Unusual reactivity of highly strained cyclophanes

Bickelhaupt, F.; Wolf, W. H. De

doi:10.1002/(sici)1099-1395(199805)11:5<362::aid-poc34>3.0.co;2-f

Cited by 27 publications

(8 citation statements)

References 35 publications

(61 reference statements)

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“…Thus it would seem that differences in bond lengths exert a more pronounced effect on the degree of bend in the pyrene moiety. This being the case, the judicious incorporation of heteroatoms in the tethers of [ n ](2,7)pyrenophanes should provide a means for fine-tuning the bend of the pyrene unit, much like Bickelhaupt has done for the fine-tuning of the [5]metacyclophane system …”

Section: Resultsmentioning

confidence: 99%

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

et al. 2000

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A new strategy for the synthesis of Buckybowls is presented and initial attempts to implement it are reported. This involves annulation of further rings onto polycyclic aromatic systems that prefer to be planar but have been "pre-bent" by the installation of a tether. Pyrenophane 2b reacts with TCNE and PTAD to give 1:1 and 1:2 adducts, respectively. The less strained pyrenophane 2c is unreactive toward TCNE but gives a 1:2 adduct with PTAD. Attempted electrophilic aromatic brominations of pyrenophane 2e under a variety of conditions were unsuccessful, as were attempts to brominate cyclophanediene 1c, the direct synthetic precursor of 2c. Tether cleavage and addition reactions occurred rather than substitution. In an effort to circumvent tether cleavage problems, [7]-, [8]- and [9](2,7)pyrenophanes 22b-d were prepared. However, attempted bromination and Friedel-Crafts acylations failed. Evidence for the fleeting existence of [6](2,7)pyrenophane 22a was also obtained. Comparison of structural data (X-ray and AM1 calculations) for the pyrenophanes 22a-d with their 1,n-dioxa analogues 2a-d indicates that the nature of the tether has a strong effect on the degree of bend in the pyrene moiety and this led to the identification of trioxapyrenophane 28 as the next target in the quest for increasingly bent pyrenes.

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Section: Resultsmentioning

confidence: 99%

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

et al. 2000

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“…by bending the aromatic ring as in small cyclophanes. 16 Recently, we reported the synthesis of the transition metal complexed 7-phosphanorbornadiene 6 by the unprecedented 1,4-addition of PhPW(CO) 5 (2a) to the highly bent [5]metacyclophane (5) (Scheme 4). 17 The extraordinary thermal stability of 6 was explained by the unfavorable thermodynamics for the retro reaction as the strain in 5 is much higher than that in 6.…”

Section: Resultsmentioning

confidence: 99%

The First Free 7λ³-Phosphanorbornadiene

Eis¹,

Zappey

Kanter³

et al. 2000

J. Am. Chem. Soc.

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The first uncoordinated 7λ 3 -phosphanorbornadiene 10 is reported. This missing member of the class of 7-heteranorbornadienes was prepared by decomplexation of its pentacarbonyltungsten complex 6 with iodine and N-methylimidazole. It is moderately stable at room temperature toward loss of the phosphinidene bridge (PhP:) because the aromatic fragment, [5]metacyclophane ( 5), is a highly strained compound. For this reason, 10 may be considered to be a hyperstable compound. An analysis of the energetics of the system by density functional calculations supports this rationalization.

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“…Although the diyne moiety is not deformed (bond angles 177−179°) the acetylene carbons (C(12), C(13), C(24), and C(25)) are moderately distorted from linearity (165−172°). The tert -butyl-substituted benzene ring is not much distorted (α = 2.3° (for plane C(14)−C(22)−C(23)) and 0.6° (for plane C(15)−C(16)−C(21)), β = 4.6° (for bond C(13)−C(14)) and 4.9° (for bond C(22)−C(24))) . The distance between H(9) and the transannular sp carbons (C(3) and C(4)) is relatively short (2.76 and 2.74 Å, respectively).…”

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confidence: 99%

Facile Intramolecular Cyclization in Oxidative Coupling of Acetylenes Linked to 1,3-Positions of Benzene: Strained [12]Metacyclophanedienetetrayne System

et al. 2003

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Oxidative coupling of ethynylpropellane linked to 1,3,5-position of a benzene core 3b did not give the cage dimer 2 but the dimer 4 having a strained [12]metacyclophanedienetetrayne system. The spectral and structural features of the novel ring system were revealed for the simple dibenzo derivative 6, which was also prepared efficiently by the intramolecular cyclization of the open-chain precursor.

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Unusual reactivity of highly strained cyclophanes

Cited by 27 publications

References 35 publications

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

The First Free 7λ³-Phosphanorbornadiene

Facile Intramolecular Cyclization in Oxidative Coupling of Acetylenes Linked to 1,3-Positions of Benzene: Strained [12]Metacyclophanedienetetrayne System

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Unusual reactivity of highly strained cyclophanes

Cited by 27 publications

References 35 publications

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

Nonplanar Aromatic Compounds. 3. A Proposed New Strategy for the Synthesis of Buckybowls. Synthesis, Structure and Reactions of [7]-, [8]- and [9](2,7)Pyrenophanes

The First Free 7λ3-Phosphanorbornadiene

Facile Intramolecular Cyclization in Oxidative Coupling of Acetylenes Linked to 1,3-Positions of Benzene: Strained [12]Metacyclophanedienetetrayne System

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The First Free 7λ³-Phosphanorbornadiene