Triangulanes: stereoisomerism and general method of synthesis

Зефиров, Н. С.; Kozhushkov, Sergei I.; Kuznetsova, Т. S.; Kokoreva, O. V.; Lukin, K. A.; Уграк, Б. И.; Tratch, Serge S.

doi:10.1021/ja00177a034

Cited by 59 publications

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“…The general approach to the very complicated synthesis of triangulanes was developed by Zefirov et al (1990). Since then, systematic experimental studies of the structures of triangulanes and of the strained intermediates required for the synthesis have been started (Boese, 1992;Lukin, Kozhushkov, Zefirov, Yufit & Struchkov, 1993;Boese, Haumann, Eluvathingal, Kiran, Kozhushkov & de Meijere, 1996).…”

Section: Introductionmentioning

confidence: 99%

Experimental charge density study of 7-dispiro[2.0.2.1]heptane carboxylic acid

Yufit¹,

Mallinson²,

Muir³

et al. 1996

Acta Crystallogr Sect B

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The experimental charge density distribution in 7-dispiro[2.0.2.1]heptane carboxylic acid has been determined using single-crystal X-ray diffraction data measured at 100 K. Multipole refinement converged at R-0.023 for 5539 reflections with I > 30-(/) and sin 0/A < 1.08 ]k -1 . Inclusion of hexadecapole functions for C atoms in the refinement is shown to be necessary. Experimental maps of the deformation density and of the Laplacian of p are in good agreement with those from ab initio calculations and also have some features specific for polyspirocyclopropanes. Analysis of the bond critical-point properties reveals that the effect of the 7r-acceptor hydroxycarbonyl substituent is more pronounced on the endo-side of the molecule, which can be related to the chemical behaviour of the compound. The influence of small conformational changes on the bond length distribution in the skeleton is also discussed.

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Section: Introductionmentioning

confidence: 99%

Experimental charge density study of 7-dispiro[2.0.2.1]heptane carboxylic acid

Yufit¹,

Mallinson²,

Muir³

et al. 1996

Acta Crystallogr Sect B

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“…The family of spiro-linked cyclopropane aggregates, the so-called [n]triangulanes [4], consists of linear, branched, and cyclic arrays [5]. Among them, the linear triangulanes with more than three spiro-linked cyclopropane units display an interesting stereochemical phenomenon in that they are chiral, but with stereogenic centers that have four different alkyl substituents only [6].…”

Section: The First Enantiometrically Pure [N]triangulanesmentioning

confidence: 99%

“…The absolute configuration of one enantiomer was established as being R by an X-ray crystal structure analysis of its α-phenylethylamide. Esterification, cyclopropanation, diastereomer separation at the stage of the [3]triangulanecarboxylate, reduction, conversion to the bromide, dehydrobromination, and cyclopropanation led to enantiomerically pure [4]triangulane (ee, ≥98 % according to gas chromatography on a chiral phase column) (Scheme 1). The most striking feature of this hydrocarbon, which has no chromophore and is transparent in the UV region down to 200 nm, is its specific rotation of 192.7°at 589 nm.…”

Section: The First Enantiometrically Pure [N]triangulanesmentioning

confidence: 99%

“…Scheme 1 First synthesis of enantiomerically pure (M)-(-)- [4]triangulane and a comparison of its measured and DFT/SCI-computed specific rotations [7]. (a) BF 3 ؒEt 2 O, EtOH, 78 °C, 2 h; (b) CH 2 I 2 , Zn, DME, ultrasound, 80°C, 2 h; (c) LiAlH 4 A line connecting the methylene groups of the inner spiropentane moieties with one each of the outer rings resembles a mechanical model of the helicity of [4]-, [5]-, and [6]triangulane. The lowest unoccupied molecular orbitals express the same feature.…”

Section: The First Enantiometrically Pure [N]triangulanesmentioning

confidence: 99%

“…Fortunately, three of the four diastereomeric ethyl [4]triangulanecarboxylates obtained by rhodium-catalyzed cyclopropanation with ethyl diazoacetate of either one of the enantiomerically pure 1-methylene [3]triangulanes could be distilled off the remaining one through a high-performance concentric tube column, and the residue in the distillation flask proved-by X-ray crystallography-to be one of two diastereomers that could be used to proceed further (Scheme 2) [8].…”

Section: The First Enantiometrically Pure [N]triangulanesmentioning

confidence: 99%

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New Structurally Interesting Cyclopropane Derivatives: A World of Wonders and Surprises

et al. 2003

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The structurally intriguing [4]-and [5]triangulanes have been prepared in enantiomerically pure form. Their surprisingly high specific rotations are well reproduced by DFT/SCI computations and stem from the fact that these hydrocarbons essentially are σ-helicenes (i.e., rigidly held helical arrangements of σ-bonds). Some light is shed on the properties of radical cations derived from [3]-and [4]rotanes. While the former adopts C s or C 2v symmetry, the latter retains the D 4h symmetry of the neutral hydrocarbon, according to highlevel computations. Experimental and computational evidence is also presented that the antiaromatic cyclopentadienyl cation is stabilized as a singlet ground state by five cyclopropyl substituents. Yet, the three cyclopropyl groups in tricyclopropylamine do not favor the formation of its radical cation, because they are not in the proper orientation. When this amine radical cation is generated by cobalt γ-irradiation in a Freon matrix, evidence for a significant conformational change is obtained by EPR spectroscopy. Finally, the conformational dynamics of the newly prepared crowded molecules tetracyclopropyl-and tetraisopropylmethane are discussed.

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Das erste enantiomerenreine Triangulan: (M)-Trispiro[2.0.0.2.1.1]nonan ist ein σ-[4]Helicen

Meijere¹,

Хлебников²,

Kostikov³

et al. 1999

Angewandte Chemie

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Professor Hans-Jürgen Quadbeck-Seeger zum 60. Geburtstag gewidmet Enantiomerenreine chirale Verbindungen, die im üblicherweise genutzten UV/Vis-Spektralbereich zwischen 200 und 800 nm nicht optisch aktiv sind, sind als kryptochiral bezeichnet worden. [1] Wie von Wynberg et al. vor fast 35 Jahren belegt wurde, [2] zeigen chirale Kohlenwasserstoffe mit vier verschiedenen Alkylgruppen an ihren Chiralitätszentren selbst in reiner Form keine optische Drehung und sind demnach kryptochiral. Dies geht wahrscheinlich auf die konformative Beweglichkeit der Alkylketten in solchen acyclischen Kohlenwasserstoffen zurück. Im Unterschied dazu sind [n]Triangulane 1, [3] d. h. Kohlenwasserstoffe, die ausschlieûlich aus spiroanellierten und dadurch abwechselnd senkrecht zueinander stehenden Cyclopropanringen bestehen, vollkommen starr. Viele der höheren [n]Triangulane (n ! 4), die keine Chiralitätszentren enthalten, sind symmetriebedingt chiral, [4] und sie sollten sich nicht kryptochiral verhalten, obwohl sie gesättigte Kohlenwasserstoffe sind. Um diese Hypothese zu testen, haben wir eine Synthese des enantiomerenreinen (M)-[4]Triangulans (M)-2, des kleinsten chiralen [n]Triangulans, entwickelt. [4] Racemisches [4]Triangulan rac-2 wurde erstmals 1973 synthetisiert, [5] und in der Zwischenzeit wurden verbesserte Synthesen [6] sowie spek-ZUSCHRIFTEN

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Triangulanes: stereoisomerism and general method of synthesis

Cited by 59 publications

References 0 publications

Experimental charge density study of 7-dispiro[2.0.2.1]heptane carboxylic acid

Experimental charge density study of 7-dispiro[2.0.2.1]heptane carboxylic acid

New Structurally Interesting Cyclopropane Derivatives: A World of Wonders and Surprises

Das erste enantiomerenreine Triangulan: (M)-Trispiro[2.0.0.2.1.1]nonan ist ein σ-[4]Helicen

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