Carbon-nitrogen Double Bond Research Articles

Nitrogen-Nitrogen Radical Coupling-Enabled Precise Difunctionalization of Carbon-Nitrogen Double Bonds.

In this study, we have developed a metal-free, photoinduced energy transfer strategy for the efficient difunctionalization of carbon-nitrogen double bonds (C═N). Utilizing oxime ester-based bifunctional reagents, we have achieved direct radical difunctionalization of C═N bonds through nitrogen-nitrogen radical coupling, with over 35 examples and yields up to 96%. This method exhibits broad substrate scope, being compatible with a variety of carboxylic acids and biologically active molecules, thus offering a novel approach for the difunctionalization of heteroatom-containing unsaturated bonds in synthetic chemistry.

In(OTf)3-catalyzed one-pot synthesis of α-amido arylketazines

The one-pot synthesis of diversified α-amido arylketazines was developed under the oxygen atmosphere conditions. In(OTf)3-catalyzed benzylic oxidation of various α-arylacetamides followed by hydrazine (N2H4·2HCl)-mediated double condensation of the resulting α-ketoamides through the formation of two carbon-nitrogen double (CN) bonds. A plausible mechanism is proposed and well-discussed.

Integrated exploration of molecular structure, quantum chemical properties, molecular docking, and antioxidant activity of 4-(2-hydroxyanilino)pent-3-en-2-one

Schiff bases are crucial intermediates in organic chemistry. They are used to introduce carbon–nitrogen double bonds in organic molecules. In this study, 4-(2-hydroxyanilino) pent-3-in-2-one (L) was synthesized from the reaction of 2,4-pentanedione and 2-aminophenol. The structure of L was confirmed through analytical and spectroscopic data. In addition, its thermal stability was examined using thermogravimetric and differential thermal analysis. In the gas phase, investigations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) revealed an energy gap (ΔE) of 3.9304 eV. The antioxidant capacity of L was assessed using various techniques, including hydroxyl radical scavenging, scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene bleaching, and scavenging of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS). The synthesized Schiff base displayed significant antioxidant activity, with a half-maximal inhibitory concentration (IC50) of 19.8 µg/mL in the DPPH assay, 0.14 µg/mL in the ABTS assay, and 59.6 μg/mL in the hydroxyl radical scavenging assay. The bioactivity of the 4-(2-hydroxyanilino) pent-3-in-2-one was confirmed by the DFT study, and the MEP analysis indicates the reactivity of nitrogen and oxygen atoms. Docking studies and wave function analyses were conducted to provide further insights into the compound’s potential applications in the pharmaceutical field.

Stereoisomers of oxime ethers of 1,4-naphthoquinone: Synthesis, characterization, X-ray crystal structures, and DFT studies

In the present work, we use the C-3 substituted 2-hydroxy-1,4-naphthoquinones viz. 2-hydroxynaphthalene-1,4-dione (1), 2-hydroxy-3-methylnaphthalene-1,4-dione (2), and 2-chloro-3-hydroxynaphthalene-1,4-dione (3) as starting materials and obtained naphthoquinoneoxime ethers viz. 3-hydroxy-4-(methoxyimino)naphthalen-1(4H)-one (4), 3-hydroxy-4-(methoxyimino)-2-methylnaphthalen-1(4H)-one (5) and 2-chloro-3-hydroxy-4-(methoxyimino)naphthalen-1(4H)-one (6) via a facile and efficient synthesis involving condensation with methoxyamine hydrochloride. X-ray structure showed that 4 belongs to the orthorhombic (P212121) space group, whereas 5 and 6 (P21/c) crystalize in the monoclinic crystal system. The isomer ratios derived from NMR experiments elucidating stereoisomerism in compounds comprised of carbon-nitrogen double bonds have been analyzed; the naphthoquinone oxime ethers 4, 5, and 6 were also characterized employing the ωB97x-D/6–311++G (d, p) level of density functional theory. Theoretical studies reveal different conformational isomers with the ‘amphi’ and ‘syn’ isomers as low-lying structures along their energy hierarchy in accordance with the X-ray crystallography data. The spectral characterization of vibrational frequencies and 1H /13C NMR chemical shifts in unison with experiments and theory has been presented.

Borane-Trimethylamine Complex: A Versatile Reagent in Organic Synthesis.

Borane-trimethylamine complex (Me3N·BH3; BTM) is the most stable of the amine-borane complexes that are commercially available, and it is cost-effective. It is a valuable reagent in organic chemistry with applications in the reduction of carbonyl groups and carbon-nitrogen double bond reduction, with considerable examples in the reduction of oximes, hydrazones and azines. The transfer hydrogenation of aromatic N-heterocycles and the selective N-monomethylation of primary anilines are further examples of recent applications, whereas the reduction of nitrobenzenes to anilines and the reductive deprotection of N-tritylamines are useful tools in the organic synthesis. Moreover, BTM is the main reagent in the regioselective cleavage of cyclic acetals, a reaction of great importance for carbohydrate chemistry. Recent innovative applications of BTM, such as CO2 utilization as feedstock and radical chemistry by photocatalysis, have extended their usefulness in new reactions. The present review is focused on the applications of borane-trimethylamine complex as a reagent in organic synthesis and has not been covered in previous reviews regarding amine-borane complexes.

Asymmetric Allylation of Aldoxime Derivatives with β‐Amidoallylboronate in Water and Its Application to Divergent Synthesis of N‐Hydroxy‐γ‐Lactam and 1,2‐Oxazinan‐6‐one

AbstractA new application involving a water–stable amido–functionalized allylboronate has been developed for 1,2‐addition to carbon–nitrogen double bonds. The process achieves highly enantioselective allylation of aldoxime derivatives in water, by employing O‐Boc oximes as substrates under Zn(OH)2–chiral aminophenol catalysis. This process affords the corresponding homoallylic amines with 91–96 % ee. The products could be transformed into N‐hydroxy‐γ‐lactam or 1,2‐oxazinan‐6‐one, through an acidic or a protection‐acidic treatment sequence, respectively, almost without enantiopurity loss.

A Dual Functional Fluorescent Probe Based on Phenothiazine for Detecting Hg2+ and ClO- and its Applications.

For the efficient detection of Hg2+ and ClO-, a double-analyte-responsive fluorescent probe PTB was successfully synthesized by combining N-butyl-3-formyl phenothiazine with hydrazine benzothiazole, and designing a specific reaction site for recognizing two analytes (Hg2+ and ClO-) in a compound. It was shown that probe PTB successfully formed a stable complex with Hg2+ in the coordination ratio of 2:1 by using the strong sulfur affinity of Hg2+, which resulted in a remarkable "turn-off" effect, with a quenching efficiency of 92.5% and four reversible cycles of Hg2+ fluorescence detection. For the fluorescence detection of Hg2+, the response time is fast (≤ 2min) and the detection limit is low (7.8nM), showing extremely high sensitivity, and the performance is obviously better than that of the reported fluorescent probes for detecting Hg2+. In particular, probe PTB has low toxicity and good biocompatibility, and has been successfully used for imaging of Hg2+ in living cells. Moreover, probe PTB uses thioether bond and carbon-nitrogen double bond as reaction sites to detect ClO-, which has large Stokes Shift (149nm), good selectivity, high quenching efficiency (96.5%) and fast time response (about 10s), and successfully detects ClO- in actual water samples. The dual functional fluorescent probe PTB is sensitive for Hg2+ and ClO-. It has been successfully used for making pH fluorescent test paper and imaging detection of exogenous Hg2+ in VSMC cells with low toxicity.

Accelerated degradation and toxicity reduction of ribavirin by organic free radicals in the ferrate-acetylacetonate system

This study found that during the degradation of ribavirin (RBV) by ferrate (Fe(VI)) and acetylacetone (AA), organic free radicals significantly accelerated the degradation of ribavirin (RBV) and reduced the toxicity of degradation products. When [Fe(VI)]:[RBV] = 4:1, the pseudo 1st order rate constant of ribavirin removal increased 22.63 times compared with that without AA addition. Through quenching experiments, it was found that quenching of organic free radicals would reduce the degradation efficiency of RBV by 52.88%, while there was no significant effect on the degradation efficiency of RBV after ·OH and Fe(IV)/Fe(V) were quenched. Organic free radical addition products were found in the analysis of intermediate products of RBV degradation in Fe(VI)/AA system, which proved the existence of organic free radicals in Fe(VI)/AA system. Toxicity analysis by ECOSAR found that triazole was the most toxic intermediate product in the degradation process, and analysis of the electrophilic potential points by Dual descriptor found that the carbon-nitrogen double bond on triazole was the most susceptible position for electrophilic attack. The Laplacian bond order was analyzed and found that the addition of organic free radicals decreases the Laplacian bond order of the carbon-nitrogen double bond. The organic free radical (·CH3) generated in the Fe(VI)-AA system facilitated the degradation of RBV and accelerated the toxicity reduction by reducing the bond order of more toxic intermediates.

Developing a fast and catalyst-free protocol to form C=N double bond with high functional group tolerance.

The carbon-nitrogen double bond (C=N) is a fundamentally important functional group in organic chemistry. This is largely due to the fact that C=N acts as electrophilic synthon to give nitrogen-containing compounds. Here, we report the condensation of primary amine or hydrazine with very electron-deficient aldehyde to form C=N bond in the absence of any catalysts (metals and acids). The protocol performs at room temperature and applies water as co-solvent. Two hundred examples are presented here. With its intrinsic advantages of wide substrate scopes, excellent efficiency (high yields and short reaction time), operational simplicity, mild condition (room temperature as reaction temperature, no catalysts, no additions, water as co-solvent and opening to air) and available starting materials, the protocol can be compatible with various drugs, prodrugs, dyes and pharmacophores containing primary amino group. In addition, we also successfully apply this protocol to rapidly synthesize the core scaffolds of bioactive molecules.

Low-Temperature Gas-Phase Formation of Methanimine (CH2NH; X1A')─the Simplest Imine─under Single-Collision Conditions.

The D1-methanimine molecule (CHDNH; X1A')─the simplest (deuterated) imine─has been prepared through the elementary reaction of the D1-methylidyne (CD; X2Π) with ammonia (NH3; X1A1) under single collision conditions. As a highly reactive species with a carbon-nitrogen double bond and a key building block of biomolecules such as amino acids and nucleobases, methanimine is of particular significance in coupling the nitrogen and carbon chemistries in the interstellar medium and in hydrocarbon-rich atmospheres of planets and their moons. However, the underlying formation mechanisms of methanimine in these extreme environments are still elusive. The directed, low-temperature gas-phase formation of D1-methanimine will deepen our fundamental understanding of low-temperature molecular growth processes via carbon-nitrogen bond coupling. Considering the recent detection of the interstellar D1-methylidyne radical, the investigation of the CD-NH3 system also suggests a promising pathway for future astronomical observations of D1-methanimine as a molecular tracer of gas phase deuterium enrichment in deep space.

Functionalization of BODIPY Dyes with Additional C-N Double Bonds and Their Applications.

BODIPY (4-bora-3a,4a-diaza-s-indacene) dyes are regarded as highly useful compounds due to their rich photophysical properties, stability, and ease of functionalization. In recent years, hot topics studied with this class of compounds are targeted photodynamic therapy, photothermal therapy, fluorescent bioimaging agents, structural modification of the BODIPY core, synthesis of BODIPY analogs, and BODIPY-based supramolecular constructs. This review covers the advances in BODIPY structures substituted with additional carbon-nitrogen double bonds, namely imines, hydrazones, oximes, and related derivatives for various applications. Works based on fluorescent indicators of anions, cations, and neutral molecules are included in this review. In addition, the use of such structures for pharmaceutical applications, photodynamic therapy, fluorescent switches, and fluorescent building blocks are also investigated. In addition to covering the major literature within the mentioned subclass, design principles, working mechanisms, and outlooks are also provided to enlighten forthcoming promising efforts. With this work, we aim to provide insights about the synthesis, photophysical properties, contribution of C=N bonds to a class of dye, and possible areas of use and stimulate researchers to present new ideas and overcome the current problems using these derivatives.

Experimental and Computational Investigation of the Oxime Bond Stereochemistry in c-Jun N-terminal Kinase 3 Inhibitors 11H-Indeno[1,2-b]quinoxalin-11-one Oxime and Tryptanthrin-6-oxime.

11H-Indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) and tryptanthrin-6-oxime are potent c-Jun N-terminal kinase 3 (JNK-3) inhibitors demonstrating neuroprotective, anti-inflammatory and anti-arthritic activity. However, the stereochemical configuration of the oxime carbon-nitrogen double bond (E- or Z-) in these compounds was so far unknown. In this contribution, we report the results of the determination of the double bond configuration in the solid state by single crystal X-ray diffraction and in solution by 1D and 2D NMR techniques and DFT calculations. It was found that both in the solid state and in solution, IQ-1 adopts the E-configuration stabilized by intermolecular hydrogen bonds, in contrast to previously assumed Z-configuration that could be stabilized only by an intramolecular hydrogen bond.

A novel functional fluorescent probe based on a pyrene derivative for the detection of multiple pollutants

In regards to environmental protection, the detection of metal ions and pesticide residues remains meaningful and challenging. Herein, we report a novel multifunctional fluorescent probe based on a pyrene derivative, 4-[(pyren-1-ylimino)methyl]benzene-1,3-diol (PBD), that can recognize Al3+, Cr3+, Fe3+ and mesotrione with quantification of the sample being tested. In addition, the PBD probe can detect Hg2+ in a “turn-off” fluorescent mode. It is worth noting that the hydrolysis of carbon–nitrogen double bonds in the PBD Schiff base structure is targeted and catalyzed by Fe3+, Al3+ and Cr3+ cations, while mesotrione can also promote the hydrolysis of Schiff bases through the formation of intermolecular hydrogen bonds. Consequently, the PBD probe with weak fluorescence was converted to 1-aminopyrene in a localized state, showing stronger fluorescence. In addition, chelation may lead to fluorescence quenching of the PBD probe in the presence of Hg2+. The quantitative determination of Fe3+, Al3+, Cr3+ and mesotrione is achieved in which the limit of detection (LOD) is calculated to be 0.52, 0.30, 0.32 and 0.70 μM, respectively. Hg2+ detection is realized with an LOD of 1.93 μM. Moreover, the sensitive PBD probe is utilized to determine the amount mesotrione in actual water samples, demonstrating its potential practical applications. In addition, the multifunctional PBD probe can be employed for intracellular imaging of Fe3+ and Hg2+ based on its low cytotoxicity and certain water solubility. The present work describes a very competitive fluorescent probe for the detection of different types of pollutants, which is relevant to future research regarding environmental contaminant monitoring.

Polymerization of Aryl Polyisocyanides Catalyzed by N-Heterocyclic Carbene-Ligated Scandium Trialkyl Complex

Polyisocyanide has attracted continuous attention because of its stable helical rod structure and its wide application, it has a unique π-conjugated system in which the carbon-nitrogen double bond in each unit is twisted along the polymeric backbone to form a helical configuration. In this paper, a series of aryl isocyanides polymers are prepared using N-heterocyclic carbene-ligated scandium trialkyl complex 1 (IPr)Sc(CH2SiMe3)3 as the catalyst and 2 equiv. [Ph3C][B(C6F5)4] as the co-catalyst. The catalyst can convert 96% of 100 equiv. monomer in 5 minutes and the activity of the polymerization can reach 329 kg of polymer molSc-1 h-1. Two optically active polymers are obtained by using chiral monomers, they show strong CD signal at 364 nm and the two signals are opposite.

A fluorescence “turn-on” probe for the detection of HSO3− based on a pyrene-functionalized mesoporous silica material

An organic-inorganic hybrid mesoporous material PYA-SBA-15 was developed as a fluorescent probe for HSO3− with high selectivity and sensitivity, which was attributed to the Michael addition reaction between the carbon-nitrogen double bond and HSO3−.

A novel pyrene-based fluorescent probe for Al3+ detection

Based on the classical Schiff base reaction, fluorescent probe dimethyl 5-((pyren-1-ylmethylene)amino)isophthalate (PAI) is designed and synthesized through introducing Schiff base structure to pyrene unit for structural modification. The structure of the synthesized probe PAI is determined and characterized by FT-IR, 1H NMR, 13C NMR and HRMS. PAI is a type of “turn-on” probe which can specifically recognize Al3+ ion with high selectivity. The limit of detection is calculated to be 3.07 × 10−8 M, which proves the probe’s high sensitivity and is lower than that of many efficient reported probes. The probe PAI is intrinsically non-fluorescent due to the photoinduced electron transfer (PET) process. However, the addition of Al3+ ion leads to the breakage of the carbon–nitrogen double bond of Schiff base in PAI resulting in the product without PET property, which shows a typical localized state with enhanced fluorescence and blue color. In addition, PAI can recognize Al3+ ion through test papers, which is in favor of the future research regarding to Al3+ ion sensing.

A Plausible Mechanism for the Iridium-Catalyzed Hydrogenation of a Bulky N-Aryl Imine in the (S)-Metolachlor Process.

The hydrogenation of N-(2-ethyl-6-methylphenyl)-1-methoxypropan-2-imine is the largest-scale asymmetric catalytic process for the industrial production of agrochemical (S)-metolachlor. The challenging hydrogenation across the sterically crowded carbon–nitrogen double bond was achieved using a mixture of [IrCl(COD)]2, (R,SFc)-Xyliphos, NBu4I and acetic acid. Acetic acid was critical in achieving excellent productivity and activity. Despite its industrial significance, a mechanism that explains how the sterically hindered bond in the imine is reduced has yet to be proposed. We propose a plausible proton-first, outer-sphere mechanism based on density functional theory calculations that is consistent with the experimentally observed activity and the enantioselectivity of the industrial process. Key findings include transition states involving acetate-assisted dihydrogen splitting, and a hydride transfer from a five-coordinate iridium trihydride directed by a C-H∙∙∙Ir interaction. This article was submitted to a Special Issue in honor of Professor Henri Kagan.

Alkaloid Based Chemical Constituents of Ocimum santum & Cinchona Bark : A Meta Analysis

This article provides a concise summary of the recent developments that have been achieved in our comprehension of the asymmetric addition processes that are catalysed by native Cinchona alkaloids and their derivatives. This class of reactions includes cycloadditions, 1,4-adds, direct nucleophilic additions across carbon–oxygen or carbon–nitrogen double bonds, and direct nucleophilic additions across carbon–oxygen double bonds. Because of their capacity to catalyse the addition of a wide variety of functional groups to C9, many Cinchona alkaloids have been utilised in these processes as catalysts. These functional groups include amino, alkoxy, hydroxyl, amido, urea, and thiourea, among others. The importance of mechanical variables is emphasised in many different contexts. Additionally, the utilisation of adducts in future synthesis is sometimes broken down into its component steps. Ocimum basilicum was discovered to be mostly consisted of estragol (> 35.71 percent), (E)-ocimene (> 1.47 percent), trans-bergamotene (> 0.83 percent), a-cadinol (> 0.41 percent), eucalyptol (> 0.25 percent), and -caryophyllene (> 0.07 percent), whereas Ocimum sanctum is primarily composed of eucaly There is a greater concentration of chemical components in the leaves of Ocimum basilicum and Ocimum sanctum than there is in the actual inflorescence or flowers of the plant. The genetic distance between the two species was analysed in order to better understand the interspecies relationship, and the results showed that it was 2.86. The small difference in genetic makeup that exists between Ocimum basilicum and Ocimum sanctum is evidence that these two species are related to one another and share similar traits.

Monomeric silica supported interaction of TOSMIC with highly functionalized imines: A green approach to azetidines via ABB‐type cycloaddition reaction

AbstractThe reaction of TOSMIC with highly functionalized imines has been reported. The use of monomeric silica as a catalyst for the reaction has been reported for the first time. The main product of the reported green methodology, formed by the sequential attack of the two TOSMIC units upon the carbon–nitrogen double bond of highly functionalized imines, has been identified as bis(tosylmethyl)azetidine, a four member N‐heterocyclic system. The scope of the reaction concerning functionalized imines and TOSMIC reactivity has been studied and determined, keeping in view the advantage of using TOSMIC as component B for the ABB‐type cycloaddition reactions.

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity