 min. The reaction yield has doubled due to the presence of catalyst and the mechanism suggests this drastic result is due to stabilization of unstable intermediate on the acidic surface of the silica coating. This near homogeneous catalysis of 40 nm sized, silica functionalized, magnetite nanoparticles have far reaching applications in bulk drug industry for drugs like chloroquine & hydroxychloroquine, the two essential drugs for prophylactic use for COVID-1.

Selective hydrogenolysis of biomass-derived sorbitol to propylene glycol and ethylene glycol on in-situ formed PdZn alloy catalysts

Sorbitol hydrogenolysis to industrially important propylene glycol and ethylene glycol receives increasing attention, recently. Here, we developed an efficient and stable PdZn alloy catalyst, in-situ formed from a physical mixture of Pd/ZrO2 and ZnO, for the sorbitol hydrogenolysis with Mg3AlOx as a solid base, and obtained a 54.6% yield of the two target glycols (493 K and 5.0 MPa H2). The amounts of ZnO and Mg3AlOx strongly influenced the activity and selectivity, due to their effects on the formation of the PdZn alloys and the competitive metal-catalyzed dehydrogenation/hydrogenation and base-catalyzed retro-aldol condensation steps. The kinetic isotope effects, combined with the inhibiting effects of H2 pressure on the activity in a broad range (3.0–8.0 MPa), confirm that the sorbitol dehydrogenation to hexose intermediates is the kinetically-relevant step in the sorbitol hydrogenolysis. This study provides insights into the catalytic functions and reaction parameters for the hydrogenolysis of polyols to the target glycols.

Multistage Self-Assembly Strategy: Designed Synthesis of N-doped Mesoporous Carbon with High and Controllable Pyridine N Content for Ultrahigh Surface-Area-Normalized Capacitance

Nitrogen doping could improve the performance of carbon materials in electrocatalysis, CO2 adsorption, and energy storage. [1]However, the control of the doping type and the amount of nitrogen (N)-...

One-Pot Synthesis of α,β-Unsaturated γ-Lactones and Lactams via a Sequential trans-Hydroalumination and Catalytic Carboxylation of Propargyl Alcohols and Amines with Carbon Dioxide.

A one-pot, sequential process that combines a trans-selective hydroalumination of propargyl alcohols and amines with a copper- or silver-catalyzed carboxylation reaction using carbon dioxide, followed by an acid-mediated intramolecular condensation step, led to the formation of a wide range of α,β-unsaturated γ-butyrolactones and lactams.

Synthesis, Characterization and In Vitro Antibacterial Derivatives of Doxycycline

Objective: Nowadays antibacterial drugs resistance is major problem in the world. To overcome this problem, some novel derivates of doxycycline were synthesized by single step condensation reaction with ten different types of aromatic and aliphatic aldehydes and ketones in ethanol as solvent and acetic acid as catalyst. In these reactions, deprotonation of primary amine occurs that results in formation of imine. 
 Methods: All the derivatives physically characterized and confirmed by analytical techniques i.e. FTIR and 1H NMR and 13C NMR. The derived compounds have exhibited significantly more active against both gram positive as well as gram negative bacterial strains as compared to parent drug.
 Results: Derived Schiff bases RDC2, RDC4 and RDC10 showed zone of inhibition against Bacillus subtilis as compared to doxycycline and derived Schiff bases RDC1, RDC2, RDC5, RDC6, RDC7 and RDC8 showed more zone of inhibition against Micrococcus luteus as compared to doxycycline. Yield (75%), m.p. 180-185°C, Mol. Wt. 1063, Elemental Analysis: (Calculated) for C58H54N4O16: iC, 65.53; H, 5.12; N, 5.27; (Found): C, 65.49; H, 5.18; N, 5.37; FTIR (ν, cm‐1): 3066 (=C-H), 1665(C=N), 1585, 1490(C=C, phenyl), 3650(OH), 1692 (C=O); 1H NMR (DMSO−d6, δ, ppm), 6.02-6.03 d, 6.91-6.92 d, (=CH-); 6.88-6.89 t (=CH), 2.89-2.90 d, (-CH); 1.07-1.08 q, (-CH3), 3.38-3.39 d; 3.17-3.18 d, (CH), 1.47-1.48 t (CH), 1.48 s, (CH3), 6.96-6.97d, 7.577-7.588 d, (-CH=) 15.21 s (OH); 4.62 s (OH); 1.46-1.47 s (OH); 13C NMR (DMSO−d6, δ, ppm).
 Conclusion: Doxycycline is among broad-spectrum tetracycline. The Schiff bases derived from doxycycline show significantly highly active against gram negative bacteria as compared to doxycycline. In future further study on these derived compounds will help in market new derivative of doxycycline, which will have more broad-spectrum activity than doxycycline.

Energy efficiency of membrane vs hybrid membrane/cryogenic processes for propane recovery from nitrogen purging vents: A simulation study

When pure propane contained in pipelines or storage tankers has to be flushed out by nitrogen fluxes for maintenance purpose, propane recovery is obviously of interest both for environmental issue and for propane valorization. A low temperature condensation is generally used for that purpose and is attractive because it allows to recover propane under liquid state. However, the energy required is very important to reach a high recovery separation target. An alternate approach can be the combination of a nitrogen or propane permselective membrane with a conventional condensation step to improve the global efficiency of the separation process. The present work has been intended to investigate this approach and evaluate to which extent a hybrid process can bring an added value. This study shows first a map of membrane separation performance of propane over nitrogen from data of the open literature. Interestingly it shows that either N2-selective or conversely, propane-selective membranes can be used and also that propane–selective membrane will require higher area for atmospheric down-stream pressures (1 bar) compared to down-streams kept at lower pressures (0.1 bar). The selection of the most nitrogen and propane selective membrane is used in order to simulate hybrid processes where separations performances (purity of the propane condensed versus energy required) are compared to the baseline cryogenic standalone process. For low propane contents in the feed mixture (xin,C3H8 = 0.5 and 5% mol/mol), it is shown that the use of a propane selective membrane module with a vacuum system seems to be the most energy efficient process while reaching a high purity (>98%). Based on rigorous process simulations, other hybrid processes cases were performed considering SSZ-13 zeolite membranes and the different separation performances are discussed. It is shown that a membrane/cryogenic process can indeed be less energy demanding to recover propane from N2-vents. However, according to the recovery target the choice of the membrane type can vary from an organic to a zeolite membrane.

Preparation and uranium (VI) biosorption for tri-amidoxime modified marine fungus material.

The preparation, characterization, and uranium (VI) adsorption properties of tri-amidoxime modified marine fungus material (ZZF51-GPTS-EDA-AM/ZGEA) were investigated in this study. ZGEA was synthesized by four steps of condensation, nucleophilic substitution, electrophilic addition, and nitrile amidoxime and characterized by a series of methods containing FT-IR, TGA, SEM, and BET. Contrasted with uranium (VI) adsorption capacity of original fungus mycelium (15.46mgg-1) that of the functional material (584.60mgg-1) was great under the optimal factors such as uranium (VI) ion concentration 40mgL-1, solid-liquid ratio 50mgL-1, pH of solution 5.5, and reaction time 120min. The above data were obtained by the orthogonal method. The cyclic tests showed that ZGEA had good regeneration performance, and it could be recycled at least five adsorption-desorption processes. The thermodynamic experimental adsorption result fitted Langmuir and Freundlich models, which explored monolayer and double layers of uranium (VI) adsorption mechanism, and the kinetic adsorption results were in better consistent with the pseudo-second-order and pseudo-first-order dynamic models (R2> 0.999).

Aqueous Phase Aldol Condensation of Formaldehyde and Acetone on Anatase TiO2(101) Surface: A Theoretical Investigation

AbstractA mechanistic understanding of catalytic reactions at solid‐liquid interface is limited both experimentally and theoretically but attracts much interest. Using density functional theory calculations (DFT) and ab initio molecular dynamics (AIMD) simulations, we investigated the effect of liquid water on α‐H abstraction, C−C coupling, and dehydration steps of aldol condensation of formaldehyde and acetone on an anatase TiO2(101) surface. The existence of the aqueous phase lowered the Gibbs energy of activation of dehydration step pronouncedly from 187 to 74 kJ/mol through proton transfer mechanism, making the hydrogenation pathway more favorable in the aqueous phase. In contrast, a mixed route prevails in the vapor phase. This work provides insights into the effect of the bulk water through a proton transfer mechanism on the dehydrogenation, C−C coupling, and dehydration steps.

A modular approach to the bisbenzylisoquinoline alkaloids tetrandrine and isotetrandrine.

An efficient racemic total synthesis of the bisbenzylisoquinoline alkaloids tetrandrine and isotetrandrine in four different routes is reported herein. Key steps of the synthesis include N-acyl Pictet-Spengler condensations to access the tetrahydroisoquinoline moieties, as well as copper-catalyzed Ullmann couplings for diaryl ether formation. Starting from commercially available building blocks tetrandrine and isotetrandrine are accessed in 12 steps. Depending on the sequence of the four central condensation steps, equimolar mixtures of both diastereomers or predominantly tetrandrine or its diastereomer isotetrandrine are obtained. Through computational analysis we were able to rationalize the differences in the observed diastereomeric specificities.

Yttria-Stabilized Zirconia as a High-Performance Catalyst for Ethanol to n-Butanol Guerbet Coupling.

It has been shown that yttria-stabilized zirconia is an effective catalyst for ethanol to n-butanol Guerbet coupling. The variation of the calcination temperature allows an improvement in the catalytic characteristics of this material via stabilization of the tetragonal phase of zirconia, having higher basicity than the monoclinic one. The treatment of yttria-stabilized zirconia at an optimal calcination temperature of 500 °C induces the increase in surface basicity required for the aldol condensation step, along with a decrease in surface acidity, which is responsible for the side reaction such as ethylene formation. The catalyst obtained significantly exceeds in selectivity and n-butanol yield than individual zirconia and other oxide systems which have been studied in this reaction.

Microscopic visualization of heterogeneous nucleation process on smooth spherical particle: Method and results

Heterogeneous nucleation is a very fundamental step in vapor condensation. However, it is scarcely possible to directly visualize the nucleation process because it is very quick and complicated. In present work, a method is proposed to create a mixed surface, where the hydrophilic SiO2 particle is dispersed on the super-hydrophobic substrate for a direct visualization of the nucleation process. The time-resolved images are recorded by Environmental Scanning Electron Microscopy (ESEM) system. The results indicate that only one embryo drop forms at a random point of a single particle surface and subsequently grows up and finally wraps the single particle. For multiple particles, the embryo drop occurs on the junction of particles and continues to enlarge to finally wrap all the particles. The numerical analysis shows that the nucleation ability of SiO2 is qualitatively consistent with the theoretical prediction, and quantitatively, the experimental Scr is much smaller than the predicted results.

AIE-Active and Thermoresponsive Alternating Polyurethanes of Bile Acid and PEG for Cell Imaging

Alternating polyurethanes (PUs) of poly(ethylene glycol) (PEG) and bile acids were synthesized through a single step condensation and then conjugated with a tetraphenylethene (TPE) derivative, a ty...

A simple schiff base as a multi responsive and sequential sensor towards Al3+, F− and Cu2+ ions

A novel and simple Schiff base receptor (AHN) synthesized via single step condensation of 1-Aminoanthracene and 2-hydroxynaphthaldehyde has been reported. This receptor provides dual mode selective detection of Al3+ and F− ions through UV–vis., (naked-eye) and ‘off-on’ fluorescence spectral changes, causing 640-folds enhancement in fluorescence in presence of F- ions in CH3CN. The “in-situ” generated AHN:F− complex has been exploited to act as a sequential chemosensor for Cu2+ ions with on-off fluorescence response. The values for limit of detection were found to be 1.48, 1.44 and 2.05 μM for Al3+ F− and Cu2+ ions, respectively.