Density functional study of Diels-Alder reactions between cyclopentadiene and substituted derivatives of ethylene

Diels-Alder reactions of cyclopentadiene with ethylene, acrylonitrile, and acrolein were theoretically studied using density functional methods. The results obtained were compared with those corresponding to ab initio methods. Density functional methods, using the B-LYP nonlocal functional, or hybrid methods, yield energy barriers in excellent agreement with the experimental data. For the reactions with substituted derivatives of ethylene, the results show that acrylonitrile reacts with cyclopentadiene with virtually no stereoselectivity, while for acrolein, the formation of the endo product is predicted to be the most favorable from the values of activation Gibbs energies. © 1997 John Wiley & Sons, Inc.     

1,3-Dipolar Cycloaddition of 5-Substituted-1-Methyl-3-Oxidopyridiniums

5-Methoxy- and 5-dimethylamino-1-methyl-3-oxidopyridiniums were shown to give the 1,3-dipolar cycloadducts widely with methyl acrylate, acrylonitrile, N-phenylmaleimide, styrene, phenylacetylene, cyclopentadiene, cyclopentene, diethyl azodicarboxylate and singlet oxygen.     

含氨基酸侧链的有机硅高分子催化剂 Ⅵ.聚γ-(赖氨酸基)丙基硅氧烷钯催化剂的合成及加氢活性

合成了聚γ-(顿氨酸基)丙基硅氧烷钯催化剂当N/Pd摩尔比为3.4时,这种催化剂在常温常压下对丙烯腈的加氢活性高达3057·6mL H_2/min·mmolPd;对环戊二烯的氢化反应是分两步进行的。溶剂对催化剂的活性有明显影响。     

A rationalization of the solvent effect on the Diels-Alder reaction in ionic liquids using multiparameter linear solvation energy relationships

The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) having different hydrogen bond acceptor abilities has been carried out in several ionic liquids and molecular solvents in order to obtain information about the factors affecting reactivity and selectivity. The solvent effects on these reactions are examined using multiparameter linear solvation energy relationships. The collected data provide evidence that the solvent effects are a function of both the solvent and the solute. For a solvent effect to be seen, the solute must have a complimentary character; selectivities and rates are determined by the solvent hydrogen bond donation ability (alpha) in the reactions of acrolein and methyl acrylate, but not of acrylonitrile.     

Beziehungen zwischen der stereoselektivität zweier diels—alder-reaktionen und den molekularrefraktionen zahlreicher lösungsmittel

The relationships between the steroselectivities and molecular refractions of various solvents for two Diels—Alder reactions of cyclopentadiene and acrylonitrile or methyl acrylate are studied. Good correlations between log (N/X)-values and molecular refractions of solvents are observed. Accordingly, it can be said that polarizabilities of solvents are important factors for the stereoselectivities of the Diels—Alder reactions studied.     

Formation of molecular complexes in the diene synthesis reaction

Summary Using the spectrophotometric method it was shown that molecular complexes are formed in the diene synthesis reaction of acrolein, acrylic acid, acrylonitrile and methyl acrylate with cyclopentadiene and of SO₂ with 2,3-dimethyl-1,3-butadiene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimisheskaya, No. 7, pp. 1290–1292, July, 1965     

Effect of an α-Methyl Substituent on the Dienophile on Diels-Alder endo:exo Selectivity

A detailed computational study of the Diels-Alder reaction of cyclopentadiene with acrylonitrile, methylacrylate and their α-methylated counterparts methacrylonitrile and methyl methacrylate at the M06-2X(PCM)/TZVP level of theory has been performed. We want to understand the excellent exo-selectivities observed experimentally due the presence of this substituent. To this end, analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM-distortion interaction model) including solvation effects and NBO second order perturbation energy have been carried out.     

Studies on titanium organic compounds: VIII. Mechanism of vinyl polymerization in the presence of titanocene dichloride

The mechanism of catalytic polymerization of acrylonitrile in the presence of titanocene dichloride under light have been investigated by UV, NMR and ESR spectroscopy. Results of photochemical reaction monitored by UV and NMR showed that titanocene dichloride (Cp₂TiCl₂) in dimethyl sulfoxide system can be decomposed by light irradiation to give cyclopentadiene. ESR studies show that cyclopentadienyl free radical in photopolymerization system of Cp₂TiCl₂-acrylonitrile can be trapped by two kinds of spin trapping agents, phenyl-N-tert-butylnitrone and 2-methyl-2-nitrosopropane, respectively. Therefore, the radical mechanism of catalytic polymerization of acrylonitrile in the presence of Cp₂TiCl₂ under light is further confirmed.     

Diels-Alder reactions of cyclopentadiene and 9,10-dimethylanthracene with cyanoalkenes: the performance of density functional theory and Hartree-Fock calculations for the prediction of substituent effects

The activation enthalpies for the reactions of cyclopentadiene with ethylene, acrylonitrile, fumaronitrile, maleonitrile, vinylidene cyanide, tricyanoethylene, and tetracyanoethylene have been computed with the Hartree-Fock quantum mechanical method and a variety of density functionals (B3LYP, BPW91, and MPW1K) and compared to classic experimental data obtained by Sauer, Wiest, and Mielert (Chem. Ber. 1964, 97, 3183). Some significant errors in B3LYP activation enthalpies involving cyano groups, especially 3 or 4 cyano groups, have been identified, whereas HF and MPW1K reproduce substituent effects quite accurately.     

Synthesis of a novel bicyclic scaffold inspired by the antifungal natural product sordarin

A simplified bicyclic scaffold inspired by the antifungal natural product sordarin was designed and synthesized which maintains the carboxylic acid/aldehyde (or nitrile) pharmacophore. Docking studies with the target for sordarin, the fungal protein eukaryotic elongation factor 2 (eEF2), suggested that the novel scaffolds may bind productively. A densely functionalized chiral cyclopentadiene was constructed in 8 steps and utilized in a Diels-Alder reaction with acrylonitrile. The resulting [2.2.1] cycloheptene was transformed into a scaffold possessing vicinal carboxylic acid and nitrile groups, with orientations predicted to provide high affinity for eEF2. The synthetic approach disclosed here sets the stage for a renewed medicinal chemistry campaign against eEF2.     

A theoretical study of the solvent effect on Diels-Alder reaction in room temperature ionic liquids using a supermolecular approach

The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) in different room temperature ionic liquids containing imidazolium-based cations ([HBIM]⁺, [BMIM]⁺ and [BM₂IM]⁺) has been studied at the DFT level using a supermolecular approach. An analysis of the theoretical results shows that the ionic liquid cation coordination affects the equilibrium geometries and electronic structures of the reacting species throughout the reaction pathway leading to changes in reactivity and selectivity. They also indicate that the strong asynchronicity of the Diels-Alder reactions in ionic liquids is due to the polarisation effect of the cation.     

Solvent Effects on a Diels-Alder Reaction Involving a Cationic Diene: Consequences of the Absence of Hydrogen-Bond Interactions for Accelerations in Aqueous Media

In order to study the influence of hydrogen-bond interactions on the accelerations of Diels-Alder reactions in water and highly aqueous mixed solvent systems, second-order rate constants for the Diels-Alder reaction of acridizinium bromide (1a) with cyclopentadiene (CP) have been measured in aqueous media and organic solvents. Only modest rate accelerations were found in water-rich media. This is attributed to the absence of hydrogen-bonding groups in the reactants. Comparison with cycloadditions of CP with 9-carbomethoxyacridizinium bromide (1b), acrylonitrile (3), and methyl vinyl ketone (4), which do contain hydrogen-bond acceptors, reveals substantially larger aqueous accelerations. These results demonstrate that hydrogen bonding is a major factor in aqueous accelerations. Also rate constants for the cycloaddition of CP to 1a in surfactant solutions were determined. Micellar catalysis is observed in SDS solutions, due to binding of both the diene and the dienophile to the anionic micellar surface.     

Entrapment of cyclopentadiene in zeolite NaY and its application for solvent-free Diels-Alder reactions in the nanosized confined environment

Nonpolar cyclopentadiene was stably entrapped as a monomer in the hydrophilic supercages of zeolite NaY. A monomer form of cyclopentadiene in the supercages was confirmed by ¹³C MAS NMR spectroscopy. The adsorbed cyclopentadiene in the confined cavities performed the Diels-Alder reaction with typical dienophiles under solvent-free conditions more effectively than in organic and water media.     

烯酮及取代烯酮与环戊二烯环加成反应机理的理论研究

利用半经验分子轨道理论AM1方法,研究了烯酮及取代烯酮与环戊二烯环加成反应机理。采用Berny梯度法优化得到各反应的过渡态和中间体,并进行了振动分析确认。计算结果表明,该环加成反应是按照协同的非同步途径进行的,经过一个四元环发生扭曲的过渡态,并有部分电荷从环戊二烯迁移到烯酮或取代烯酮上,前线轨道分析表明反应机理为“2×[1+1]”机理;而氯甲基取代的烯酮与环戊二烯的环加成反应是按照分步途径发生的。计算结果可以很好地说明实验所观察到的立体选择性,并根据烯酮上取代基的电子效应和位阻效应对反应机理的影响进行了分析。     

On the reaction of hexafluoropropene with butadiene and cyclopentadiene

Reaction of hexafluoropropene with butadiene and cyclopentadiene in a stationary system was studied. The reaction of hexafluoropropene with burtadiene was shown to proceed along the scheme of [2+2]-cycloaddition, and with cyclopentadiene, as [2+4]-cycloaddition.     

2-烷基环戊-2-烯酮的简便合成新方法

2-位取代的环戊-2-烯酮是一类重要的有机合成中间体,它们的合成方法虽然已有不少文献报道,但大都路线较长,原料难得,条件苛刻且收率较低.本文报道一个以环戊二烯为原料,仅两步反应合成2-烷基环戊-2-烯酮的简便新方法. 以聚乙二醇(PEG)作为相转移催化剂,环戊二烯在氢氧化钾作用下与卤代烷在固-液相条件下反应,可方便地得到相应的烷基取代环戊二烯,主要为1-位和2-位烷基取代异构体的混合物.通过该方法制备烷基环戊二烯较之采用钠氨于液氨中反应的通常制备方法更可取.烷基环戊二烯进一步于甲醇中经溴代及酸性水解后,即可得到2-烷基环     

载体对环戊二烯在负载型钯催化剂上选择加氢的作用

制备了几种负载型的钯加氢催化剂, 考察了它们对环戊二烯加氢反应动力学行为的影响。环戊二烯对环戊烯的加氢有抑制作用, 抑制作用的主要原因是环戊二烯的配位能力远大于环戊烯, 催化剂的载体通过其配体效应可以影响两者配位能力之比(K_D/K_E)和反应速度常数之比(k_2/k_4), 从而改变催化剂的选择性和活性。     

One-pot synthesis of chiral bicyclo[3.3.0]octatrienes using diphenylprolinol silyl ether-mediated ene-type reaction

Chiral bicyclo[3.3.0]octatrienes with excellent enantioselectivity were synthesized from the simple starting materials of α,β-unsaturated aldehyde and cyclopentadiene via one-pot operation, which consisted of a diphenylprolinol silyl ether-mediated ene-type reaction, intramolecular addition reaction of cyclopentadiene moiety with aldehyde and dehydration reaction.     

取代苄基五甲氧羰基环戊二烯的合成和晶体结构

五甲氧羰基环戊二烯基钾和取代苄基卤化物反应, 合成了七个新型苄基取代五甲氧羰基环戊二烯。由^1H NMR、IR、元素分析等确认R(苄基)和环戊二烯上碳直接相连, 具有典型的碳碳连结。对产物之一, 1-萘亚甲基五甲氧羰基环戊二烯的X射线衍射测定, 进一步肯定了上述结论。化合物为单斜晶系, 空间群为P2/n, a=0.9731(1), b=1.7403(3), c=1.465(3)nm; β=95.70(1)^°, v=2.4712nm^3, D~c=1.334g/cm^3, 最终的R=0.093, 萘亚甲基环与环戊二烯基环的二面角为68.19^°。     

Synthesis of 5-vinyl-2-norbornene through Diels-Alder reaction of cyclopentadiene with 1, 3-butadiene in supercritical carbon dioxide

An efficient method for the synthesis of 5-vinyl-2-norbornene from cyclopentadiene and 1,3-butadiene was developed.The Diels-Alder reaction of cyclopentadiene with 1,3-butadiene proceeded smoothly in supercritical carbon dioxide in the absence of any polymerization inhibitor to produce the corresponding 5-vinyl-2-norbornene in satisfactory yield with high selectivity.