Nitriles In Presence Research Articles

Изучение влияния температуры и продолжительности гидротермального воздействия на устойчивость акрилатных терполимеров

Dynamic light scattering, capillary viscometry, and IR-Fourier spectroscopy have been used to study the effect of temperature and duration of hydrothermal exposure on the chemical composition and structure of acrylate ionic terpolymers of acrylamide (AA), acrylonitrile (AN), and sodium salt 2- acrylamide-2-methylpropanesulfonic acid (AMPSNa) AA-AN- AMPSNa. It has been established that an increase in the duration and temperature of exposure increases the effect of thermo- hydrolysis on the colloidal characteristics of the terpolymer, namely, the average hydrodynamic size of the solvated macromo- lecular polymer coils decreases. A relationship has been established between the chemical composition and structure of the initial terpolymer and the chemical composition and structure of polymer fragments formed after hydrothermal exposure. It has been determined that the increase in stability during thermohydrolysis is associated with the presence of nitrile and sulfo- nate substituents in the side groups of the polymer chain. It has been shown that the AA and AN units of the acrylate terpoly- mer are primarily subjected to thermal treatment. A noticeable change in the composition of the terpolymer after thermohy- drolysis is observed for 5 hours at an exposure temperature of 180 °C, and for 3 hours at 200 °C.

Synthesis of Phosphinines from CoII-Catalyzed [2+2+2] Cycloaddition Reactions

The CoII-catalyzed [2+2+2] cycloaddition of functionalized diynes and phosphaalkynes resulting in the formation of an array of structurally interesting phosphinines is reported. A combination of 1,2-bis(diphenylphosphino)benzene (dppbenz) and CoI2 turned out to be the most suitable and active catalyst system under microwave reaction conditions. Chemoselective cyclizations of phosphaalkynes in the presence of nitriles have been observed, and a number of carbonyl functionalities are tolerated as well. The reaction can successfully be conducted with a 1:1 ratio of phosphaalkyne/diyne substrate. Model reactions with benzonitrile and diyne demonstrated that CoII catalysts in the presence of bisphosphines prefer carbocyclization, while reduction to lower oxidation states promotes heterocyclization to the corresponding pyridine. A reaction mechanism comprising a CoII oxidation state for the cyclotrimerization process is proposed and rationalized based on control experiments and theoretical calculations.

Base‐Catalyzed Hydrosilylation of Nitriles to Amines and Esters to Alcohols

AbstractBase‐catalyzed hydrosilylation of nitriles to amines and esters to silylated alcohols is reported. This protocol tolerates electron‐rich and electron‐neutral olefins and works in the presence of basic functional groups (e. g. tertiary amines) but fails for acidic substrates, such as phenols and NH anilines. This catalytic system does not tolerate carbonyl groups, such as aldehydes, ketones, esters and carbamides, which are reduced to corresponding alcohols and amines. With the exact amount of silane, esters can be selectively reduced in the presence of nitriles, but the selectivity drops for the pairs ester/carboxamide and carboxamide/nitrile. Through competition experiments, the following preference in functional group reactivity was determined: ester > carboxamide > nitrile.

Pd(II)-Catalyzed C═C Bond Cleavage by a Formal Group-Exchange Reaction

A chelation-assisted palladium-catalyzed C═C bond cleavage of α, β-unsaturated ketone to form alkenyl nitrile in the presence of nitrile is disclosed on the basis of a formal group-exchange reactio...

Regioselective 1,3-Dipolar Cycloaddition of Nitriles with Nitrile Imines Generated from Tetrazoles

Abstract A synthesis of 3,5-disubstituted-1,2,4-triazoles from nitriles and 5-aryltetrazoles is reported. When 5-aryltetrazoles are triflylated in the presence of nitriles, the resulting 5-aryl-2-triflyltetrazoles thermally generate N-triflyl-nitrile imines through a sequence of ring-chain tautomerization and denitrogenation. The N-triflyl-nitrile imines immediately undergo 1,3-dipolar cycloaddition with nitriles in a regioselective manner, forming the corresponding 1,2,4-triazoles.

Diazo Activation with Diazonium Salts: Synthesis of Indazole and 1,2,4-Triazole.

A donor/acceptor diazo activation strategy, processing via condensation using diazonium salts without the addition of any other catalysts or reagents, is reported. The diazenium intermediate was found to undergo cyclization to give indazoles in excellent yields. Alternatively, in the presence of nitriles, substituted 1,2,4-triazoles were obtained in good to excellent yields. This interesting diazenium route provides a new approach to achieve complex heterocycle synthesis under mild conditions.

A Gold‐Catalyzed Acid‐Assisted Regioselective Cyclization for the Synthesis of Polysubstituted Oxazoles

Polysubstituted oxazole derivatives are obtained through a regioselective gold‐catalyzed reaction of α‐alkynylamides and alkynoates in the presence of nitriles. The intermediary obtained gold carbenes are generated by alkyne oxidation with a pyridine N‐oxide. Acidic conditions ensure that only one of the two carbonyl oxygen atoms in these intermediates selectively cyclizes to the products in excellent yields.

Tetrazole Based Porous Metal Organic Framework (MOF): Topological Analysis and Dye Adsorption Properties

A tetrazole based metal organic framework [Cu(Metet)]n (MOF-1) (MetetH = 5-methyl-1H-tetrazole) has been prepared under solvothermal condition using sodium azide and nitrile in presence of CuCl2·2H2O. The crystalline product thus obtained was characterized by spectral (FTIR, UV–visible and fluorescence) and single crystal X-ray diffraction analysis. Tetrazole ligand is formed in situ by the reaction of azide and nitrile used. X-ray data confirm the tetrahedral geometry around the Cu(II) ion where all the four coordination sites are provided by four N of the four different ligand (Metet). MOF-1 has trigonal crystal system with R-3 m space group. Topological analysis of MOF-1 shows 4,4-c binodal net with uncommon ptr topology and stoichiometry, (4-c)(4-c). The detailed structural analysis reveals the porous nature of the MOF with channel of dimensions, Rf = 0.6 A and Rfi = 2 A. Further, the present MOF shows excellent adsorption properties towards organic dye, Methylene blue (MB) and thus can be employed as a good adsorbent for organic pollutants to remove MB from waste water. The possible rationale behind the dye adsorption is the porous nature of the MOF-1.

Oxidant‐Controlled Divergent Syntheses of Pyrazoles and Pyrroles by Copper(I)‐Catalyzed Oxidative Coupling of β‐Enamino Esters

AbstractCopper(I)‐catalyzed oxidative annulations of β‐enamino esters with oxidant dependence are disclosed. These reactions offer divergent syntheses of fully substituted pyrazoles and pyrroles from a common enamine substrate through sequential C−C and N−N or C−N bond‐forming reactions in the presence of nitriles as reagent or cosolvent. A mechanism involving radical intermediates generated by single‐electron transfer (SET) is proposed for both processes.

One Pot Synthesis of Biscoumarins and Pyranocoumarins by Coconut Juice as a Natural Catalyst

Background: The conception of ‘Green chemistry’ is the much inventive chemistry which is potent and more environmentally benign. It is notable that many organic reactions take place in conventional organic solvents, known as volatile organic compounds. Being concerned about the environmental impact, we report a promoting medium, coconut juice (ACC) for one-pot synthesis of biscoumarins and pyranocoumarins which is safe, harmless, green and environmentally benign. Methods and Results: Substituted biscoumarins have been achieved by the reaction of biscoumarin and substituted aromatic aldehydes in presence of ACC which acts as a green catalyst cum solvent. Each reaction showed good to excellent yield in presence of both electron donating as well as electron withdrawing group on aromatic aldehyde without formation of any by-products. Similarly, pyranocoumarins have been achieved by the reaction of biscoumarin, substituted aromatic aldehydes, active methylene nitrile in presence of ACC. All the reactions proceed smoothly and gave higher yields in case of malononitrile in comparison of ethyl-2-cyanoacetate. Conclusion: A simple, eco-friendly and novel procedure was demonstrated for the synthesis of biscoumarins and pyranocoumarins using natural feedstock coconut juice. The major importance of using ACC juice is higher yields, no work-up and no column chromatography.

Synthesis of multifunctional polymer containing Ni‐Pd NPs via thiol‐ene reaction for one‐pot cascade reactions

Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction.

Mn/Cu catalyzed addition of arylboronic acid to nitriles: Direct synthesis of arylketones

A direct and efficient synthesis of arylketones via arylboronic acid addition to nitriles in presence of inexpensive Mn/Cu catalytic system is reported. The use of non-precious Mn and Cu salts has been found to be highly advantageous both in terms of accessibility as well as cost effectiveness. A series of arylboronic acids as well as nitriles were used to synthesize a variety of symmetrical and unsymmetrical arylketones. Based on the literature studies, the reaction mechanism is anticipated to go through an aryl radical intermediate which reacted with the copper activated nitrile to give the desired arylketones after the hydrolysis of the imine intermediate.

Acid-Induced Reactions of 1,2-Oxaphosphetane Complexes

Selective P–O bond activation of 1,2-oxaphosphetane complexes [(OC)5W(P{CH(SiMe3)2}CH2CRR′O)] (R/R′ = H/H (1a), H/CH3 (1b), H/CF3 (1c), CF3/CF3 (1d)) was achieved using different Bronsted acids. In case of acids with nucleophilic anions, such as HCl and HBF4·OEt2, the corresponding halophosphane complexes [(OC)5W(XP{CH(SiMe3)2}CH2CRR′OH] (X = Cl (2a–c), F (3c,d)) resulted as ring-opened products; 2b could be closed again with tBuLi/12-crown-4. In contrast, trifluoromethanesulfonic acid could be used to initiate either a ring-opening hydrolysis with a subsequent cleavage of the P–M bond to yield PH(O){CH(SiMe3)2}{CH2C(CF3)2OH} (7) or, in the presence of nitriles, a ring expansion yielding [(OC)5W(P{CH(SiMe3)2}CH2CH2OCR═N)] (R = CH3 (5a), Ph (5b), C(CH3)3 (5c)). P–O bond cleavage in 1a was achieved using the Lewis acidic catechol(chloro)borane to give [(OC)5W(P{CH(SiMe3)2}CH2CH(CH3)OBcat}Cl)] (8; cat = catechol).

Atom-Economical Palladium Carbon-Catalyzed de Novo Synthesis of Trisubstituted Nicotinonitriles

A de novo palladium carbon-catalyzed synthesis of trisubstituted nicotinonitriles from easily synthesized homopropagylic or homoallylic aromatic alcohols in the presence of nitriles has been explored. The mechanism proceeds with an interesting generation of a Pd(II)-C palladacycle followed by an oxidative aromatization to generate the pyridine core. The pyridine core is generated with a noteworthy C-C bond cleavage in the case of the substituted nitriles. The moderate yields and easy separation of the products lend a unique importance to this one-pot methodology.

Photocatalytic reduction of nitro aromatic compounds to amines using a nanosized highly active CdS photocatalyst under sunlight and blue LED irradiation

AbstractA variety of aromatic nitro compounds were chemoselectively reduced to the corresponding anilines using conveniently prepared nanosized CdS as a photocatalyst under the sunlight and blue LED irradiation. The results demonstrated that synthesized CdS nanostructures have the potential to provide a promising visible light driven photocatalyst for chemoselective reduction of nitro aromatics in the presence of nitrile and carbonyl groups to the corresponding amines under both sunlight and blue LED irradiation. Photoreduction of nitro aromatics by the prepared nanosized CdS with high surface area was faster than when using the commercially available CdS under both sunlight and LED irradiation. Nanosized CdS photocatalyst was prepared by a simple method without any capping agent. X-ray diffraction (XRD), energy dispersive spectrometry (EDAX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N

Lewis acid mediated three-component one-flask regioselective synthesis of densely functionalized 4-amino-1,2-dihydropyridines via cascade Knoevenagel/Michael/cyclization sequence

A highly convergent and regioselective one-pot synthesis of hitherto unreported 4-amino-1,2-dihydropyridines has been achieved via three-component domino coupling (3CDC) of α-oxoketene-N,S-arylaminoacetals, aldehydes, and malononitrile in the presence of InCl3 under solvent-free conditions. The merit of this cascade Knoevenagel condensation/Michael addition/cyclization sequence is highlighted by its atom-economy, efficacy of forming consecutive three new bonds (two C–C and one C–N), and one ring in a single operation. Noteworthy, the presence of nitrile and amino groups at 3- and 4-positions of 1,2-dihydropyridine ring makes these compounds excellent precursors for further synthetic renovations. Remarkably, one of the newly synthesized 4-amino-1,2-dihydropyridine exhibited high selectivity and sensitivity for Fe3+ ion over other metal ions.

Exploration of relative chemoselectivity in the hydrodechlorination of 2-chloropyridines

The chemoselectivity of hydrodechlorination in 2-chloropyridine derivatives possessing reduction-sensitive functionalities is examined. The reaction conditions employed tolerate a variety of functionalities illustrating highly chemoselective hydrodechlorination in the presence of nitrile, allyl, terminal olefin, and nitroamine functionalities in excellent yield. Chemoselective deprotection of carboxybenzyl ethers is illustrated in moderate yield.

A versatile tripodal Cu(I) reagent for C-N bond construction via nitrene-transfer chemistry: catalytic perspectives and mechanistic insights on C-H aminations/amidinations and olefin aziridinations.

A Cu(I) catalyst (1), supported by a framework of strongly basic guanidinato moieties, mediates nitrene-transfer from PhI═NR sources to a wide variety of aliphatic hydrocarbons (C-H amination or amidination in the presence of nitriles) and olefins (aziridination). Product profiles are consistent with a stepwise rather than concerted C-N bond formation. Mechanistic investigations with the aid of Hammett plots, kinetic isotope effects, labeled stereochemical probes, and radical traps and clocks allow us to conclude that carboradical intermediates play a major role and are generated by hydrogen-atom abstraction from substrate C-H bonds or initial nitrene-addition to one of the olefinic carbons. Subsequent processes include solvent-caged radical recombination to afford the major amination and aziridination products but also one-electron oxidation of diffusively free carboradicals to generate amidination products due to carbocation participation. Analyses of metal- and ligand-centered events by variable temperature electrospray mass spectrometry, cyclic voltammetry, and electron paramagnetic resonance spectroscopy, coupled with computational studies, indicate that an active, but still elusive, copper-nitrene (S = 1) intermediate initially abstracts a hydrogen atom from, or adds nitrene to, C-H and C═C bonds, respectively, followed by a spin flip and radical rebound to afford intra- and intermolecular C-N containing products.

Mild and selective hydrogenation of aromatic and aliphatic (di)nitriles with a well-defined iron pincer complex.

The catalytic hydrogenation of carboxylic acid derivatives represents an atom-efficient and clean reduction methodology in organic chemistry. More specifically, the selective hydrogenation of nitriles offers the possibility for a green synthesis of valuable primary amines. So far, this transformation lacks of useful, broadly applicable non-noble metal-based catalyst systems. In the present study, we describe a molecular-defined iron complex, which allows for the hydrogenation of aryl, alkyl, heterocyclic nitriles and dinitriles. By using an iron PNP pincer complex, we achieve very good functional group tolerance. Ester, ether, acetamido as well as amino substituents are not reduced in the presence of nitriles. Moreover, nitriles including an α,β-unsaturated double bond and halogenated derivatives are well tolerated in this reaction. Notably, our complex constitutes the first example of an homogeneous catalyst, which permits the selective hydrogenation of industrially important adipodinitrile to 1,6-hexamethylenediamine.

B(C6F5)3-catalyzed Prins/Ritter reaction: a novel synthesis of hexahydro-1H-furo[3,4-c]pyranyl amide derivatives

The coupling of aldehydes or ketones with (2-(4-methoxyphenyl)-4-methylenetetrahydrofuran-3-yl)methanol in the presence of nitriles under the influence of 5mol% tris(pentaflourophenyl)borane at room temperature afforded a novel series of cis-fused hexahydro-1H-furo[3,4-c]pyran derivatives in good yields with high selectivity. This is the first report on the synthesis of hexahydro-1H-furo[3,4-c]pyranyl amide through a sequential Prins/Ritter reactions using B(C6F5)3 as a mild Lewis acid.