Amines 2a Research Articles

Fabrication of polyamide thin film composite membranes using aliphatic tetra-amines and terephthaloyl chloride crosslinker for organic solvent nanofiltration

Given the huge significance of organic solvents in several industrial processes, the use of membranes for recovering the solvents has evolved into an industrially viable process. The current work has been focused on studying the effect of minor changes in the chemistry of the reacting monomers on the organic solvent nanofiltration/solvent resistance nanofiltration (OSN/SRNF) performance of the membranes. The two aliphatic amines with varying aliphatic chain lengths between primary and secondary amines were selected for this purpose. Based on the structure of the resultant active layer, the Janus nanofiltration performance of the membrane was evaluated. The two membranes, 4A-TPC@crosslinked PAN and 4A-3P@crosslinked PAN were fabricated by using two different tetra-amines, 4A (N,N′-bis(3-aminopropyl)ethylenediamine) and 4A-3P (N,N′-Bis(2-aminoethyl)-1,3-propanediamine) crosslinked with terephthaloyl chloride (TPC) on a crosslinked polyacryonitrile (PAN) support through interfacial polymerization (IP). The presence of multiple hydrophobic –CH2– groups in the structures of the aliphatic amines 4A and 4A-3P develops hydrophobic sites in the hydrophilic polyamide active layers of the membranes. In addition, 4A has two secondary amino groups separated by ethylene (–CH2–CH2–) groups, whereas in 4A-3P, the two secondary amino groups are separated by propylene (–CH2–CH2–CH2–) leading to variation in the structural features and performance of the two membranes. Both membranes were fully characterized by several membrane characterization techniques and applied for OSN/SRNF using both polar (methanol, ethanol, and isopropanol) and non-polar (n-hexane and toluene) solvents. Different dyes (Congo red, Eriochrome black T, and Methylene blue) were used as model solutes during the filtration experiment. The 4A-3P-TPC@crosslinked PAN showed n-hexane and toluene flux of 109.9 LMH and 95.5 LMH, respectively. The Congo red (CR) showed the highest rejection, reaching 99.1% for the 4A-TPC@Crosslinked PAN membrane and 98.8% for the 4A-3P-TPC@Crosslinked PAN membrane.

Synthesis and Antibacterial Activity of Polyalthic Acid Analogs.

Polyalthic acid (PA) is a diterpene found in copaiba oil. As a continuation of our work with PA, we synthesized PA analogs and investigated their antibacterial effects on preformed biofilms of Staphylococcus epidermidis and determined the minimal inhibitory concentration (MIC) of the best analogs against planktonic bacterial cells. There was no difference in activity between the amides 2a and 2b and their corresponding amines 3a and 3b regarding their ability to eradicate biofilm. PA analogs 2a and 3a were able to significantly eradicate the preformed biofilm of S. epidermidis and were active against all the Gram-positive bacteria tested (Enterococcus faecalis, Enterococcus faecium, S. epidermidis, Staphylococcus aureus), with different MIC depending on the microorganism. Therefore, PA analogs 2a and 3a are of interest for further in vitro and in vivo testing to develop formulations for antibiotic drugs against Gram-positive bacteria.

The Synthesis and Absolute Configuration of Enantiomeric Pure (R)- and (S)-3-(piperidin-3-yl)-1H-Indole Derivatives

This article describes the synthesis of new chiral 3-(piperidin-3-yl)-1H-indole derivatives (R)-10a-c and (S)-11a-c from the corresponding diastereomers: (3R, 2R) and (3S, 2R)-2-[3-(1H-indol-3-yl)-1-piperidyl]-2-phenyl-acetamides (3R, 2R)-4a, (3R, 2R)-6b, (3R, 2R)-8c and (3S, 2R)-5a, (3S, 2R)-7b, (3S, 2R)-9c. Diastereomers were obtained by N-alkylation of derivatives of racemic 3-(piperidin-3-yl)-1H-indoles 1a-c using (S)-2-(4-toluenesulfonyloxy)-phenylacetic amide (S)-II. The same method was applied to obtain (3R, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3R, 2S)-2a and (3S, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3S, 2S)-3a diastereomers by treating amine 1a with (R)-2-(4-toluenesulfonyloxy)-phenylacetic acid methylester (R)-I. Systematic studies via single crystal X-ray crystallography were used to determine the molecular structure of the racemates 1a-c and the absolute configuration of the enantiomers. The solid racemates 1b and 1c were "true racemates" crystallizing in a centrosymmetric space group, while 1a formed a racemic conglomerate of homoenantiomeric crystals. The absolute configuration was determined for the enantiomeric pairs (R)-10a/(S)-11a, (R)-10b/(S)-11b, and (R)-12c/(S)-13c, as well as for (3S,2S)-3a. Spectra of 1H, 13CNMR, HPLC, and HRMS for diastereomers and enantiomers were consistent with the determined structures.

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

The Unexpected Selectivity Switching from Mitochondria to Lysosome in a D-π-A Cyanine Dye.

Two interesting benzothizolium-based D-π-A type hemicyanine dyes (3a–3b) with a diphenylamine (-NPh2) donor group were evaluated for fluorescence confocal microscopy imaging ability in live cells (MO3.13, NHLF). In sharp contrast to previously reported D-π-A dyes with alkyl amine donor (-NR2) groups (1), 3a and 3b exhibited significantly different photophysical properties and organelle selectivity. Probes 3a and 3b were nearly non-fluorescent in many polar and non-polar solvents but exhibited a bright red fluorescence (λem ≈ 630–640 nm) in stained MO3.13 and NHLF with very low probe concentrations (i.e., 200 nM). Fluorescence confocal microscopy-based co-localization studies revealed excellent lysosome selectivity from the probes 3a–3b, which is in sharp contrast to previously reported D-π-A type benzothiazolium dyes (1) with an alkyl amine donor group (-NR2) (exhibiting selectivity towards cellular mitochondria). The photostability of probe 3 was found to be dependent on the substituent (R’) attached to the quaternary nitrogen atom in the cyanine dye structure. The observed donor-dependent selectivity switching phenomenon can be highly useful in designing novel organelle-targeted fluorescent probes for live-cell imaging applications.

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

Zn(OTf)2-catalyzed hydroamination of ynamides with aromatic amines.

The Zn(OTf)2-catalyzed hydroamination of ynamides 2a-2l with aromatic amines 1a-1r was developed. This protocol features broad substrate scope of aromatic amines, good functional group tolerance for ynamides, and excellent regioselectivities. As a result, a variety of substituted amidine compounds 3aa-3oa, 3ab-3al and 3pa-3rk were prepared in moderate to excellent yields and with high regioselectivities.

Synthesis and Structure-Activity Relationship of 1-(2-Furoyl)Piperazine Bearing Benzamides as Butyrylcholinesterase Inhibitors

Four benzamide derivatives (5a, 5b, 8a, 8b) bearing heterocyclic furan and piperazine ring have been synthesized and evaluated for enzyme inhibition and hemolytic activity. Initial 4-(chloromethyl)benzoyl chloride (1) and 3-(chloromethyl)benzoyl chloride (6) were stirred with benzyl amine (2a) and cyclohexyl amine (2b), respectively, in aqueous medium at pH 9 – 10 maintained by aqueous sodium carbonate. The resulting benzamides (3a, 3b, 7a, 7b) were refluxed with 1-(2-furoyl)piperazine (4) in the presence of K2CO3 and CH3CN to acquire target compounds (5a, 5b, 8a, 8b). The spectroscopic techniques including 13C NMR, 1H NMR, IR and EI-MS corroborated the proposed molecular structures of final compounds. Among these, two compounds (5b, 8b) proved to be considerable inhibitors of butyrylcholinesterase enzyme. Study of the hemolytic activity potential revealed low toxicity level of compound 5b.

Small Chains of Main Group Elements by BH3 Adduct Formation of tBu2E‐N(H)‐EtBu2 (E = P, As)

Borane adducts of bis(di‐tert‐butylphosphanyl)amine (1a) and bis(di‐tert‐butylarsino)amine (1b) are reported. Based on quantum‐chemical investigations in combination with experimental results, it is demonstrated that the tautomerism known for tBu2P‐N(H)‐PtBu2 (1a), can be observed for the mono adduct tBu2P‐N(H)‐P(BH3)tBu2 (2a) as well, whereas for the corresponding arsenic compound 2b only one stable isomer is found. The bis‐borane adduct tBu2(BH3)As‐N(H)‐As(BH3)tBu2 (3b) is a rare example of a structurally characterized, tertiary arsine borane adduct, which can be directly compared with the corresponding phosphorus compound tBu2(BH3)P‐N(H)‐P(BH3)tBu2 (3a). Deprotonation of mixtures containing 2a by nBuLi leads to the lithium‐containing coordination polymer 4a, in which the actual chain consists only of non‐carbon atoms.

ZnO-nanorods Promoted Synthesis of α-amino Nitrile Benzofuran Derivatives using One-pot Multicomponent Reaction of Isocyanides

In this work ZnO-nanorod (ZnO-NR) as reusable catalyst promoted Strecker-type reaction of 2,4-dihydroxyacetophenone, isopropenylacetylene, trimethylsilyl cyanide (TMSCN), primary amines and isocyanides at ambient temperature under solvent-free conditions and produced α-amino nitriles benzofuran derivatives in high yields. These synthesized compounds may have antioxidant ability. ZnO-NRs in these reactions were prepared according to reported article. 2,4-dihydroxyacetophenone 1 (2 mmol) and isopropenylacetylene 2 (2 mmol) were mixed and stirred for 30 min in the presence of ZnO-NR (10 mol%) under solvent-free conditions at room temperature. After 30 min, primary amine 3 (2 mmol) was added to the mixture gently and the mixture was stirred for 15 min. After this time TMSCN 4 (2 mmol) was added to the mixture and stirred for 15 min. After completion of the reaction, as indicated by TLC, isocyanides 5 was added to mixture in the presence of catalyst. In the first step of this research, the reaction of 2,4-dihydroxyacetophenone 1, isopropenylacetylene 2, methyl amine 3a, trimethylsilyle cyanide 4 and tert-butyl isocyanides 5a was used as a sample reaction to attain the best reaction conditions. The results showed this reaction performed with catalyst and did not have any product without catalyst after 12 h. In conclusion, we investigate multicomponent reaction of 2,4-dihydroxyacetophenone 1, isopropenylacetylene 2, primary amines 3, trimethylsilyl cyanide 4 and isocyanides along with ZnO-NRs as reusable catalyst at room temperature under solvent-free conditions which generates α-amino nitrile benzofuran derivatives in high yields. The advantages of our method are high atom economy, green reaction conditions, higher yield, shorter reaction times, and easy work-up, which are in good agreement with some principles of green chemistry. The compounds 8c exhibit excellent DPPH radical scavenging activity and FRAP compared to synthetic antioxidants BHT and TBHQ.

Synthesis and characterization of amine-impregnated silica gel for potential carbon dioxide (CO2) absorption

The rising of CO2 concentration in atmosphere become global concern due to its effect to the global warming. One potentially economical for CO2 capture is through adsorption using solid sorbents. Silica gel has potential to adsorb carbon dioxide with modification of silica gel with amine groups which provide specific adsorption sides for carbon dioxide adsorption. Therefore, a study of impregnated silica gel with amine for carbon dioxide adsorption was done. A series of characterization was made between raw silica and impregnated silica with amine. Based on the results from Iodine Test Analysis and DSC characterization, it can be stated that the modification of Raw Desiccant Silica Gel (DSG) which had been modified with Aminopropyltrimethoxysilane (APMS), 95% had the highest possibilities of percentage to absorb CO2 from the environment with iodine value of 2736.85 mg/g that indicate the porosity and surface area of the adsorbent is higher. Amine 1A consist of 17.84 % of carbon, 5.41 % of hydrogen and 6.44 % of nitrogen. For FTIR result, Amine 1A has Si-O-Si stretching, C-C stretching, N-C stretching and C-N stretching due to the impregnation of amine to the raw silica gel. From DSC analysis, the higher the peak shows that water molecule bound to Amine 1A evaporated at a higher temperature of 92.4°C shows the highest porosity and have highest possibility as adsorbent for CO2 adsorption.

Copper-Catalyzed Asymmetric Formal Hydroaminomethylation of Alkenes with N,O-Acetals to Access Chiral β-Stereogenic Amines: Dual Functions of the Copper Catalyst

Chiral amines are synthetically versatile intermediates used for the preparation of a wide range of biologically active compounds and drugs. Compared with the well-developed synthesis of α-stereoge...

1,4-Dihydropyridine/BF3OEt2 for the reduction of imines: Influences of the amount of added BF3OEt2 and the substitution at N-1 and C-4 of the dihydropyridine ring

We have evaluated four 1,4-dihydropyridines (DHPs 1a, 1b, 1c and 1d) as reducing agents, which presented free (hydrogenated) or phenyl-substituted N-1 and C-4 positions of the DHP ring. Reactions combining each of the DHP and different amounts of BF3OEt2 were evaluated for the reduction of imine 2a (N-benzylideneaniline). DHP simultaneously substituted at N-1 and C-4 (1a), and DHP substituted at C-4 (1b) gave lower yields for reduction of 2a in comparison with DHPs 1c and 1d (both unsubstituted at the C-4 position). By evaluating the amount of added BF3OEt2 to the reaction mixture, we have found that DHP 1c (substituted at N-1) provided its best yield for amine 3a (82%) when associated with stoichiometric amounts BF3OEt2, while DHP 1d (N-1- and C-4-unsubstituted derivative) was more effective (90% yield) with catalytic quantities of the Lewis acid. The reaction system using DHP 1c under stoichiometric BF3OEt2 could also be successfully applied with additional imine examples and under reductive amination conditions.

Synthesis, Docking, and Pharmacological Evaluation of Derivatives of α‐Aminoketones Appended to Sydnones as Potent Antitubercular and Antifungal Scaffolds

3‐Arylsydnones are reported to possess striking pharmaceutical potency. α‐Aminoketone, a biologically active structural unit, is built at the fourth (electrophilic) position of sydnone and further derivatized with secondary amine and tetrazoles. The α‐aminoketone derivatives of sydnones coupled with secondary amines 4a–n were docked on enoyl acyl carrier protein (ACP) reductase from Mycobacterium tuberculosis, which revealed that compounds 4b, 4f, and 4i showed efficient C score values with different binding modes and hydrogen bonding. Further, these compounds were screened for antimycobacterial activity; among them, compound 4f displayed sensitivity at 6.25 μg/mL compared with the standard drug (Streptomycin) against M. tuberculosis (H37RV strain). In addition to this, α‐aminoketone derivatives of sydnones coupled with tetrazoles 8a–h were evaluated for antifungal activity. In the antifungal activity, compound 8b has exhibited potent activity at 6.25 μg/mL against Candida albicans and compound 8g at 0.4 μg/mL against Aspergillus fumigatus. The antifungal activities are comparatively better than standard antifungal agent Fluconazole at these drug concentrations. Alongside characterization of the final compounds by Fourier transform infrared, mass, 1H NMR, and 13C NMR spectral analyses, compounds 8b and 8g were confirmed by X‐ray crystallographic studies.

Immobilized Whole-Cell Transaminase Biocatalysts for Continuous-Flow Kinetic Resolution of Amines

Immobilization of transaminases creates promising biocatalysts for production of chiral amines in batch or continuous-flow mode reactions. E. coli cells containing overexpressed transaminases of various selectivities and hollow silica microspheres as supporting agent were immobilized by an improved sol-gel process to produce immobilized transaminase biocatalysts with suitable stability and mechanical properties for continuous-flow applications. The immobilized cell-based transaminase biocatalyst proved to be durable and easy-to-use in kinetic resolution of four racemic amines 1a–d. The batch and continuous-flow mode kinetic resolutions with transaminase biocatalyst of opposite stereopreference provided access to both enantiomers of the corresponding amines. By using the most suitable immobilized transaminase biocatalysts, this study describes the first transaminase-based approach for the production of both pure enantiomers of 1-(3,4-dimethoxyphenyl)ethan-1-amine 1d.

SNAr reactions of substituted pyridines with secondary amines in aqueous solution: Kinetic and reactivity indices in density functional theory

AbstractA kinetic study is reported for the reactions of 2‐methoxy‐3‐nitropyridine 1a and 2‐methoxy‐5‐nitropyridine 1b with three secondary amines 2a–c (morpholine, piperidine, and pyrrolidine) in aqueous solution at 20°C. The Brønsted‐type plots are linear with βnuc = 0.52 and 0.55 for pyridines 1a and 1b, respectively, indicating that the reaction proceeds through a SNAr mechanism in which the first step is the rate‐determining step. Additional theoretical calculations using the DFT/B3LYP method confirm that the C‐2 carbon being the most electrophilic center for the both pyridines 1a and 1b. The second‐order rate constants have been used to evaluate the electrophilicity parameters E of 1a and 1b according to the linear free energy relationship log k (20°C) = sN (N + E). The E parameters thus derived are compared with the electrophilic reactivities of a large variety of anisoles. The validity of these E values has been satisfactorily verified by comparison of calculated and experimental second‐order rate constants for the reactions of pyridines 1a and 1b with anion of ethyl benzylacetate.

Synthesis and Antimicrobial Activity of 4-Oxo-Thiazolidines and 5-Arylidene Derivatives of 2-Amino-5-Ethyl-1,3,4-Thiadiazole

A new series of 5-benzylidene-3-(5-ethyl-[1,3,4]thiadiazol-2-yl)-2-phenyl-thiazolidin-4-ones (3a-3m) were synthesized. The reaction of thioglycolic acid with benzylidene-(5-ethyl-[1,3,4] thiadiazol-2-yl)-amine 1a in the presence of anhydrous ZnCl2 afforded the new heterocyclic compounds 5-benzylidene-3-(5-ethyl-[1,3,4] thiadiazole-yl)-2-phenyl-thiazolidin-4-one, 2a. The latter product on treatment with several selected substituted aromatic aldehydes in the presence of sodium ethoxide underwent the Knoevenagel reaction to yield 5-benzylidene-3-(5-ethyl-[1,3,4] thiadiazol-2-yl)-2-phenyl-thiazolidin-4-ones, 3a-3m. The structures of the compounds were confirmed by IR, 1H-NMR, 13C-NMR and mass spectroscopy and by chemical analysis. All the above compounds were screened for their antimicrobial activity against some selected bacteria and fungi such as E. coli, B. Subtilis, and S. Typhi bacteria and A.niger, A. Flavus and F. oxisporium Fungi.
 Journal of Bangladesh Academy of Sciences, Vol. 42, No. 2, 155-170, 2018

Synthesis and antimicrobial activity of new 2-((1-furan-2-yl)ethylidene)hydrazono)-4-phenylthiazol-3(2H)-amine derivatives and their schiff bases with 4-nitrobenzaldehyde

A new series of 2-((1-furan-2-yl)ethylidene)hydrazono)-4-substitutedphenylthiazol-3(2H)-amines (2a–2o) and their Schiff bases (3a–3o) from 4-nitrobenzaldehyde were synthesized. The chemical structures of all the synthesized compounds were confirmed by their IR, 1H-NMR, 13C-NMR spectroscopy and mass spectrometry. They were screened for their antimicrobial and antifungal activities. Additionally, in vitro cytotoxic acivity of the most active antifungal compound (3o) and ketoconazole was determined in NIH/3T3 cells by MTT assay. Compound 2i (4-{3-Amino-2-[(1-(furan-2-yl)ethylidene)hydrazono]-2,3-dihydrothiazol-4-yl}phenol) showed the greatest antifungal activity among the newly synthesized derivatives. Schiff bases (3c-3n) displayed an undeniable fungicidal action against Candida parapsilosis ATCC 22019 as intense as the reference ketoconazole. In addition, the most active Schiff base 3o (2-[(1-(Furan-2-yl)ethylidene)hydrazono]-N-(4-nitrobenzylidene)-4-(2,3,4-trichloro phenyl)thiazol-3(2H)-amine) showed the highest antifungal activity against both Candida krusei ATCC 6258 and Candida parapsilosis ATCC 22019, and was as potent as ketoconazole. Moreover, compound 3o was found to be non-cytotoxic against NIH/3T3 cells.

Synthesis of Novel Thio-Substituted Aminonaphthoquinones

Novel thio-substituted aminonaphthoquinones were synthesized by the reactions of 2-(4-(trifluoromethyl)phenylamino)-3-chloronaphthalene-1,4-dione (3a) and 2-(3-(trifluoromethyl)phenylamino)-3-chloronaphthalene-1,4-dione (3b) with various thiol compounds such as ethanethiol (4a), methyl 2-mercaptoacetate (4b), ethyl 2-mercaptoacetate (4c). 2,3-dichloro-1,4-naphthoquinone (1) was reacted with aryl amines (2a, 2b) containing trifluoromethyl group to give compounds 3a and 3b by applying a method published in literature. Finally, obtained novel compounds (5a-5f) were characterized via IR, 1H NMR, 13C NMR, and MS techniques. Based on previous studies in the literature, it is expected that some potential biological activities of new compounds could find application in medicinal chemistry.

A rapid and green method for expedient multicomponent synthesis of N-substituted decahydroacridine-1,8-diones as potential antimicrobial agents

An efficient, green, high yielding, and quick method for the synthesis of N-substituted decahydroacridine-1,8-diones was achieved by multicomponent reaction between various aromatic aldehydes (1a–q), dimedone (2), and various aromatic amines (2a–d) using ChCl:Urea deep eutectic solvent as a recyclable organocatalyst and medium. The reaction conditions are relatively mild and do not require additional metals, acid catalysts, or organic solvents. The mild reaction conditions, experimental simplicity, straightforward purification procedures, excellent yields with short reaction times, as well as the application of green chemistry principles, are the advantages of this methodology. This simple ammonium deep eutectic solvent, easily synthesized from choline chloride and urea, is relatively inexpensive and biodegradable, making it applicable for industrial use. The deep eutectic solvent was easily separated and reused without loss of activity, and thus provides a good alternative. The synthesized 10-(substituted phenyl)-9-(substitutedphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8 (2H,5H)-diones (4a–l) were screened for their in vitro antimicrobial activity against four bacterial Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and three fungal strains (Candida albicans, Aspergillus niger and Aspergillus flavus). Among them, the 9-(N,N-Dimethylphenyl)-3,3,6,6-tetramethyl-10-(3-pyridyl)-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione (4f), 10-(4-Bromophenyl)-9-(3-hydroxy-4-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione (4i) and 9-(4-Nitrophenyl)-3,3,6,6-tetramethyl-10-phenyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione (4k) show good antimicrobial activity.