Origin of the “endo rule” in Diels-Alder reactions

Fernández, Israel; Bickelhaupt, F. Matthias

doi:10.1002/jcc.23500

Cited by 83 publications

(61 citation statements)

References 67 publications

(33 reference statements)

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“…11 However, the importance of these interactions has been questioned in recent years. 12 A distortion-interaction model has been used to explain the endo preference of the intermolecular cycloaddition between cyclic dienes and cycloalkenones. 4 Furthermore, the steric clash between the C sp3 -H of the cycloalkenone and the hydrogen of the internal double bond destabilizes the exo transition state, as shown for cyclobutenone 1 in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Intramolecular Diels–Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects

et al. 2014

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The intramolecular Diels–Alder reactions of cycloalkenones and terminal dienes occur with high endo stereoselectivity, both thermally and under Lewis-acidic conditions. Through computations, we show that steric repulsion and tether conformation govern the selectivity of the reaction, and incorporation of either BF3 or α-halogenation increases the rate of cycloaddition. With a longer tether, isomerization from a terminal diene to the more stable internal diene results in a more facile cycloaddition.

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Section: Resultsmentioning

confidence: 99%

Intramolecular Diels–Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects

et al. 2014

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“…Finally, we recently reported that strain, instead of second orbital interactions, is also the major factor behind the well-known endo-rule, empirically formulated by Alder and Stein. 38 3.2.3. Double group transfer reactions.…”

Section: Pericyclic Reactionsmentioning

confidence: 98%

The activation strain model and molecular orbital theory: understanding and designing chemical reactions

2014

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In this Tutorial Review, we make the point that a true understanding of trends in reactivity (as opposed to measuring or simply computing them) requires a causal reactivity model. To this end, we present and discuss the Activation Strain Model (ASM). The ASM establishes the desired causal relationship between reaction barriers, on one hand, and the properties of reactants and characteristics of reaction mechanisms, on the other hand. In the ASM, the potential energy surface ΔE(ζ) along the reaction coordinate ζ is decomposed into the strain ΔEstrain(ζ) of the reactants that become increasingly deformed as the reaction proceeds, plus the interaction ΔEint(ζ) between these deformed reactants, i.e., ΔE(ζ) = ΔEstrain(ζ) + ΔEint(ζ). The ASM can be used in conjunction with any quantum chemical program. An analysis of the method and its application to problems in organic and organometallic chemistry illustrate the power of the ASM as a unifying concept and a tool for rational design of reactants and catalysts.

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“…However, there tends to be a preference for the endo product in many of these reactions (the so‐called ′ endo rule′). The origin of this effect has been the subject of much debate and factors such as secondary orbital interactions and unfavourable steric interactions between oxygen atoms on the dienophile and the methylene protons on cyclopentadiene in the exo transition state are likely to play a role . A number of studies have explored DA reactions involving cyclopentadiene in ILs .…”

Section: Resultsmentioning

confidence: 99%

Liquid‐Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction

Bruce

Gao

Lopes

et al. 2016

Chemistry A European J

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Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic.

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Origin of the “endo rule” in Diels-Alder reactions

Cited by 83 publications

References 67 publications

Intramolecular Diels–Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects

Intramolecular Diels–Alder Reactions of Cycloalkenones: Stereoselectivity, Lewis Acid Acceleration, and Halogen Substituent Effects

The activation strain model and molecular orbital theory: understanding and designing chemical reactions

Liquid‐Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction

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