Propellanes. 13. Magnitude of the norcaradiene-cycloheptatriene energy difference

Warner, Philip; Lu, Shih-Lai

doi:10.1021/ja00521a053

Cited by 29 publications

(2 citation statements)

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“…The thermal isomerization may involve a norcaradiene intermediate which opens to the much more stable toluene (Figure ). The energy difference between CHT and norcaradiene in the ground state is estimated to be small, about 4.5 kcal/mol …”

Section: Introductionmentioning

confidence: 97%

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Matrix Photochemistry of Cycloheptatriene: Site Effects

1998

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An experimental study of CHT photolysis at 2537 Å in argon and nitrogen (N2) matrices is presented. The sole IR detectable product is identified as BCHD: bicyclo[3.2.0]hepta-2,6-diene. It is found that CHT molecules trapped in spectroscopically distinct sites were converted to the product at different rates. In the initial stages of the photolysis, the population of some CHT trapping sites increased, indicating site population transfer. In the long run, however, all sites were depleted. Molecular dynamics simulations are performed to estimate the structure of the different sites, and together with a kinetic model, are used to account for the UV induced changes. A tentative energy level diagram of the system is offered, in an attempt to rationalize the total absence of toluene which is formed predominantly in the gas-phase irradiation of CHT at this wavelength. The “twin state” concept is instrumental in this rationalization.

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Section: Introductionmentioning

confidence: 97%

“…The energy difference between CHT and norcaradiene in the ground state is estimated to be small, about 4.5 kcal/mol. 23 Figure 2 shows an energy diagram relevant for CHT photochemistry. The enthalpies of formation of the different species are shown relative to the thermodynamically most stable isomer, toluene.…”

Section: Introductionmentioning

confidence: 99%

Matrix Photochemistry of Cycloheptatriene: Site Effects

1998

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Organocopper Reagents: Substitution, Conjugate Addition, Carbo/Metallocupration, and Other Reactions

1992

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Well over a decade ago, two reviews were contributed to the Organic Reactions series covering substitution and conjugate addition reactions in organocopper chemistry. Their appearance, which highlighted most of the early work in this field, served not only as a source of invaluable references to original literature reports, but also stimulated a vast number of subsequent studies on the properties and uses of organocopper complexes. The work cited in this chapter, which dates from ca. 1975, concerns in large measure uses of organocopper complexes originating from either catalytic or stoichiometric quantities of a copper(I) halide together with a Grignard (RMgX) or organolithium (RLi) reagent. These combinations form either neutral organocopper reagents RCu ( 1 ) or copper(I) monoanionic salts R 2 CuM (M = Li or MgX), commonly referred to as “lower‐order” species. The latter ate complexes with lithium as gegenion ( 2 ) are also known as “Gilman reagents” in recognition of their origins. Copper(I) cyanide is also an excellent precursor, affording homogeneous mixtures of lower order cyanocuprates RCu(CN)Li, ( 3 ), upon treatment with an equivalent of an organolithium. The strength of the CuCN linkage presumably accounts for direct cuprate formation with 1 equivalent of the organolithium, rather than the metathesis that occurs with copper(I) chloride, bromide, or iodide. While use of reagents ( 1 ), ( 2 ) and ( 3 ) alone can be aptly classified as broad‐based and intense, their importance has further encouraged extensive development of variations on these themes (i.e., their composition and reactivity profiles). Reagents ( 1–3 ) have been found to be unexpectedly compatible with certain electrophilic additives at low temperatures, which substantially alter their reactivity. Rather than forming ( 2 ) from 2 equivalents of the same RLi, different organolithiums can be utilized to give R T R R CuLi, ( 4 ), conserving potentially valuable RLi. This scenario raises the question of controlling the selectivity of transfer of the desired ligand R T rather than the anticipated residual (or “dummy”) group R R from copper to electrophilic carbon. Fortunately, many solutions to this problem now exist. Admixture of 2RLi (or R T Li + R R Li) with copper(I) cyanide proceeds beyond the stage of ( 3 ) to ultimately arrive at copper(I) dianionic complexes 5 , the so‐called “higher‐order” cyanocuprates. Undoubtedly it is the cyano ligand, with its π‐acidic nature, which enables copper to accept a third negatively charged ligand. Although reagents ( 5 ) do not yet share in all of the benefits offered by time in comparison with their lower‐order counterparts, they nicely complement prior art. Moreover, as with species ( 1–4 ), they continue to evolve, providing the synthetic community with alternatives for highly selective and efficient means of making key carbon–carbon bonds.

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Walk Rearrangements in [n.1.0] Bicyclic Compounds

Klärner

1984

Topics in Stereochemistry

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Propellanes. 13. Magnitude of the norcaradiene-cycloheptatriene energy difference

Cited by 29 publications

References 4 publications

Matrix Photochemistry of Cycloheptatriene: Site Effects

Matrix Photochemistry of Cycloheptatriene: Site Effects

Organocopper Reagents: Substitution, Conjugate Addition, Carbo/Metallocupration, and Other Reactions

Walk Rearrangements in [n.1.0] Bicyclic Compounds

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