The adduct of tropone and cyclopentadiene: a new type of cyclic reaction

Cookson, R. C.; Drake, B.; Hudec, J.; Morrison, A. B.

doi:10.1039/c19660000015

Cited by 39 publications

(38 citation statements)

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“…This reaction is included into the so-called higher-order cycloadditions, excellent tools for solving synthetic challenges [37,38]. The novel organocatalytic asymmetric higher-order cycloaddition paves the way for further development in this area for the [3.2.1] bicyclic systems.…”

Section: Chiral Organocatalysis For the Synthesis Of Bicyclo[321mentioning

confidence: 99%

Organocatalyzed Synthesis of [3.2.1] Bicyclooctanes

et al. 2018

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Organocatalysis constitutes one of the main research areas in organic chemistry from the last two decades. This chemistry has been applied to the synthesis of many natural products and structures in a manner that reduces the residues and so the ecological impact. In this review, we consider the work that has been done for the synthesis of bicyclo[3.2.1]octane framework. This structure is present in many natural products with very important biological activities.

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Section: Chiral Organocatalysis For the Synthesis Of Bicyclo[321mentioning

confidence: 99%

Organocatalyzed Synthesis of [3.2.1] Bicyclooctanes

et al. 2018

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“…They also predicted that the reaction would give the exo stereochemistry preferentially [2], in contrast to the endo preference known for the Diels±Alder cycloaddition. Shortly thereafter, Cookson et al [3] and Ito and coworkers [4] reported that cyclopentadiene and tropone react at 80°C to give the exo [6 + 4] adduct stereospeci®cally. Houk and Woodward [5,6] reported several [6 + 4] cycloadditions of cyclopentadienones with tropone and cycloheptatriene, in competition with [4 + 2] and [8 + 2] processes (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Transition structures and exo/endo stereoselectivities of concerted [6 + 4] cycloadditions with density functional theory

Goldstein

Beno

Houk

1999

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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Density functional theory transition structures were located for three concerted [6 + 4] cycloaddition reactions involving cis-hexatriene and butadiene, cyclopentadiene and cycloheptatriene, and cyclopentadiene and tropone. Geometries, energies, and entropies were computed at the Becke3LYP/6-31G* level. The activation energy of the concerted [6 + 4] cycloaddition of hexatriene and butadiene is 33.3 kcal/mol, about 8 kcal/mol above the activation energy of the butadiene plus ethylene [4 + 2] cycloaddition. The endo concerted [6 + 4] transition state is 1.1 kcal/mol higher than the exo. The [6 + 4] reaction of cyclopentadiene and cycloheptatriene has a barrier of 25.9 kcal/mol, while the cyclopentadiene± tropone barrier drops to 20.7 kcal/mol.

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“…Because of the complicating [1,5]-sigmatropic rearrangement in cyclopentadiene and the instability of ketenes, these reactions are not readily amenable to a standard study of their intermolecular KIEs. However, the 12 C/ 13 C isotopic composition at C1 versus C4 and C2 versus C3 of the product 4 should reflect an intramolecular isotope effect.…”

Section: Kinetic Isotope Effectsmentioning

confidence: 99%

“…32 The [2 + 2] cycloadditions of ketenes played a significant role in the elaboration of the WoodwardHoffmann rules, 33 and their particularly facile reactions with 1,3-dienes have found substantial synthetic utility. It was therefore quite momentous when Machiguchi and Yamabe reported that [4 + 2] cycloadducts (e.g., 3) are the initial product in reactions of diphenylketene (2) with cyclic dienes such as cyclopentadiene (1). 34 The ultimate cyclobutanones (e.g., 4) were concluded to arise by a [3,3]-sigmatropic (Claisen) rearrangement of the initial product.…”

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confidence: 99%

Dynamic Effects on the Periselectivity, Rate, Isotope Effects, and Mechanism of Cycloadditions of Ketenes with Cyclopentadiene

2006

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The cycloadditions of cyclopentadiene with diphenylketene and dichloroketene are studied by a combination of kinetic and product studies, kinetic isotope effects, standard theoretical calculations, and trajectory calculations. In contrast to recent reports, the reaction of cyclopentadiene with diphenylketene affords both [4 + 2] and [2 + 2] cycloadducts directly. This is surprising, since there is only one low-energy transition structure for adduct formation in mPW1K calculations, but quasiclassical trajectories started from this single transition structure afford both [4 + 2] and [2 + 2] products. The dichloroketene reaction is finely balanced between [4 + 2] and [2 + 2] cycloaddition modes in mPW1K calculations, as the minimum-energy path (MEP) leads to different products depending on the basis set. The MEP is misleading in predicting a single product, as trajectory studies for the dichloroketene reaction predict that both [4 + 2] and [2 + 2] products should be formed. The periselectivity does not reflect transition state orbital interactions. The 13 C isotope effects for the dichloroketene reaction are well-predicted from the mPW1K/6−31+G** transition structure. However, the isotope effects for the diphenylketene reaction are not predictable from the cycloaddition transition structure and transition state theory. The isotope effects also appear inconsistent with kinetic observations, but the trajectory studies evince that non-statistical recrossing can reconcile the apparently contradictory observations. B3LYP calculations predict a shallow intermediate on the energy surface, but trajectory studies suggest that the differing B3LYP and mPW1K surfaces do not result in qualitatively differing mechanisms. Overall, an understanding of the products, rates, selectivities, isotope effects, and mechanism in these reactions requires the explicit consideration of dynamic trajectories.Selectivity in cycloadditions may take many forms, e.g., endo/exo stereoselectivity, regioselectivity, facial stereoselectivity, and diene/dienophile role selectivity. When two distinct formally allowed processes are possible, as in the [4 + 2] versus [6 + 4] cycloadditions of cyclopentadiene with tropone, 1 their differentiation is referred to as periselectivity. The underlying framework within which chemists usually understand any of these forms of selectivity is transition state theory (TST). The preferred product would be that involving the lowest-energy transition state, and the degree of selectivity would be determined by the relative energies for separate transition states. Even when there is no enthalpic barrier, reactivity and selectivity can be discussed in terms of free-energy barriers. 2 Qualitative theories of selectivity such as FMO theory may be thought of as a simplified surrogate for TST, easing the task of predicting which cycloaddition barrier is lowest in energy.singleton@mail.chem.tamu.edu. Publisher's Disclaimer: This PDF receipt will only be used as the basis for generating PubMed Central (PMC) documents. PMC ...

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The adduct of tropone and cyclopentadiene: a new type of cyclic reaction

Cited by 39 publications

References 0 publications

Organocatalyzed Synthesis of [3.2.1] Bicyclooctanes

Organocatalyzed Synthesis of [3.2.1] Bicyclooctanes

Transition structures and exo/endo stereoselectivities of concerted [6 + 4] cycloadditions with density functional theory

Dynamic Effects on the Periselectivity, Rate, Isotope Effects, and Mechanism of Cycloadditions of Ketenes with Cyclopentadiene

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