Stepwise Nucleophilic Substitution Research Articles

2-(Butylamino)-6-chloro-4-[3-(7-chloro-4-quinolylamino)propylamino]-1,3,5-triazine

We herein report the synthesis of a 7-chloro-aminoquinoline triazine conjugate. The s-triazine library was generated by stepwise nucleophilic substitution of cyanuric chloride with butylamine. The structure of the compound was comprehensively determined using various analytical techniques, including proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), heteronuclear single quantum coherence (HSQC), and Distortionless Enhancement by Polarization Transfer (DEPT-135) experiments. Additionally, ultraviolet (UV) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and high-resolution mass spectrometry (HRMS) were employed for full characterization. Preliminary studies explored the potential interaction of the molecule with dihydrofolate reductase (DHFR) using molecular modeling. Furthermore, its drug-likeness was assessed by predicting relevant pharmacokinetic properties.

Advancing energy safety via stepwise nucleophilic substitution on tetrazine

This study presents a feasible approach to synthesizing hydrazine/nitroamine and amino/nitroamine substituted tetrazine derivatives.

Multistep synthesis, reactivity and X-ray structure of the anisole-terminated iron(II) polyhalogenoclathrochelates and their monoribbed-functionalized macrobicyclic derivatives

Multistep synthetic pathway towards a series of the anisoleboron-capped ribbed-functionalized iron(II) cage complexes was developed. Their hexachloroclathrochelate precursor was obtained by the template condensation of three dichloroglyoximate chelating ligand synthons with two molecules of 4-methoxyphenylboronic acid as a Lewis-acidic cross-linking agent on the iron(II) ion as a matrix. It easily underwent a stepwise nucleophilic substitution with S2- and O2-dinucleophilic aliphatic (ethanedithiolate) or aromatic (pyrocatecholate) agents, forming the stable X2 (X = S or O)-six-membered ribbed substituent(s) at a quasiaromatic cage framework. Performing these reactions under the different reaction conditions (i.e., at various hexachloroclathrochelate-to-nucleophile molar ratios, a wide range of temperatures and a series of the solvents) allowed to control a predominant formation of its mono-, di- or triribbed-substituted macrobicyclic derivatives. Thus obtained iron(II) di- and tetrachloroclathrochelates can undergo their post-synthetic transformations with active nucleophilic agents. The latter complexes underwent a further nucleophilic substitution with the anionic derivative of n-butanthiol, thus giving the hexasulfide macrobicyclic compound with two functionalizing n-alkyl substituents in one of its three chelate α-dioximate fragments and two apical biorelevant anisole substituents. The obtained iron(II) clathrochelates, possessing a low-spin electronic d6 configuration, were characterized using elemental analysis, MALDI-TOF mass spectrometry, UV–Vis, 1H and 13C{1H} NMR spectroscopies, and by the single-crystal X-ray diffraction experiments for the hexachloroclathrochelate precursor, its dichlorotetrasulfide macrobicyclic derivative and the monoribbed-functionalized hexasulfide cage complex. In all their molecules, the encapsulated iron(II) ion is situated in the centre of its FeN6-coordination polyhedron, the geometry of which is intermediate between a trigonal prism and a trigonal antiprism with the distortion angles φ from 21.4 to 23.4°. Halogen bonding between the polyhalogenoclathrochelate molecules in their crystals is observed.Graphical abstract

Monoribbed‐Functionalized Macrobicyclic Iron(II) Complexes Decorated with Terminal Reactive and Vector Groups: Synthetic Strategy, Chemical Transformations and Structural Characterization

Comprehensive SummaryGeneral and straightforward synthetic strategy towards the iron(II) clathrochelates with functionalizing substituents in their apical capping and one of the three chelate ribbed fragments was developed. Their hexachloroclathrochelate precursors were prepared by the direct template condensation of dichloroglyoxime with a suitable boronic acid on the Fe2+ ion as a matrix and underwent a stepwise nucleophilic substitution with S2‐, N2‐ or O2‐bis‐nucleophiles, forming the alicyclic or aromatic N2‐, S2‐ or O2‐six‐membered fragments. Depending on the reaction conditions and precursor‐to‐dinucleophile molar ratios, iron(II) clathrochelates with one (S, O and N), two (S, O and N) or three (S and O) X2‐six‐membered ribbed substituent(s) were obtained. Their reactivity substantially decreases in a row: Cl6‐Cage > Cl4X2‐Cage (where X = S, O or, especially, N) > Cl2X4‐Cage (where X = S or O). The reactive monoribbed‐functionalized clathrochelates underwent further chemical transformations giving the target macrobicyclic complexes with terminal vector groups. As follows from the single crystal XRD data, their FeN6‐coordination polyhedra possess the geometry intermediate between a trigonal prism and a trigonal antiprism (φ = 21.3°—25.20°). Fe—N distances vary from 1.887(6) to 1.933(8) Å. Their 3D‐molecules, the hydrophobic–hydrophilic balance in which can be tuned using a ribbed functionalization, form in the crystals the intermolecular specific halogen bonds and/or hydrophobic interactions.

Synthesis of Multifunctional Charge-Transfer Agents: Toward Single-Walled Carbon Nanotubes with Defined Covalent Functionality and Preserved π System

The attachment of well-defined charge transfer agents to the surface of nanomaterials is an efficient strategy to control their charge density and also to tune their optical, electrical, and physicochemical properties. Particularly interesting are charge transfer agents that either donate or withdraw electrons depending on the arrangements of their building units and that promise a non-destructive attachment to delicate nanomaterials like sp$^2$ compounds. In this work, we rationally synthesize molecular moieties with versatile functionalities. A reactive anchor group allows to attach them to carbon nanotubes as defined charge transfer agents while preserving the tube $\pi$-conjugation. The charge transfer agents were synthesized through the stepwise nucleophilic substitution of either one (monosubstituted series) or two chlorine (disubstituted series) atoms of cyanuric chloride by aniline derivatives containing one, two or three methoxy groups in the para and meta positions. Variation in the number and position of methoxy as an electron transferring group help us to manipulate the electronic and optical properties of the molecular probes and their charge transfer to the SWNTs systematically. The correlation between the optical properties of these molecular probes and their functionality was investigated by experiments and quantum chemical calculations. While the optoelectronic properties of the conjugated charge transfer agents were dominated by the aniline segments, the triazine warrants the ability to nondestructively attach to the surface of SWNTs. This study is one step ahead towards the production of SWNTs with desired optical and electrical properties by covalent $\pi$-preserving functionalization.

Transition-Metal-Free Coupling of Polyfluorinated Arenes and Functionalized, Masked Aryl Nucleophiles.

A chemoselective C(sp2)−C(sp2) coupling of sufficiently electron‐deficient fluorinated arenes and functionalized N‐aryl‐N’‐silyldiazenes as masked aryl nucleophiles is reported. The fluoride‐promoted transformation involves the in situ generation of the aryl nucleophile decorated with various sensitive functional groups followed by a stepwise nucleophilic aromatic substitution (SNAr). These reactions typically proceed at room temperature within minutes. This catalytic process allows for the functionalization of both coupling partners, furnishing highly fluorinated biaryls in good yields.

Stepwise Nucleophilic Substitution to Access Saturated N-heterocyclic Carbene Haloboranes with Boron–Methyl Bonds

Compounds of boranes with N-heterocyclic carbenes are known, yet little attention has been paid to NHC compounds of boron bearing methyl and halogen moieties together. The reason can be attributed ...

Donor-Pi-Acceptor Fluorene Conjugates, Based on Chalcone and Pyrimidine Derivatives: an Insight into Structure-Property Relationship, Photophysical and Electrochemical Properties.

A small set of four new fluorenyl chromophores (5-5a-c) was accomplished by stepwise nucleophilic substitution, Friedel-Crafts acylation, Ullman coupling, aldol condensation and cyclization reactions. The fluorene moiety was substituted at 2,7,9 and 9' positions with diverse groups. The synthesized derivatives were characterized by FTIR, 1H-NMR and 13C-NMR spectroscopic techniques. The optical properties were evaluated by by UV-VIS absorption and Fluorescence studies. HOMO and LUMO energy levels were evaluated by electrochemical studies and were found at -5.37-5.83eV and - 2.47-2.94eV respectively with band gap energy values 2.88 to 2.91eV. The band gap energy values suggested that these synthesized molecules can be manipulated in the designing of blue and green OLEDS. Graphical Abstract.

Synthesis, biological evaluation, and in silico studies of novel chalcone- and pyrazoline-based 1,3,5-triazines as potential anticancer agents.

A novel series of triazin-chalcones (7,8)a–g and triazin-N-(3,5-dichlorophenyl)pyrazolines (9,10)a–g were synthesized and evaluated for their anticancer activity against nine different cancer strains. Triazine ketones 5 and 6 were synthesized from the cyanuric chloride 1 by using stepwise nucleophilic substitution of the chlorine atom. These ketones were subsequently subjected to a Claisen–Schmidt condensation reaction with aromatic aldehydes affording chalcones (7,8)a–g. Then, N-(3,5-dichlorophenyl)pyrazolines (9,10)a–g were obtained by cyclocondensation reactions of the respective chalcones (7,8)a–g with 3,5-dichlorophenylhydrazine. Among all the evaluated compounds, chalcones 7d,g and 8g exhibited more potent in vitro anticancer activity, with outstanding GI50 values ranging from 0.422 to 14.9 μM and LC50 values ranging from 5.08 μM to >100 μM. In silico studies, for both ligand- and structure-based, were executed to explore the inhibitory nature of chalcones and triazine derivatives. The results suggested that the evaluated compounds could act as modulators of the human thymidylate synthase enzyme.

Discovery of new ureido benzenesulfonamides incorporating 1,3,5-triazine moieties as carbonic anhydrase I, II, IX and XII inhibitors.

A series of twenty novel ureido benzenesulfonamides incorporating 1,3,5-triazine moieties substituted on one side with aromatic amines and on the other side with dimethylamine, morpholine and piperidine is reported. The compounds were synthesized from the 4-(3-(4,6-dichloro-1,3,5-triazin-2-yl)ureido)benzensulfonamide (1) by using stepwise nucleophilic substitution of the chlorine atoms of cyanuric chloride. The intermediates 2(a-e) and final compounds 3(a-o) were tested for their efficiency as carbonic anhydrase (CA) inhibitors against four selected physiologically relevant human carbonic anhydrase (CA, EC 4.2.1.1) isoforms, namely, the cytosolic ones hCA I and II, and the transmembrane, tumor associated ones hCA IX, and XII. The compounds 2a, 2e and 3m showed the highest activity for hCA IX with Kis in the range of 11.8-14.6 nM. Most of the compounds showed high hCA IX selectivity over the abundant off-target isoforms hCA I and II. Since hCA IX is a validated drug target for anticancer/antimetastatic agents, these isoform-selective and potent inhibitors may be considered of interest for further medicinal/pharmacologic studies.

Microwave Irradiation Assists the Synthesis of a Novel Series of bis-Arm s-Triazine Oxy-Schiff Base and Oxybenzylidene Barbiturate Derivatives.

A novel series of s-triazines incorporating 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde was prepared and fully characterized. The reaction was carried out via stepwise nucleophilic aromatic substitution of chlorine atoms in cyanuric chloride. The first chlorine was substituted by different amines (morpholine, piperidine, or diethylamine) to afford 2,4-dichloro-6-substituted-1,3,5-triazine. The second and third chlorines were substituted by benzaldehyde derivatives in the presence of Na2CO3 as a HCl scavenger to afford the target products: s-triazine oxyaldehyde derivatives (dipodal). The dipodal derivatives were reacted with acid hydrazide, hydralazine, barbituric, or thiobarbituric acid derivatives using conventional heating or microwave irradiation to afford the di-arm s-triazine oxy-Schiff base and oxybenzylidene barbiturate derivatives in good yields. Microwave irradiation done in less solvent afforded the target product in less reaction time with good yield and purity. These types of derivatives might have special interest in coordination and medicinal chemistry.

A computational study on the mechanism of ynamide-mediated amide bond formation from carboxylic acids and amines.

This paper reports a computational study elucidating the reaction mechanism for ynamide-mediated amide bond formation from carboxylic acids and amines. The mechanisms have been studied in detail for ynamide hydrocarboxylation and the subsequent aminolysis of the resulting adduct by an amine. Ynamide hydrocarboxylation is kinetically favorable and thermodynamically irreversible, resulting in the formation of a key low-lying intermediate CP1 featuring geminal vinylic acyloxy and sulfonamide groups. The aminolysis of CP1 by the amine is proposed to be catalyzed by the carboxylic acid itself that imparts favourable bifunctional effects. In the proposed key transition state TSaminolysis-acid-iso2, the amine undergoes direct nucleophilic substitution at the acyl of CP1 to replace the enolate group in a concerted way, which is promoted by secondary hydrogen bonding of carboxylic acid with both the amine and CP1. These secondary interactions are suggested to increase the nucleophilicity of the amine and to activate the Cacyl-O bond to be cleaved, thereby stabilizing the aminolysis transition state. The concerted aminolysis mechanism is competitive with the classic stepwise nucleophilic acyl substitution mechanism that features sequential amine addition to acyl/intramolecular proton transfer/C-O bond cleavage and a key tetrahedral intermediate. Based on the mechanistic model, the carboxylic acid substrate effect and studies of more acidic CF3SO3H as the catalyst are in good agreement with the experimental observations, lending further support for the mechanistic model. The bifunctional catalytic effect of the carboxylic acid substrate may widely play a role in related amide bond-forming reactions and peptide formation chemistry.

Soluble, microporous ladder polymers formed by stepwise nucleophilic substitution of octafluorocyclopentene

A series of ladder polymers were prepared by reacting octafluorocyclopentene (OFCP) with various bisphenols at or above room temperature. The ladder polymers were synthesized in one or two steps with similar or different bisphenols due to different reactivities of fluorine atoms at vinylic (1,5) and (2,4) allylic positions of OFCP.

Erratum to: “Nucleophilic Substitution in 4-Bromo-5-nitrophthalodinitrile: XI. Preparation, Properties, and Prediction of Mesomorphism in Mixed-Substituted Phthalocyanines Containing Aryloxy and Benzotriazole Fragments”

Stepwise nucleophilic substitution of bromine and nitro group in 4-bromo-5-nitrophthalodinitrile has led to a series of phthalonitriles containing benzotriazole and aryloxy fragments; basing on them, the mixed-substituted phthalocyanines have been prepared. The spectral properties of products have been studied. According to simulation of columnar mesomorphism only one of the products is not capable of mesomorphism characteristic of discotic mesogens; the result has been confirmed with the experiment.

ChemInform Abstract: Regioselective Preparation of Functional Aryl Ethers and Esters by Stepwise Nucleophilic Aromatic Substitution Reaction.

AbstractA wide variety of fluorinated aryl ethers and esters is prepared by nucleophilic aromatic substitution reaction of fluorinated benzonitriles with phenols or benzoic acid whereas, etherification can be performed stepwise or in an one‐step procedure.

Regioselective preparation of functional aryl ethers and esters by stepwise nucleophilic aromatic substitution reaction

Functional aryl ethers bearing mono- and di-substituted azo compounds, allyl functionalities, vinyl phenyl moieties, trifluoromethyl (CF3) groups, etc. were prepared by nucleophilic substitution reaction of 2,3,4,5,6-pentafluorobenzonitrile (PFBN) in a stepwise manner at room temperature in dipolar aprotic solvents in a regioselective manner. Mono substituted aryl ether further underwent two more substitutions at ortho and ortho′ positions either with the same or different phenoxides. However, para substituted monoesters as well as para-ether-ortho-ester obtained by using carboxylates as (one of the) nucleophiles did not undergo any further displacement. The synthetic strategy described here is useful for making various functional materials such as lubricants, liquid crystals, curing agents, pigments and superhydrophobic materials.

Ferrous-activated persulfate oxidation of arsenic(III) and diuron in aquatic system

In situ chemical oxidation (ISCO) can be an effective technology for the remediation of soil and groundwater polluted by organic and inorganic contaminants. This study investigated the oxidation of arsenic(III) (As(III)) and diuron using ferrous activated persulfate-based ISCO. The results indicated that Fe(II)/persulfate oxidation could be an effective method to oxidize As(III) and diuron. Effects of pH, S2O82− and Fe(II) amounts on the destruction of As(III) and diuron were examined in batch experiments. Acidic conditions favored the removal of As(III) and diuron. Four chelating agents, citric acid (CA), Na2S2O3, diethylene triamine pentaacetic acid (DTPA) and ethylene diamine tetraacetic acid disodium (EDTA-Na2) were used in attempt to maintain the quantity of ferrous ion in solution. In our experiments, CA and Na2S2O3 were found to be more effective than DTPA and EDTA-Na2. Our results also revealed a widely practical prospect of inorganic chelating agent Na2S2O3. Hydroxyl and sulfate radical were determined to play key roles in the oxidation process by using ethanol and tertiary butanol as molecular probes. Oxidation of As(III) yielded As(V) via the electron-transfer reaction. In the oxidation process of diuron, a stepwise nucleophilic substitution of chlorine by hydroxyl and a stepwise oxidation process of the methyl on the dimethylurea group by hydroxyl and sulfate radical were proposed.

Position-specific isotope analysis of the methyl group carbon in methylcobalamin for the investigation of biomethylation processes

In the environment, the methylation of metal(loid)s is a widespread phenomenon, which enhances both biomobility as well as mostly the toxicity of the precursory metal(loid)s. Different reaction mechanisms have been proposed for arsenic, but not really proven yet. Here, carbon isotope analysis can foster our understanding of these processes, as the extent of the isotopic fractionation allows to differentiate between different types of reaction, such as concerted (SN2) or stepwise nucleophilic substitution (SN1) as well as to determine the origin of the methyl group. However, for the determination of the kinetic isotope effect the initial isotopic value of the transferred methyl group has to be determined. To that end, we used hydroiodic acid for abstraction of the methyl group from methylcobalamin (CH3Cob) or S-adenosyl methionine (SAM) and subsequent analysis of the formed methyl iodide by gas chromatography (GC) isotope ratio mass spectrometry (IRMS). In addition, three further independent methods have been investigated to determine the position-specific δ (13)C value of CH3Cob involving photolytic cleavage with different additives or thermolytic cleavage of the methyl-cobalt bonding and subsequent measurement of the formed methane by GC-IRMS. The thermolytic cleavage gave comparable results as the abstraction using HI. In contrast, photolysis led to an isotopic fractionation of about 7 to 9‰. Furthermore, we extended a recently developed method for the determination of carbon isotope ratios of organometal(loid)s in complex matrices using hydride generation for volatilization and matrix separation before heart-cut GC and IRMS to the analysis of the low boiling partly methylated arsenicals, which are formed in the course of arsenic methylation. Finally, we demonstrated the applicability of this methodology by investigation of carbon fractionation due to the methyl transfer from CH3Cob to arsenic induced by glutathione.

The difference in stability between 5′R and 5′S diastereomers of 5′,8-cyclopurine-2′-deoxynucleosides. DFT study in gaseous and aqueous phase

Abstract Oxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts it has been decided to calculate the stability of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The calculations showed a significant negative enthalpy for glycosidic bond cleavage reaction for cationic forms and slightly negative for neutral ones. The preliminary study of the discussed process has shown the nature of stepwise nucleophilic substitution DN*AD type mechanism. Surprisingly, the different values in free energy, between short-lived oxacarbenium ion intermediates, have been found to lie over a relatively small range, around 1 and 2.8 kcal mol−1. For anions, the decomposition enthalpies were found as positive in aqueous phases. These theoretical results are supported by the formic acid hydrolysis experiments of both diastereomers of cdA, for the first time. (5′S)cdA exhibited higher stability than (5′R)cdA.

Synthesis of Optically Active Aromatic Ether Ketone Macrocycles Containing 2,2′-Dimethoxy-1,1′-binaphthyl-6,6′-diyl Moieties

Optically active aromatic ether ketone macrocycles containing 2,2′-dimethoxy-1,1′-binaphthyl-6,6′-diyl moieties were synthesized through electrophilic aromatic substitution reaction and stepwise nucleophilic aromatic substitution reactions. Structures of the resulting macrocycles were confirmed by NMR and matrix assisted laser desorption/ionization time of flight (MALDI-TOF) mass measurements.