Relative configurations of the chiral 2,7- and 3,7-dimethyl-7-(methoxymethyl)cyclohepta-1,3,5-trienes

Baldwin, John E.; Broline, Bruce M.

doi:10.1021/jo00347a001

Cited by 16 publications

(4 citation statements)

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“…It is also worth commenting that this twirling migration of the NiP 2 fragment corresponds to the “retention” motion predicted for the orbitally allowed degenerate sigmatropic shifts in norcaradiene . Ironically, however, norcaradiene rearrangements have been shown experimentally and theoreticallyto proceed via the orbitally forbidden “inversion” pathway. We have also calculated a transition state for migration around the benzonitrile arene ring via an inversion pathway (which corresponds to a geometry with the η 3 -arene parallel to the NiP 2 plane), and it lies ∼8 kcal/mol higher in energy than the retention pathway (see Supporting Information, Figure SI-4).…”

Section: Resultsmentioning

confidence: 72%

Experimental and Theoretical Examination of C−CN Bond Activation of Benzonitrile Using Zerovalent Nickel

et al. 2008

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The nickel(0) fragment [Ni(dippe)] was reacted with benzonitrile and initially formed both η2-nitrile and η2-arene complexes at −60 °C. When the sample was warmed to room temperature, the latter completely converted to the η2-nitrile product, which is known to give an equilibrium mixture with the Ni(II) oxidative addition product [(dippe)Ni(Ph)(CN)]. Thermodynamic parameters for this equilibrium have been obtained in both polar and nonpolar solvents (THF vs toluene). Use of density functional theory showed three relatively stable η2-arene intermediates, as well as six well-defined transition states located on the potential energy surface between the η2-nitrile complex and the C−CN bond activation product. Among these transition states, those for the migration of the nickel metal between the carbon−carbon bonds of the phenyl ring are at lower energies than those connecting the η2-nitrile complex to the η2-arene intermediate and the η2-arene intermediate to the C−CN bond activation product. Calculations were carried out both in the gas phase and in solution using the PCM model, which was critical for simulation of the different polar solvent environments in these experiments.

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Section: Resultsmentioning

confidence: 72%

Experimental and Theoretical Examination of C−CN Bond Activation of Benzonitrile Using Zerovalent Nickel

et al. 2008

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“…The [1,5]-sigmatropic shift of norcaradiene is an example of a “walk rearrangement”, in which a substituted methylene “walks” around the perimeter of an aromatic ring. It came as a major surprise when Klärner reported a series of elegant studies establishing that this reaction occurs mostly with inversion of configuration at the migrating carbon atom .…”

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confidence: 99%

“…Several examples are summarized in Figure . Compounds bearing substituents on the cyclopropane ring (C-7) of the norcaradiene exhibit inversion with stereoselectivities of 92 to ≥99% …”

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confidence: 99%

Origin of the Preference for the Orbital Symmetry Forbidden Stereochemistry of the 1,5-Sigmatropic Shift of Substituted Norcaradienes

et al. 1999

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“…After reduction with lithium aluminum hydride (LAH), the resultant diol was converted into bis-carbonate 3 . A three-step sequence of ring expansion, including formation and cleavage of a cyclopropane ring, afforded cycloheptenone 5 , and subsequent hydrogenation furnished cycloheptanone 6 . Upon treatment with sodium hydride in the presence of a catalytic amount of ethanol, 6 underwent Dieckmann condensation to form a lactone .…”

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confidence: 99%

Construction of the [7–5–5] Tricyclic Core of Daphniphyllum Alkaloids via a Cationic Cascade Reaction

Nakajima

Yokoshima

2022

Org. Lett.

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tricyclic core of daphniphyllum alkaloids, containing contiguous stereogenic centers at C14 and C15 and a tetrasubstituted alkene moiety between C9 and C10, was constructed via a cascade reaction that involved an electrocyclic reaction of a pentadienyl cation and intramolecular interception of the resultant cyclopentenyl cation. D aphniphyllum alkaloids, isolated from plants of the genus Daphniphyllum, 1 exhibit diverse structures; however, common structural features are also found. Some have a [7− 5−5] tricyclic core bearing contiguous stereogenic centers at C14 and C15 and a tetrasubstituted alkene between C9 and C10 (Figure 1). The molecules with these features, including yuzurimine, yuzurine, paxdaphnine B, and calyciphyllines A and N, comprise the major group of the daphniphyllum alkaloids. From a synthesis viewpoint, 2 however, the methods for constructing the system containing both the contiguous stereogenic centers and the tetrasubstituted alkene are limited. 3 Only two total syntheses, that of calyciphylline N from Shvartsbart and Smith 4 and that of daphniyunnine A from Li and co-workers, 5 have been reported. The scarcity of such syntheses might be attributable to the tetrasubstituted alkene moiety.

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Relative configurations of the chiral 2,7- and 3,7-dimethyl-7-(methoxymethyl)cyclohepta-1,3,5-trienes

Abstract: A chiral sample of 5-(methoxymethyl)-5-methylcyclohept-2-en-l-one was synthesized and converted in two separate reaction sequences to 2,7-and 3,7-dimethyl-7-(methoxymethyl)cycloheptatriene. The synthetic chemistry

Cited by 16 publications

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Experimental and Theoretical Examination of C−CN Bond Activation of Benzonitrile Using Zerovalent Nickel

Experimental and Theoretical Examination of C−CN Bond Activation of Benzonitrile Using Zerovalent Nickel

Origin of the Preference for the Orbital Symmetry Forbidden Stereochemistry of the 1,5-Sigmatropic Shift of Substituted Norcaradienes

Construction of the [7–5–5] Tricyclic Core of Daphniphyllum Alkaloids via a Cationic Cascade Reaction

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