Diels-Alder Reaction Of Cyclopentadiene Research Articles

Influence of Dispersion Interactions in the Diels-Alder Reaction of Cyclopentadiene, Anthracene and Tetracene with C60: A DFT Examination

Asbtract: The activation and thermodynamic parameters of the Diels-Alder reaction of cyclopentadiene, anthracene and tetracene with C60 fullerene are estimated at the DFT level using PBE0, B3LYP and CAM-B3LYP functionals and the effect of accounting for dispersion interactions in various semi-empirical Grimme models on these parameters. Structural characteristics of the reagents, products, pre-reaction van der Waals complex, and transition state are obtained. Taking into account dispersion corrections have practically no effect on the geometric characteristics of structures with the covalent type of the bond, as well as on the structure of the transition state. Still, it has a noticeable effect only on the structure of the pre-reaction complex, in which the interparticle interaction has a van der Waals character. At the same time, taking into account dispersion corrections plays a significant role in assessing the thermodynamic and activation parameters of the reaction. An analysis of the performed calculations showed that the combination of PBE0/def2-TZVP with the D4 model for dispersion interactions could be recommended for the Diels-Alder reaction considered above.

Experimental study on Diels-Alder addition of conjugated dienes directly from cracking C5 fraction by continuous micro-channel reactors

Diels-Alder reactions of cyclopentadiene, isoprene, and trans-1,3-pentadiene in the cracking C5 fraction with maleic anhydride were gradually carried out by step-heating in a continuous-settling reactor and a micro-channel reactor. Kinetic experiments (effects of temperature, reaction time, and molar ratio) and response surface analysis of three Diels-Alder reactions were carried out, and kinetic equations were fitted. The conditions of nadic anhydride preparation in a continuous-settling reactor, such as residence time and temperature, and that of 3/4-methyltetrahydrophthalic anhydride synthesis in a micro-channel reactor, such as temperature, feed ratio, and residence time, were optimized. The conversion rate of CPD to more than 92%, IP and T-PD to more than 97% has been achieved.

Roles of Lewis Acid Catalysts in Diels-Alder Reactions between Cyclopentadiene and Methyl Acrylate.

The Diels‐Alder reaction of cyclopentadiene with methyl acrylate catalyzed by AlCl3 has been theoretically investigated. M06‐2X level DFT calculations have shown that the formation of two C−C bonds is asynchronous in the cycloaddition both in the endo path and in the exo path, thus making a good contrast to the well‐known concept of [4+2] reactions based on the orbital symmetry arguments. It was found that the catalyst facilitates the cycloaddition and brings a higher endo selectivity in the highly asynchronous process, as compared with the reaction of the diene and the dienophile without the catalyst.

N-Vinyl and N-Aryl Hydroxypyridinium Ions: Charge-Activated Catalysts with Electron-Withdrawing Groups.

Charge-enhanced Brønsted acid organocatalysts with electron-withdrawing substituents were synthesized, and their relative acidities were characterized by computations, 1:1 binding equilibrium constants (K1:1) with a UV-vis active sensor, 31P NMR shifts upon coordination with triethylphosphine oxide, and in one case by infrared spectroscopy. Pseudo-first-order rate constants were determined for the Friedel-Crafts alkylations of N-methylindole with trans-β-nitrostyrene and 2,2,2-trifluoroacetophenone and the Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone. These results along with kinetic isotope effect determinations revealed that the rate-determining step in the Friedel-Crafts transformations can shift from carbon-carbon bond formation to proton transfer to the catalyst's conjugate base. This leads to an inverted parabolic reaction rate profile and slower reactions with more acidic catalysts in some cases. Electron-withdrawing groups placed on the N-vinyl and N-aryl substituents of hydroxypyridinium ion salts lead to enhanced acidities, more acidic catalysts than trifluoroacetic acid, and a linear correlation between the logarithms of the Diels-Alder rate constants and measured K1:1 values.

Role of ionic liquids on the selectivity and the rate of organic reactions: A computational approach

In the last years, ionic liquids have been used as substitutes to common solvents since they combine good solubility properties with small vapor pressures. Herein, the Diels-Alder reactions of cyclopentadiene (CP) with acrolein, methyl acrylate and acrylonitrile in ionic liquids ([Emim][N(Tf)2]), ([Hbim][N(Tf)2]) and ([Bmim][OTf]) have been modeled with density functional theory to explore the effect of ionic liquids on the endo selectivity in the adducts. Besides the hydogen bonding interactions between the cation and the diene in all the structures, endo transition structures are slightly better stabilized than exo transition structures because of the favorable interactions between the H's of the CP ring and the O's of the [N(Tf)2]- and [OTf]- anions of the IL's. In this study, B3LYP/6-31 + G* and M06-2X/6-31 + G* calculations have demonstrated that endo selectivity in the Diels-Alder reactions can be achieved in the presence of ionic liquids in agreement with experiments.

Recyclable iron(ii) caffeine-derived ionic salt catalyst in the Diels-Alder reaction of cyclopentadiene and α,β-unsaturated N-acyl-oxazolidinones in dimethyl carbonate.

Iron(ii) triflate was used in combination with caffeine-derived salts as recyclable catalysts for the Diels–Alder reaction run in dimethyl carbonate (DMC) as a green solvent. The catalyst was prepared as an ionic salt from a xanthinium salt and Fe(OTf)2. Various substrates including α,β-unsaturated carbonyl and N-acyloxazolidinone derivatives were reacted with cyclopentadiene using this recyclable catalyst. The use of a low catalyst loading (1 mol%) afforded high yields (up to 99%) of the corresponding cycloadducts. The recycling and the efficiency of the catalyst were demonstrated for several runs.

Iodine(III) Derivatives as Halogen Bonding Organocatalysts.

Hypervalent iodine(III) derivatives are known as versatile reagents in organic synthesis, but there is only one previous report on their use as Lewis acidic organocatalysts. Herein, we present first strong indications for the crucial role of halogen bonding in this kind of catalyses. To this end, the solvolysis of benzhydryl chloride and the Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone served as benchmark reactions for halide abstraction and the activation of neutral compounds. Iodolium compounds (cyclic diaryl iodonium species) were used as activators or catalysts, and we were able to markedly reduce or completely switch off their activity by sterically blocking one or two of their electrophilic axes. Compared with previously established bidentate cationic halogen bond donors, the monodentate organoiodine derivatives used herein are at least similarly active (in the Diels-Alder reaction) or even decidedly more active (in benzhydryl chloride solvolysis).

Boranes in Organic Chemistry 2. β-Aminoalkyl- and β-sulfanylalkylboranes in organic synthesis

<p>Problems on using of β-aminoalkyl- and β-sulfanylalkylboranes in organic synthesis are considered in this review. The synthesis of boron containing a-aminoacids by Curtius rearrangement draws attention. The use of β-aminoalkylboranes available by enamine hydroboration are described. Examples of enamine desamination with the formation of alkenes, aminoalcohols and their transformations into allylic alcohol are presented. These conversions have been carried out on steroids and nitrogen containing heterocyclic compounds. The dihydroboration of N-vinyl-carbamate and N-vinyl-urea have been described. Examples using nitrogen and oxygen containing boron derivatives for introduction of boron functions were presented. The route to borylhydrazones by hydroboration of enehydrazones was envisaged. The possibility of trialkylamine hydroboration was shown on indole alkaloids and 11-azatricyclo-[6.2.1<sup>1,8</sup>0<sup>2,7</sup>]2,4,6,9-undecatetraene examples. The synthesis of β-sulfanyl-alkylboranes by various routes was described. The synthesis of boronic thioaminoacids was carried out by free radical thiilation of dialkyl-vinylboronates. Ethoxyacetylene has been shown smoothly added 1-ethylthioboracyclopentane. Derivatives of 1,4-thiaborinane were readily obtained by divinylboronate hydroboration. Dialkylvinylboronates react with mercaptoethanol with the formation of 1,5,2-oxathioborepane derivatives. Stereochemistry of thiavinyl esters hydroboration leading to stereoisomeric β-sulfanylalkylboranes are discussed. Examples of radical thiilation of various structural types vinylboronates were presented. In particular, 1,3,2-dioxaborinanes and 1,3,2-dioxaborolanes, containing by boron atom vinyl-, propenyl-, isopropenylor isopropylidene substituents have been used. Thiilation has been achieved by use of alkylmercaptanes, as well as mercaptamine derivatives. Alkylmercaptanes were able to replace the bromine substituent in tris-(2-bromoctyl)-borane. Dialkylvinylborates have been added hydrosulfite with the formation of 2-boronoethane sulfuric acids. A lot of examples of radical thiilation of vinylboronic acid dialkyl esters with mercaptoacids are presented. Under the azaisobutyric acid dinitryle conditions thioglycolic, β-mercaptopropionic, 2-mercaptoamberic acids and their esters as well as cysteine were added. Vinyl-, propenyl- and isopropenyldioxaborolanes were also participated in the thiilation with the formation of acetic, propionic or amberic acid thioethanoboronates. The high reactivity of B,B,B-trivinyl-N,N,N-triphenylborazine in the reaction with thiophenol, leading to B-tris-(phenylmercaptoethyl)-N-phenylborazine was shown. The problems of asymmetric hydroboration leading to chiral β-sulfanylalkylboranes were discussed briefly. In particular, an example, including dihydro-thiophene hydroboration, leading to (+)-R-thiofan-3-yl-diisopinocamphenylborane, and the interaction with acetaldehyde with the formation of (+)-R-3-thiophanyl-diethoxyborane was implemented. The reaction with 3,4-dihydrothiapyrane proceeds analogously. A synthetic route to sulfono-norbornen-boronic acid esters by Diels-Alder reaction of cyclopentadiene with arylsulfanyl-vinylboronic acid esters has been discussed.</p>

Theoretical analysis of reactivity patterns in Diels-Alder reactions of cyclopentadiene, cyclohexadiene, and cycloheptadiene with symmetrical and unsymmetrical dienophiles.

The Diels-Alder reactions of cyclopentadiene, cyclohexadiene, and cycloheptadiene with a series of dienophiles were studied with quantum mechanical calculations (M06-2X density functional theory) and analyzed with the distortion/interaction model. The poor reactivities of cyclohexadiene and cycloheptadiene with dienophiles that give relatively synchronous transition states result from the substantial distortion required to achieve a transition state involving the formation of two bonds of the diene simultaneously. However, highly asynchronous or stepwise reactions result in less distortion of the diene and less differences in reactivities of different dienes. The transition state geometry of cyclopentadiene is less distorted in the asynchronous reaction with 1,1-dicyanoethylene compared to that with cis- and trans-1,2-dicyanoethylenes, which react through synchronous transition states.

Theoretical Study of Salt Effects on the Diels–Alder Reaction of Cyclopentadiene with Methyl Vinyl Ketone Using RISM-SCF Theory

Salt effects on the Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone are investigated using reference interaction site model self-consistent field (RISM-SCF) theory. The rate of the reaction is accelerated by adding LiCl to the water solvent. The structures of four transition states, endo-cis, endo-trans, exo-cis, exo-trans, were found by geometry optimization of the cyclopentadiene and methyl vinyl ketone complexes. The endo-trans structure shows the lowest energy in both water and LiCl solution. The activation barrier of the reaction in LiCl solution is lower than that in water, and the difference is in good agreement with that from experiments. The decrease in the activation barrier arises from destabilization of the reactant species. The salt effect of LiCl makes all species concerning the reaction unstable by the hydrophobic effect; however, the increased hydrophobic effect in the TS complexes is suppressed by making the hydrogen bond, which is stronger compared with the reactant methyl vinyl ketone.

Kinetic Study of the Diels-Alder Reaction of Cyclopentadiene with Bis(2-Ethylhexyl) Maleate

The kinetics of the Diels-Alder reaction of cyclopentadiene with bis(2-ethylhexyl) maleate has been studied at temperatures between 25 and 100 °C and at atmospheric pressure. The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. As a result, fitting line similar with the linear curve of the Arrhenius equation at 25, 30 and 40 °C. However, the fitting curve, at 60, 80 and 100 °C, tended towards the outside of the curve in the form of Arrhenius equation. The ratio of endo/exo was a slight change from increase of the reaction temperature.

ChemInform Abstract: The Effect of Alumina on the Diels-Alder Reactions of Cyclopentadiene with Menthyl Acrylate and Dimenthyl Fumarate.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Diels-Alder Reactions Catalyzed by Zeolites.

Abstract Various Zeolite catalysed Diels-Alder reactions of cyclopentadiene, cyclohexadiene and furan with less reactive dienophiles were studied. Exclusive endoselectivity was obtained with Ce-Y zeolite + anhydrous ZnBr2 for cyclopentadiene as well as cyclohexadiene Diels-Alder reactions.

ChemInform Abstract: Asymmetric Synthesis of 2-exo-Aminonorbornane-2-endo-carboxylic Acid Derivatives.

Abstract The Diels-Alder reaction of cyclopentadiene with N-acetyl-α,β-didehydroalaninate of (−)-cis-3-hydroxy isobornyl neopentyl ether yields the corresponding 2-endo(exo)-acetamido-5-norbornene-2-exo(endo)-carboxylates with total diastereofacial selectivity and with a preference for the cycloadduct with the ester group placed at the endo position. So this dienophile is complementary with the previously described (−)-menthyl N-acetyl-α,β-didehydroalaninate for the asymmetric synthesis of 2-aminonorbornane-2-carboxylic acids, since with the latter dienophile exo cycloadducts are preferably obtained with a high diastereofacial selectivity.

ChemInform Abstract: Diels-Alder Reactions in Aqueous Solutions. Enforced Hydrophobic Interactions Between Diene and Dienophile.

Second-order rate constants and isobaric activation parameters for the intermolecular Diels-Alder reactions of cyclopentadiene with alkyl vinyl ketones (2a,b) and 5-substituted-1,4-naphthoquinones (3a-c) as well as for the intramolecular Diels-Alder reaction of N-furfuryl-N-methylmaleamic acid (4) were determined in water, monohydric alcohols, and highly aqueous solutions containing monohydric alcohols and other organic cosolvents. The intermolecular as well as the intramolecular Diels-Alder reaction are characterized by large rate accelerations upon going from an organic solvent to water as the reaction medium. A model for solvation effects on rate constants for Diels-Alder reactions in aqueous solutions is developed. The typical, huge rate enhancements for Diels-Alder reactions in water and in highly aqueous binary mixtures are significantly sensitive to substituent effects and are discussed in terms of enforced pairwise hydrophobic interactions between diene and dienophile.

ChemInform Abstract: Asymmetric Induction in the Diels-Alder Reaction of Cyclopentadiene with Acrylates of Cyclopentadiene with Acrylates of O-Methyleneacetals of Arabinose and Ribose.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Synthesis of a Highly Substituted Cyclopentane: Completely Exo- and Face-Selective Diels-Alder Reaction of Cyclopentadiene with Cyclic Sugar Dienophiles.

ChemInform Abstract: Synthesis of a Highly Substituted Cyclopentane: Completely Exo- and Face-Selective Diels-Alder Reaction of Cyclopentadiene with Cyclic Sugar Dienophiles.

ChemInform Abstract: Effect of Clay Calcination on Clay-Catalysed Diels-Alder Reactions of Cyclopentadiene with Methyl and (-)-Menthyl Acrylates.

ChemInform Abstract: Effect of Clay Calcination on Clay-Catalysed Diels-Alder Reactions of Cyclopentadiene with Methyl and (-)-Menthyl Acrylates.

ChemInform Abstract: Evaluation of Lewis Acidity of “Naked” Lithium Ion Through Diels-Alder Reaction Catalyzed by Lithium TFPB in Nonpolar Organic Solvents.

The Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone was remarkably promoted by anhydrous LiTFPB as a Lewis acid catalyst both in dichloromethane and in toluene. Experimental and computational investigations revealed the effects of solvent, hydrating water molecules, and counter anions on the Lewis acidity of the “naked” lithium ion.

ChemInform Abstract: Bisoxazoline and Bioxazoline Chiral Ligands Bearing 4-Diphenylmethyl Shielding Substituents. Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone Catalyzed by the Aqua Nickel(II) Complex.

Enantiopure 2-amino-3,3-diphenyl-1-propanol has been synthesized by the hidantoin route starting from diphenylacetaldehyde, followed by subsequent functional group transformations and optical resolution by a chiral HPLC. This amino alcohol can be converted into two new chiral ligands: 4,4′-bis(diphenylmethyl)-2,2′-bioxazoline and 2,2′-isopropylidenebis(4-diphenylmethyloxazoline), and further to complexes with copper(II) trifluoromethanesulfonate and nickel(II) perchlorate hexahydrate. The nickel(II) aqua complex derived from the bisoxazoline effectively catalyzes the Diels-Alder reactions of cyclopentadiene with 3-acryloyl-2-oxazolidinone in high endo-selectivities and moderate enantioselectivities through a square planar transition structure.