CN Double Bond Research Articles

Synthesis, characterization, crystal structure determination and computational study of the two new bidentate O, N Schiff bases derived from bromosalicylaldehyde and amines containing alkyl halide pendant groups

Two new Schiff base compounds 2-{(E)-[2-(bromoethyl)imino]methyl}-4-bromophenol (1) and 2-{(E)-[2-(chloroethyl)imino]methyl}-4-bromophenol (2) have been synthesized and characterized by FT-IR and 1H NMR spectroscopy, elemental analysis, thermal studies and single-crystal X-ray diffraction. They crystallize in the triclinic system, space group P−1. Both Schiff base compounds 1 and 2 display a trans configuration with respect to the CN double bond. Quantum theory of atoms in molecules (QTAIM) has been also used to find intramolecular interactions and investigate their chemical nature. The results show that in both of the compounds 1 and 2, there is a hydrogen bonding between nitrogen of imine and oxygen of phenol which is considerably stronger than normal hydrogen bonds. In addition, it has been shown that these hydrogen bonds are partially covalent and partially electrostatic in nature, in contrast to normal hydrogen bonds, which are usually considered as electrostatic interactions.

Synthesis, stereochemical, structural and biological studies of some 2,6-diarylpiperidin-4-one N(4′)-cyclohexyl thiosemicarbazones

A new series of 2,6-diarylpiperidin-4-one N(4′)-cyclohexyl thiosemicarbazones (13–23) were synthesized by corresponding 2,6-diarylpiperidin-4-ones (1–11) reaction with cyclohexyl thiosemicarbazide (12). The chemical structures were confirmed by means of IR, one and two dimensional NMR, Mass spectra and single crystal X-ray diffraction analysis. Compounds 13–23, exist in chair conformation with equatorial orientation of all the substituents at piperidine ring except the methyl group at C-5 of compounds 21–23 oriented at axial disposition to stabilize the chair conformation. Single crystal X-ray structural analysis of compound 18, evidences that the configuration about CN double bond is syn to C-5 carbon (E-form). All the synthesized compounds were screened their biological activity.

Reversible trans–cis photoisomerization of new pyrrolidene heterocyclic imines

A series of novel pyrrolidene imines bearing functionalized aryl or naphthyl moieties was synthesized and their photochromic properties studied by UV spectroscopy. UV irradiation of these heterocyclic Schiff bases at room temperature promotes the trans–cis photoisomerization of the CN double bond with formation of a variable amount of the cis-isomer that, in the absence of light, returns thermally to the original form in few seconds. The thermal cis–trans re-isomerization of these molecular switches is much more slower than for the common benzylidene aniline-type imines, allowing the observation of the photochromic phenomena at room temperature. Strong electron-donor substituents in the para-position of the aniline part of the molecule decreases even more the kinetics of the thermal cis–trans re-isomerization leading to a manifest change in the UV spectrum.

Green synthesis and catalytic properties of polyallylamine functionalized tetrahedral palladium nanocrystals

The water-soluble polyallylamine (PAH) functionalized tetrahedral palladium nanocrystals with adjustable size and concavity are successfully achieved through a one-pot hydrothermal synthesis. The size, morphology and surface composition of tetrahedral palladium nanocrystals are investigated by transmission electron microscopy (TEM), high angle annular dark field scanning TEM (HAADF-STEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The anchorage of PAH on palladium nanocrystals results in excellent colloidal stability and anti-oxidation capability of palladium nanocrystals. Both {110} and {111}-enclosed concave tetrahedral palladium nanocrystals (c-Pd-TNCs) exhibit superior catalytic activity to only {111}-enclosed flat tetrahedral palladium nanocrystals (f-Pd-TNCs) for the hydrogenation reduction of nitro functional groups and CN double bond.

The nature of the styrylindolium dye: transformations among its monomer, aggregates and water adducts

The optical properties of styrylindolium dyes are strongly influenced by the external environment. After a detailed investigation by electronic absorption spectroscopy, we found that five states of 2-methoxylstyryl-indolium dye viz. monomer, D-aggregate, H-aggregate, J-aggregate and water adducts can be observed under different conditions. The spectroscopic studies revealed that the conversion rate of the dye among its monomer and the other aggregates is slow due to the steric hindrance of the 3,3-dimethyls. Meanwhile, it could form water adducts by the reaction of the water residue in solvent with the charged electron-deficient CN double bond of the dye. The formation of water adducts is also an important factor that influences the optical properties of the dye because the water addition reaction breaks the dye's π-conjugate. Generally, the dye exists mainly in the monomeric form in freshly prepared solutions. A small portion of the D-aggregate, H-aggregate and J-aggregate can be observed in some cases. In equilibrium solutions, however, significant changes are observed in most solvents with different polarities. The J-aggregate is an unstable state which is irreversibly converted to other species. The monomer converts reversibly among the D-aggregate, H-aggregate and water adducts in the equilibrium state. At the same time, the water adducts are sensitive to the external environment and their content can be modulated by temperature and pH conditions. The dye's prominent optical signal changes arising from pH- and thermal dependence of water addition or the disassociation of the D-aggregate led to potential applications in the field of thermoresponsive probes under given conditions.

Water-controlled chiral inversion of a nitrogen atom during the synthesis of diaziridines from α-branched N,N'-dialkyl α-diimines

Desymmetrization of chiral α-diimines by ethyl nosyloxycarbamate using water as a co-solvent takes place with very high diastereoselectivity, the nucleophilic attack occurring only on the less hindered side of the CN double bond. Interestingly, the presence of water in the reaction medium likely stabilizes the anion intermediate slowing down the successive cyclization reaction and favoring the rotation around the C–N single bond. In fact, as confirmed by ROESY experiments, only the two diastereomeric 3-(iminomethyl)diaziridine-1-carboxylates that differ in the absolute configuration of the alkyl substituted nitrogen atoms were always obtained in equimolar ratios. Finally, all compounds were easily obtained in optically pure form through HPLC separation and can be considered as interesting chiral synthons.

Characterization and controlled release aloe extract of collagen protein modified cotton fiber

For exploiting the novel multifunctional cotton fibers, a collagen protein modified cotton fiber (CPMCF) was prepared by the oxidation of cotton fiber with sodium periodate solution and subsequent crosslinking reaction with an aqueous solution of collagen protein in acetic acid. Infrared spectra and X-ray photoelectron spectrometry (XPS) analysis of the CPMCF illuminated that the CN double bond was formed through the imine reaction of the aldehyde group on oxidized cotton fiber with the amino group of collagen protein. X-ray diffractograms indicated that the crystallinity of the oxidized cotton fiber increased from 65.6 to 69.3% after collagen protein treatment. Scanning electron microscopy photographs displayed that the collagen protein combined on the surface of oxidized cotton fiber. The resulting optimum conditions to prepare the CPMCF achieved the sufficient aldehyde groups in oxidized cotton fiber and the collagen protein content on CPMCF, whereas the mechanical strength of the oxidized cotton fiber had no significant change. Meanwhile, a model experiment for the controlled release of aloe anthraquinone extract on CPMCF showed a satisfactory result compared with those release of the original cotton fiber, demonstrated potential application of the synthetic collagen protein–cotton fiber as a carrier for the sustained release of drugs.

The synthesis, crystal structure and enhanced blue fluorescence emission of novel antipyrine derivatives

Four new antipyrine derivatives were synthesized and characterized by elemental analysis, FT–IR, 1H NMR, 13C NMR spectroscopy, and a representative compound 1b was confirmed based on the X-ray crystallographic analysis. The antipyrine–phenylboronic acid 1b crystallizes in the monoclinic space group P21/c, and displays an E configuration about the CN double bond. The absorption and fluorescence spectra of these compounds were investigated. Replacement of a six-membered phenyl group with a five-membered thienyl unit in the antipyrine derivatives resulted in a bathochromic shift approximately 21nm, while the bithienyl system caused a strong bathochromic effect of 53nm relative to the substituted phenyl groups. The bithienyl-antipyrine hybrid 1c displayed a turn-on fluorescence response to water, acetic acid (HOAc) and sulfuric acid (H2SO4) in ethanol solution, but no fluorescence response toward alkali. Whereas the free compound was very weakly fluorescent in ethanol, the addition of water, HOAc and H2SO4 leads to an appearance of strong blue fluorescence and a dramatic increase of emission intensity.

The influence of substituent effects on spectroscopic properties examined on benzylidene aniline-type imines

Six selected benzylidene aniline-type prochiral imines were characterised by means of ATR-IR, UV–vis and Raman spectroscopy. A detailed UV–vis spectroscopic study supported by data obtained from single crystal X-ray analysis reveals the influence of the conformation of the imine on the electronic state. Additionally, the electronic effects of the substituents located in 4,4′-position on the shape of the UV–vis spectra were discussed. The influence of the substituents on the vibrational state of the CN double bond has been studied by ATR-IR spectroscopy using solid and dissolved samples. Finally, solvatochromatism and solvent-introduced tautomerism have been investigated by UV–vis and Raman spectroscopy. The effect of inter- and intramolecular hydrogen bond formation was demonstrated by changes of characteristic bands in the spectra.

Single stranded helical chains of C–H⋯π interactions further connected by halogen–halogen interactions of type I to construct supramolecular structure of (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound

In this study, (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound was investigated from the point of stacking interactions assembling the supramolecular network, conformational isomerism and tautomerism. For this purpose, X-ray diffraction, FT-IR and UV/Vis spectroscopic techniques were used, giving the following structural and spectroscopic properties of the compound: The title compound has two conformers (anti and eclipsed) in the crystal structure resulting from rotation about C–N single bond of ethyl group. Both conformers prefer enol form in the solid state, adopting E configuration about the CN double bond. The supramolecular architecture of the compound is constructed by two non-covalent interactions as C–H⋯π and halogen–halogen interactions. The repetition of C–H⋯π interactions is resulted in a single-stranded helical structure. The helical structures are further connected by C–I⋯I–C interactions of Type I to construct the two dimensional supramolecular network defined as (6,3)-net in Wells nomenclature. The title compound adopts both enol and keto forms in EtOH (a polar and protic solvent) while enol form is preferred in the solid state.

In situ preparation of composite from conjugated polyschiff bases and multiwalled carbon nanotube: Synthesis, electrochromic, acidochromic properties

Polyschiff base (PSB) which has the structure of CN double bond is well known as conducting material with high thermal resistance, chemical and electrical properties. Recently, it was used as hole transporting material in organic light emitting diode (OLED), chemical sensor and electrochromic materials. Carbon nanotubes (CNTs) with excellent properties such as unique electrical, mechanical, optical and chemical properties are promising reinforcing materials for polymer composites which improve the comprehensive properties of polymers. In this paper, conjugated PSB-grafted multiwalled carbon nanotubes (MWNTs) composite was prepared by in situ polymerization. The resultant composites were characterized by thermogravimetric (TGA), scanning electron microscopy (SEM), UV–vis absorption, photoluminescence (PL), cyclic voltammograms (CV), infrared spectroscopy (IR) and Raman spectroscopy. The composites exhibited high thermal stability and excellent reversibilities of electrochromic, photochromic, acidochromic characteristics, with the color change from the light yellow to blue.

ChemInform Abstract: Unprecedented Intramolecular [3 + 2] Cycloadditions of Azido‐Ketenimines and Azido‐Carbodiimides. Synthesis of Indolo[1,2‐a]quinazolines and Tetrazolo[5,1‐b]quinazolines.

AbstractA series of azido‐ketenimines (V) and azido‐carbodiimines (XII) is prepared.

Photochromism of (E)-4-phenyl-1-(pyridine-2-ylmethylene)semicarbazide

A photochromism molecule, (E)-4-phenyl-1-(pyridine-2-ylmethylene)semicarbazide (1), was reported. Photochromism of 1 in solution was shown to result from the trans–cis photoisomerization of its CN double bond, by using absorption, 1H NMR (including 2D NOESY) and directly the crystal structure of 1 obtained from solutions before and after UV irradiation. Photochromism of 1 in the solid state was found to take place, too, but via changes in the molecular geometry and packing upon UV irradiation.

Mono-, Tetra- and octanuclear transition metal complexes of in situ generated schiff base ligands containing up to 12 coordinating atoms: syntheses, structures and magnetism

By the reaction of an alkoxyl containing tetraamine, 1,3-bis[(2-aminoethyl)amino]-2-propanol, with various aldehydes, O-vanillin and 2,6-diformyl-4-cresol, in the presence of various metal cations, four novel complexes were synthesized and structurally characterized. Complexes [CoHL1](ClO4)·2MeOH (1) and [NiH2L2](ClO4)2·0.5MeOH (2) have mononuclear structures, with the linear di-Schiff base ligand (HL1)2− and mono-Schiff base ligand H2L2 generated from in situ reactions under various pH conditions. In complexes [Ni4L3(SCN)3(MeOH)]Cl·2.5MeOH (3), and [Cu8(H2L3)2(OH)4(ClO4)](SCN)6(ClO4)·8H2O (4), an interesting 32-membered dodecadentate macrocyclic ligand H4L3 comprising four Schiff base CN double bonds was generated by a “2+2” type condensation reaction between the tetraamine and the dialdehyde. Complex 3 has a tetranuclear Ni4 coordination structure with all 12 coordinating atoms of (L3)4− utilized for coordination, and the alkoxyl groups are deprotonated and coordinated in a bridging mode. Complex 4 exhibits an octanuclear Cu8 coordination structure, with a ClO4− bridging two tetranuclear [Cu4H2L3(OH)2]4+ moieties through four weak axial Cu–O coordination bonds. In complex 4, only 10 coordinating atoms of (L3)4− are utilized for coordination, with the two alkoxyl groups left neutral and noncoordinated. It is noteworthy that H4L3 has two long saturated chains in the molecule. Therefore, it has good flexibility and tends to have a nonplanar structure. Variable temperature magnetic data for 3 and 4 indicated the existence of antiferromagnetic interactions, which were discussed based on the structural results.

Asymmetric synthesis of α-amino boronate esters via organocatalytic pinacolboryl addition to tosylaldimines

Organocatalytic nucleophilic pinacolboryl addition from in situ generated MeO(-)→ B(2)pin(2) to C=N double bond can be performed enantioselectively with the aid of chiral phosphines, which promote enantiofacial differentiation in the course of the C-B bond formation.

ChemInform Abstract: Cycloaddition of Benzothiete and Electron-Deficient Nitriles.

The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.

ChemInform Abstract: Two Practical and Efficient Approaches to Fluorinated and Nonfluorinated Chiral β-Imino Sulfoxides.

Reaction of fluorinated and nonfluorinated N-substituted imidoyl chlorides 1 with lithium derivatives of enantiopure methyl p-tolyl sulfoxide 2a (or racemic methyl phenyl sulfoxide 2b) gave a wide variety of chiral N-substituted β-imino sulfoxides 4 in good to excellent yields. The title compounds (R)-4 were also prepared by aza-Wittig reaction of γ-fluoro-β-keto sulfoxides (R)-5 and N-aryl iminophosphoranes 6. The imino−enamino equilibrium was studied, showing, in all instances, the imino form as the predominant tautomer independent of the nature of the N-substituent. The configuration of the CN double bond was found to be Z for both N-alkyl and N-aryl derivatives on the basis of 1H NMR NOE difference experiments performed over several compounds. Ab initio calculations (HF/6-31G*) carried out on several representative examples of 1 and 4 are, in general, consistent with the experimental results.

ChemInform Abstract: Electrophilic and Nucleophilic Reactivities of the Azomethine Carbon of SAMP-Hydrazones: Stereoselective Synthesis of γ-Amino Ketone Derivatives.

A novel methodology for the asymmetric synthesis of secondary N-Boc-protected γ-amino ketones is described. After the highly diastereoselective nucleophilic 1,4-addition of formaldehyde SAMP-hydrazone 1 to prochiral conjugated enones 2, the carbonyl group of the resulting 4-oxo aldehyde SAMP-hydrazones 4 was protected as ethylene ketals 5. The stereoselective (de 58−88%) addition of organometallic reagents to the CN double bond of the latter was then performed, and the unstable intermediate hydrazines obtained were either trapped as Moc-protected hydrazines 8 in good yields (65−87%) or reduced by Raney nickel-catalyzed hydrogenolysis of the N−N bond to afford the corresponding amines, which were isolated as their corresponding N-Boc derivatives 11. Noteworthy, the azomethine carbon of SAMP-hydrazones, not being essentially modified during the process, sequentially serves as a nucleophilic and an electrophilic center, acting as a nexus between the conjugated enone (electrophile) and the organometallic reag...

2+2] Cycloaddition of electron-poor acetylenes to (E)-3-dimethylamino-1-heteroaryl-prop-2-en-1-ones: synthesis of highly functionalized 1-heteroaroyl-1,3-butadienes

Microwave-assisted [2+2] cycloaddition of (E)-3-dimethylamino-1-heteroaryl-prop-2-en-1-ones to dimethyl acetylenedicarboxylates gives (2E,3E)-dimethyl-2-[(dimethylamino)methylene]-3-(substituted)succinates in 8–91% yield. In the case of a 4,5-dihydrothiazoline derivative, cycloaddition also took place at the endocyclic CN double bond.

Facile construction of the guanidine substituent or guanidinate anionic ligand through addition of the adjacent amino group to carbodiimide

The reaction of N,N'-dicyclohexylcarbodiimide (DCCI) with [Cp(2)Yb(o-H(2)NC(6)H(4)S)](2) (Cp = C(5)H(5)) () forms the monomer product Cp(2)Yb[SC(6)H(4)N[double bond, length as m-dash]C(NHCy)(2)] (), indicating that the adjacent NH(2) group can add to the C[double bond, length as m-dash]N double bonds of carbodiimide to construct a neutral guanidine group. When DCCI reacts with [Cp(2)Y(o-H(2)NC(6)H(4)S)](2).2THF (), a dimer product [CpY(mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NHCy)NCy)(THF)](2) () was isolated, through the amino group addition and cyclopentadienyl elimination. Interestingly, on treatment of with one or two equivalent of (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr at the same conditions gave an amino group partial addition product CpY(THF)[mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NH(i)Pr)N(i)Pr)](mu-eta(2):eta(1)-SC(6)H(4)NH(2))YCp(2).THF (), where only one NH(2) group can add to the C[double bond, length as m-dash]N double bonds of carbodiimide molecule, another one is remained. However, when we extended this reaction to the gadolinium complex, a novel co-crystalline compound {Cp(2)Gd[SC(6)H(4)N[double bond, length as m-dash]C(NHCy)(2)]}.{CpGd(THF)[mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NHCy)NCy)][mu-eta(2):eta(1)-SC(6)H(4)NH(2)]GdCp(2).THF} () was obtained from the reaction of [Cp(2)Gd(o-H(2)NC(6)H(4)S)](2) () with DCCI. In order to investigate the sequence of addition and the elimination of the cyclopentadienyl group, a deprotonation reaction of the addition product has also been studied. Reaction of CpYb[SC(6)H(4)NC(NH(i)Pr)(2)](2)(THF) (), formed by reaction of Cp(3)Yb with two equivalent of o-aminothiophenol, and subsequently with 2 equiv. of (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, with one equiv. of Cp(3)Yb gave a cyclopentadienyl elimination product [CpYb(mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NH(i)Pr)N(i)Pr)(THF)](2) (). This result reveals that addition of the NH(2) group to carbodiimide is prior to the elimination of cyclopentadienyl group. All of new compounds have been characterized by elemental analysis and spectroscopic properties. The solid-state structures of complexes , and were determined by single-crystal X-ray diffraction.