Catalyzed Diels-Alder Reaction Research Articles

Scalable and Highly Diastereo- and Enantioselective Catalytic Diels-Alder Reaction of α,β-Unsaturated Methyl Esters.

Despite tremendous advances in enantioselective catalysis of the Diels-Alder reaction, the use of simple α,β-unsaturated esters, one of the most abundant and useful class of dienophiles, is still severely limited in scope due to their low reactivity. We report here a catalytic asymmetric Diels-Alder methodology for a large variety of α,β-unsaturated methyl esters and different dienes based on extremely reactive silylium imidodiphosphorimidate (IDPi) Lewis acids. Mechanistic insights from accurate domain-based local pair natural orbital coupled-cluster (DLPNO-CCSD(T)) calculations rationalize the catalyst control and stereochemical outcome.

Electrophilic Phosphonium Cations as Lewis Acid Catalysts in Diels–Alder Reactions and Nazarov Cyclizations

The highly electrophilic fluorophosphonium cation [(C6F5)3PF]+[B(C6F5)4]− is shown to catalyze Diels–Alder reactions of challenging dienophile/enophile combinations and Nazarov cyclizations of various precursors. Several other electrophilic phosphonium cations (EPCs) have been tested for comparison. This systematic study demonstrates the power of these Lewis acids to act as catalysts for synthetically useful pericyclic reactions.

3,20-Dihydroxy-13α-19-norpregna-1,3,5(10)-trienes. Synthesis, structures, and cytotoxic, estrogenic, and antiestrogenic effects

New 3,20-dihydroxy-13α-19-norpregna-1,3,5(10)-trienes were synthesized. The effects of these compounds on breast cancer cells and ERα activation were investigated. The scaffold of compounds containing the six-membered ring D′ annulated at 16α,17α-positions was constructed via the Lewis acid catalyzed Diels-Alder reaction of butadiene with 3-methoxy-13α-19-norpregna-1,3,5(10),16-tetraen-20-one 5 under a pressure of 600 MPa. The hydrogenation of primary cyclohexene adduct 6 followed by the one-pot reduction–demethylation (DIBAH) gave target epimeric 3,20-dihydroxy steroids 8a and 8b. The Corey-Chaykovsky reaction of the same conjugated ketone 5 gave a 16α,17α-methylene-substituted compound. The reaction of the latter with DIBAH yielded 3,20(R,S)-dihydroxy-16α,17α-methyleno-13α-19-norpregna-1,3,5(10)-triene 10. The hydrogenation of the 16,17-double bond of compound 5 produced a mixture of 17α- and 17β-epimeric ketones, reduction–demethylation of which gave 3,20(S)-dihydroxy-13α,17α-19-norpregna-1,3,5(10)-triene 12a and 3,20(R)-dihydroxy-13α,17β-19-norpregna-1,3,5(10)-triene 12b. All compounds were fully characterized by 1D and 2D NMR, HRMS, and X-ray diffraction. All target compounds showed pronounced cytotoxic effect against MCF-7 breast cancer cells and NCI/ADR-RES doxorubicin-resistant cells at micromolar concentrations. The ERα-mediated luciferase reporter gene assay demonstrated that all compounds, except for compound 10, are ERα inhibitors, while cyclopropane compound 10 proved to be an ERα activator. Docking experiments showed that all compounds are well accommodated to LBD ERα but have some differences in the binding mode.

Janus Face of the Steric Effect in a Lewis Acid Catalyst with Size-Exclusion Design: Steric Repulsion and Steric Attraction in the Catalytic Exo-Selective Diels–Alder Reaction

An exo-selective catalytic Diels–Alder reaction was developed using a Lewis acid catalyst with size-exclusion structural design. Exploiting the steric effect, especially the steric attraction, the Lewis acid catalyst was able to reroute the reaction along a higher-energy pathway. The experimental findings were also supported by theoretical calculations. This catalyst development allows an easy and practical access to highly complex and pharmaceutically relevant compounds.

Carbocation Lewis Acid Catalyzed Diels-Alder Reactions of Anthracene Derivatives.

The carbocation salt [Ph3C][BArF] has been identified as a viable Lewis acid catalyst for the Diels-Alder reactions between anthracene derivatives and unsaturated carbonyl compounds with good selectivity and high efficiency.

Asymmetric Diels-Alder Reaction of α,β-Unsaturated Oxazolidin-2-one Derivatives Catalyzed by a Chiral Fe(III)-Bipyridine Diol Complex.

An asymmetric FeIII-bipyridine diol catalyzed Diels-Alder reaction of α,β-unsaturated oxazolidin-2-ones has been developed. Among various FeII/FeIII salts, Fe(ClO4)3·6H2O was selected as the Lewis acid of choice. The use of a low catalyst loading (2 mol % of Fe(ClO4)3·6H2O and 2.4 mol % of Bolm's ligand) afforded high yields (up to 99%) and high enantiomeric excesses (up to 98%) of endo-cycloadducts for the Diels-Alder reaction between cyclopentadiene and substituted acryloyloxazolidin-2-ones. Other noncyclic dienes led to decreased enantioselectivities. A proposed model supports the observed stereoinduction.

An MM and QM Study of Biomimetic Catalysis of Diels-Alder Reactions Using Cyclodextrins.

We performed a computational investigation of the mechanism by which cyclodextrins (CDs) catalyze Diels-Alder reactions between 9-anthracenemethanol and N-cyclohexylmaleimide. Hydrogen bonds (Hbonds) between N-cyclohexylmaleimide and the hydroxyl groups of cyclodextrins were suggested to play an important role in this catalytic process. However, our free energy calculations and molecular dynamics simulations showed that these Hbonds are not stable, and quantum mechanical calculations suggested that the reaction is not promoted by these Hbonds. The binding of 9-anthracenemethanol and N-cyclohexylmaleimide to cyclodextrins was the key to the catalytic process. Cyclodextrins act as a container to hold the two reactants in the cavity, pre-organize them for the reactions, and thus reduce the entropy penalty to the activation free energy. Dimethyl-β-CD was a better catalyst for this specific reaction than β-CD because of its stronger van der Waals interaction with the pre-organized reactants and its better performance in reducing the activation energy. This computational work sheds light on the mechanism of the catalytic reaction by cyclodextrins and introduces new perspectives of supramolecular catalysis.

The use of optically active O-alkyl ester hydrochlorides of L-phenylalanine and L-tyrosine as chiral micellar media for the catalysis of diels-alder reactions

The effect of a range of O -alkyl ester hydrochloride surfactants derived from L-phenylalanine and L-tyrosine as catalysts on the Diels-Alder reaction between cyclopentadiene and methyl acrylate was studied. Both chain lengths (C 8 -C 14 ) and head groups of the surfactants were found to influence the yield and selectivity of the Diels-Alder product. The C 10 derivatives of both phenylalanine and tyrosine surfactants gave the highest yields and selectivity. Phenylalanine ester hydrochlorides showed better catalytic activity than the tyrosine derivatives. Adduct optimum yield was obtained at a concentration relating to their critical micelle concentration (CMC) values. The Diels-Alder reaction was also found to be favored in acidic condition (pH 3) as well as in the presence of lithium chloride (LiCl) as salting out agent. KEY WORDS : Diels-Alder, Chiral catalysts, Phenylalanine, Tyrosine, Micelle, CMC Bull. Chem. Soc. Ethiop. 2017 , 31(3), 509-518. DOI: http://dx.doi.org/10.4314/bcse.v31i3.15

32 3-ヒドロキシ-2-ピロンの塩基触媒Diels-Alder反応の開発と生理活性物質合成への応用(口頭発表の部)

32 3-ヒドロキシ-2-ピロンの塩基触媒Diels-Alder反応の開発と生理活性物質合成への応用(口頭発表の部)

Highly diastereo- and enantioselective synthesis of spirooxindole-cyclohexaneamides through N,N'-dioxide/Ni(ii)-catalyzed Diels-Alder reactions.

Highly efficient asymmetric Diels-Alder reactions of methyleneindolinones with 1,3-dienylcarbamates and 1,2-dihydropyridines have been accomplished by using a chiral N,N'-dioxide/nickel(ii) complex as an efficient catalyst. New kinds of spirooxindole-cyclohexaneamides were achieved in up to 99% yield, >95 : 5 dr, and 99% ee.

Simple primary β-amino alcohol catalyzed enantioselective Diels-Alder reaction of 3-hydroxy-2-pyridones

The simple primary β-amino alcohol catalyzed Diels-Alder reaction of 3-hydroxy-2-pyridones as dienes with N-substituted maleimides to provide the highly substituted optically active isoquinuclidines as a single diastereomers in excellent enantioselectivities (up to 98%) with excellent chemical yields (up to 95%) was demonstrated. A range of simple β-amino alcohols were synthesized from the corresponding inexpensive amino acids and their catalytic activity was examined for this reaction.

New diaryl-substituted azabicyclo[3.2.2]nonanes and their antiprotozoal potencies

Several new diaryl-substituted azabicyclo[3.2.2]nonanes with varying substitution patterns of the aromatic rings and differing amino substitution at a bridgehead atom of the bicyclic ring system were synthesized from bicyclo[2.2.2]octan-2-ones via Schmidt or Beckmann reactions and subsequent reduction. The bicyclic octanones were prepared in a one-pot synthesis from acyclic starting materials or in one step from properly functionalized diarylcyclohexanones which were accessible by a catalyzed Diels–Alder reaction. The characterization of the new compounds was done by UV/Vis spectroscopy, FT-IR spectroscopy, and HRMS. Structural elucidation of isomers was done by NMR spectroscopy using 1D and 2D techniques as well as NOE measurements. The antiprotozoal activities against Plasmodium falciparum K 1 , resistant to chloroquine and pyrimethamine, and against Trypanosoma brucei rhodesiense as well as the cytotoxicities of the new compounds were determined and compared to those of reported compounds. Structure–activity relationships are discussed.

In silico study to evaluate the governing criteria in the BF3 catalyzed Diels-Alder reaction

In silico studies were done on the BF3-catalyzed and uncatalyzed Diels-Alder reactions. The presence of the BF3 is easing the reaction and the effect of the BF3 is related to its position. The simple HOMO-LUMO energy gap was not able to explain the reactions. Instead, the partial ESP charges for the reactants and especially for the TS structures are better criteria to explain the mentioned reactions. More negative charges on the interacting atoms in the transition state structures lead to higher activation energy demand and lower bond orders in the transition state structures. In some cases the steric effect because of the presence of the Me functional group should be considered, as well.

ZrCl4 Catalysed Diastereoselective Synthesis of Spirocarbocyclic Oxindoles via [4+2] Cycloaddition

AbstractSpirocarbocyclic‐oxindole is priviledged scaffold in heterocyclic chemistry, which paved the attention of synthetic chemist due to generation of a new stereocenter. Numerous methodologies have been developed for spirooxindoles but very few methods are available for carbocyclic oxindoles. Most of the reported cycloaddition reactions are five membered rings instead of six membered rings, tethered with oxindole scaffold. Lewis acid catalysed Diels Alder reaction is a comparatively better approach to functionalize this unique scaffold. An efficient diastereoselective synthesis of spirocarbocyclic‐oxindoles with six membered cabocyclic backbone was achieved via ZrCl4 catalyzed [4+2] cycloaddition of α‐ylideneoxindoles with dienes in good to excellent yields within a short span of time.

Correction to Enantioselective Catalytic Diels–Alder Reactions with Enones As Dienophiles

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Enantioselective Catalytic Diels–Alder Reactions with Enones As DienophilesDaniel Carmona*, Fernando Viguri*, Ainara Asenjo, Fernando J. Lahoz, Pilar Garcı́a-Orduña, and Luis A. OroCite this: Organometallics 2016, 35, 9, 1339Publication Date (Web):April 27, 2016Publication History Published online27 April 2016Published inissue 9 May 2016https://doi.org/10.1021/acs.organomet.6b00319Copyright © 2016 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views512Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (102 KB) Get e-Alerts Get e-Alerts

Urea-Functionalized Self-Assembled Molecular Prism for Heterogeneous Catalysis in Water.

Reaction of a ditopic urea "strut" (L1) with cis-(tmen)Pd(NO3)2 yielded a [3+3] self-assembled molecular triangle (T) [L1 = 1,4-di(4-pyridylureido)benzene; tmen = N,N,N',N'-tetramethylethane-1,2-diamine]. Replacing cis-(tmen)Pd(NO3)2 in the above reaction with an equimolar mixture of Pd(NO3)2 and a clip-type donor (L2) yielded a template-free multicomponent 3D trigonal prism (P) decorated with multiple urea moieties [L2 = 3,3'-(1H-1,2,4-triazole-3,5-diyl)dipyridine]. This prism (P) was characterized by NMR spectroscopy, and the structure was confirmed by X-ray crystallography. The P was employed as an effective hydrogen-bond-donor catalyst for Michael reactions of a series of water-insoluble nitro-olefins in an aqueous medium. The P showed better catalytic activity compared to the urea-based ligand L1 and the triangle T. Moreover, the confined nanospace of P in addition to large product outlet windows makes this 3D architecture a perfect molecular vessel to catalyze Diels-Alder reactions of 9-hydroxymethylanthracene with N-substituted maleimide in the aqueous medium. The present results demonstrate new observations on catalytic aqueous Diels-Alder and Michael reactions in heterogeneous fashion employing a discrete 3D architecture of Pd(II). The prism was recycled by simple filtration and reused several times without significant loss of activity.

Turning Cucurbit[8]uril into a Supramolecular Nanoreactor for Asymmetric Catalysis.

Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels–Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid–Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.

Turning Cucurbit[8]uril into a Supramolecular Nanoreactor for Asymmetric Catalysis.

Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels–Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid–Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.

Rosin based epoxy coating: Synthesis, identification and characterization

Ketone type derivative of rosin was prepared by dehydrocarboxylation of isomerized abietic acid. Coupling of dipimaryl ketone with maleic anhydride was performed by acetic acid catalyzed Diels–Alder reaction. Afterwards, the dipimaryl ketone was epoxidized to get the corresponding tetra glycidyl ester. The chemical structure of the synthesized products was confirmed by UV, FTIR and 1H NMR spectroscopic analyses. Cured resins using a rosin-based crosslinker and p-phenylene diamine (a commercial crosslinker) were evaluated using dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and some preliminary universal coating tests. Results showed that the fully rosin-based epoxy system gave better performance than commercially bisphenol-A based one. This finding was attributed to a liquid crystal behavior of the rosin-based crosslinker. Mesomorphic transition temperature and liquid crystalline texture of the rosin-based crosslinker were investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC).

Organocatalytic atroposelective formal Diels-Alder desymmetrization of N-arylmaleimides.

The atroposelective desymmetrization of N-arylmaleimides was realized by means of a primary amine catalyzed Diels-Alder reaction of enones. The chiral axis as new element of chirality is generated under the remote control of the catalyst that selectively drives the formal Diels-Alder reaction through an exclusive stereochemical outcome.