Browse
Submit Data
Databases
API
Help

Dataset Information

20 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Origin of rate enhancement and asynchronicity in iminium catalyzed Diels-Alder reactions.

ABSTRACT: The Diels-Alder reactions between cyclopentadiene and various α,β-unsaturated aldehyde, imine, and iminium dienophiles were quantum chemically studied using a combined density functional theory and coupled-cluster theory approach. Simple iminium catalysts accelerate the Diels-Alder reactions by lowering the reaction barrier up to 20 kcal mol^-1 compared to the parent aldehyde and imine reactions. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal that the iminium catalysts enhance the reactivity by reducing the steric (Pauli) repulsion between the diene and dienophile, which originates from both a more asynchronous reaction mode and a more significant polarization of the π-system away from the incoming diene compared to aldehyde and imine analogs. Notably, we establish that the driving force behind the asynchronicity of the herein studied Diels-Alder reactions is the relief of destabilizing steric (Pauli) repulsion and not the orbital interaction between the terminal carbon of the dienophile and the diene, which is the widely accepted rationale.

SUBMITTER: Vermeeren P

PROVIDER: S-EPMC8163289 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Bifunctional Hydrogen Bond Donor-Catalyzed Diels-Alder Reactions: Origin of Stereoselectivity and Rate Enhancement.

Project description:The selectivity and rate enhancement of bifunctional hydrogen bond donor-catalyzed Diels-Alder reactions between cyclopentadiene and acrolein were quantum chemically studied using density functional theory in combination with coupled-cluster theory. (Thio)ureas render the studied Diels-Alder cycloaddition reactions exo selective and induce a significant acceleration of this process by lowering the reaction barrier by up to 7 kcal mol-1 . Our activation strain and Kohn-Sham molecular orbital analyses uncover that these organocatalysts enhance the Diels-Alder reactivity by reducing the Pauli repulsion between the closed-shell filled π-orbitals of the diene and dienophile, by polarizing the π-orbitals away from the reactive center and not by making the orbital interactions between the reactants stronger. In addition, we establish that the unprecedented exo selectivity of the hydrogen bond donor-catalyzed Diels-Alder reactions is directly related to the larger degree of asynchronicity along this reaction pathway, which is manifested in a relief of destabilizing activation strain and Pauli repulsion.

| S-EPMC8049058 | biostudies-literature

Effect of counterion structure on rates and diastereoselectivities in ?,?-unsaturated iminium-ion Diels-Alder reactions.

Project description:The use of cyclic ?,?-unsaturated iminium-ion dienophiles is documented in two highly diastereoselective Diels-Alder (DA) reactions. The dienophilic counterion was found to have a significant effect on reactivity.

| S-EPMC3408793 | biostudies-literature

Lewis Acid-Catalyzed Diels-Alder Reactions: Reactivity Trends across the Periodic Table.

Project description:The catalytic effect of various weakly interacting Lewis acids (LAs) across the periodic table, based on hydrogen (Group 1), pnictogen (Group 15), chalcogen (Group 16), and halogen (Group 17) bonds, on the Diels-Alder cycloaddition reaction between 1,3-butadiene and methyl acrylate was studied quantum chemically by using relativistic density functional theory. Weakly interacting LAs accelerate the Diels-Alder reaction by lowering the reaction barrier up to 3 kcal mol-1 compared to the uncatalyzed reaction. The reaction barriers systematically increase from halogen<hydrogen<chalcogen<pnictogen-bonded LAs, i. e., the latter have the least catalytic effect. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal that these LAs lower the Diels-Alder reaction barrier by increasing the asynchronicity of the reaction to relieve the otherwise destabilizing Pauli repulsion between the closed-shell filled π-orbitals of diene and dienophile. Notably, the reactivity can be further enhanced on going from a Period 3 to a Period 5 LA, as these species amplify the asynchronicity of the Diels-Alder reaction due to a stronger binding to the dienophile. These findings again demonstrate the generality of the Pauli repulsion-lowering catalysis concept.

| S-EPMC8360170 | biostudies-literature

Chiral NHC-catalyzed oxodiene Diels-Alder reactions with alpha-chloroaldehyde bisulfite salts.

Project description:Alpha-chloroaldehyde bisulfite adducts were successfully employed in chiral NHC-catalyzed hetero-Diels-Alder reactions with various oxodienes under biphasic reaction conditions with high levels of enantioselectivity. This new protocol makes possible enantioselective additions from commercially available chloroacetaldehyde sodium bisulfite and demonstrates that this unique class of catalysts readily tolerates aqueous conditions.

| S-EPMC2728680 | biostudies-literature

How Ionization Catalyzes Diels-Alder Reactions.

Project description:The catalytic effect of ionization on the Diels-Alder reaction between 1,3-butadiene and acrylaldehyde has been studied using relativistic density functional theory (DFT). Removal of an electron from the dienophile, acrylaldehyde, significantly accelerates the Diels-Alder reaction and shifts the reaction mechanism from concerted asynchronous for the neutral Diels-Alder reaction to stepwise for the radical-cation Diels-Alder reaction. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal how ionization of the dienophile enhances the Diels-Alder reactivity via two mechanisms: (i) by amplifying the asymmetry in the dienophile's occupied π-orbitals to such an extent that the reaction goes from concerted asynchronous to stepwise and thus with substantially less steric (Pauli) repulsion per reaction step; (ii) by enhancing the stabilizing orbital interactions that result from the ability of the singly occupied molecular orbital of the radical-cation dienophile to engage in an additional three-electron bonding interaction with the highest occupied molecular orbital of the diene.

| S-EPMC9400981 | biostudies-literature

Synthesis of Polycyclic Nitrogen Heterocycles via Cascade Pd-Catalyzed Alkene Carboamination/Diels-Alder Reactions.

Project description:Cascade Pd-catalyzed alkene carboamination/Diels-Alder reactions between bromodienes and amines bearing two pendant alkenes are described. These transformations generate 4 bonds, 3 rings, and 3-5 stereocenters to afford polycyclic nitrogen heterocycles with high diastereoselectivity.

| S-EPMC4480637 | biostudies-literature

Unveiling the Lewis Acid Catalyzed Diels-Alder Reactions Through the Molecular Electron Density Theory.

Project description:The effects of metal-based Lewis acid (LA) catalysts on the reaction rate and regioselectivity in polar Diels-Alder (P-DA) reactions has been analyzed within the molecular electron density theory (MEDT). A clear linear correlation between the reduction of the activation energies and the increase of the polar character of the reactions measured by analysis of the global electron density transfer at the corresponding transition state structures (TS) is found, a behavior easily predictable by analysis of the electrophilicity ω and nucleophilicity N indices of the reagents. The presence of a strong electron-releasing group in the diene changes the mechanism of these P-DA reactions from a two-stage one-step to a two-step one via formation of a zwitterionic intermediate. However, this change in the reaction mechanism does not have any chemical relevance. This MEDT study makes it possible to establish that the more favorable nucleophilic/electrophilic interactions taking place at the TSs of LA catalyzed P-DA reactions are responsible for the high acceleration and complete regioselectivity experimentally observed.

| S-EPMC7321097 | biostudies-literature

Dual Activation of Aromatic Diels-Alder Reactions.

Project description:The unusually fast Diels-Alder reactions of [5]cyclophanes were analyzed by DFT at the BLYP-D3(BJ)/TZ2P level of theory. The computations were guided by an integrated activation-strain and Kohn-Sham molecular orbital analysis. It is revealed why both [5]metacyclophane and [5]paracyclophane exhibit a significant rate enhancement compared to their planar benzene analogue. The activation strain analyses revealed that the enhanced reactivity originates from 1)?predistortion of the aromatic core resulting in a reduced activation strain of the aromatic diene, and/or 2)?enhanced interaction with the dienophile through a distortion-controlled lowering of the HOMO-LUMO gap within the diene. Both of these physical mechanisms and thus the rate of Diels-Alder cycloaddition can be tuned through different modes of geometrical distortion (meta versus para bridging) and by heteroatom substitution in the aromatic ring. Judicious choice of the bridge and heteroatom in the aromatic core enables effective tuning of the aromatic Diels-Alder reactivity to achieve activation barriers as low as 2?kcal?mol-1 , which is an impressive 35?kcal?mol-1 lower than that of benzene.

| S-EPMC6771859 | biostudies-literature

Intramolecular Diels-Alder reactions of cyclopropenone ketals.

Project description:The first intramolecular cycloaddition reactions of cyclopropenone ketals with tethered electron-deficient, electron-rich, and neutral 1-substituted dienes are reported, constituting inverse electron demand, normal, and neutral Diels-Alder reactions, that provide exclusively the exo [4 + 2] cycloaddition products without the intervention of [1 + 2], [3 + 2], or [3 + 4] cycloadducts in reactions whose courses do not depend on the reaction conditions, the diene activating substituent, or the nature of the tethering.

| S-EPMC2912946 | biostudies-literature

How Lewis Acids Catalyze Diels-Alder Reactions.

Project description:The Lewis acid(LA)-catalyzed Diels-Alder reaction between isoprene and methyl acrylate was investigated quantum chemically using a combined density functional theory and coupled-cluster theory approach. Computed activation energies systematically decrease as the strength of the LA increases along the series I2 <SnCl4 <TiCl4 <ZnCl2 <BF3 <AlCl3 . Emerging from our activation strain and Kohn-Sham molecular orbital bonding analysis was an unprecedented finding, namely that the LAs accelerate the Diels-Alder reaction by a diminished Pauli repulsion between the π-electron systems of the diene and dienophile. Our results oppose the widely accepted view that LAs catalyze the Diels-Alder reaction by enhancing the donor-acceptor [HOMOdiene -LUMOdienophile ] interaction and constitute a novel physical mechanism for this indispensable textbook organic reaction.

| S-EPMC7187354 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data