A Hexapentaene‐Extended Quinocumulene Cyclotrimerized to a Tricyclobutabenzene Derivative

Kawase, Takeshi; Minami, Yuichiro; Nishigaki, Naoki; Okano, Satoshi; Kurata, Hiroyuki; Oda, Masaji

doi:10.1002/anie.200461608

Cited by 16 publications

(7 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first example from Kawase et al is outlined in Scheme 20 and forms a novel tricyclobutabenzene derivative from a precursor in which a [5]cumulene links two quinone rings. 176 The authors suggest a mechanism in which the [5] The second trimerization example describes the cyclotrimerization of [5]Ph to a tricyclodecadiene derivative as reported by Kawamura and coworkers (Scheme 21). 177 The authors suggest that the reaction initiates with a solution-state dimerization of [5]Ph to give the symmetrical [4]radialene.…”

Section: Di-and Trimerizationsmentioning

confidence: 96%

“…The first example from Kawase et al is outlined in Scheme 20 and forms a novel tricyclobutabenzene derivative from a precursor in which a [5]cumulene links two quinone rings. 176 The authors suggest a mechanism in which the [5]cumulene is converted to a radical intermediate via oxidation. This intermediate then dimerizes to a cyclobutene-intermediate and subsequent addition of the third [5]cumulene unit gives a dicyclobutene intermediate.…”

Section: Di-and Trimerizationsmentioning

confidence: 99%

See 1 more Smart Citation

Synthesis and properties of long [n]cumulenes (n≥ 5)

2014

View full text Add to dashboard Cite

Molecules composed of a contiguous sequence of double bonds, the [n]cumulenes, share structural similarities to both of their conjugated relatives, the polyenes and polyynes. The synthesis and properties of [n]cumulenes are, however, quite different from those of either polyenes or polyynes. At an infinite length, [n]cumulenes would provide one structural form of the hypothetical sp-hybridized carbon allotrope carbyne, while shorter derivatives offer model compounds to help to predict the properties of carbyne. Finally, derivatization of the π-electron framework of [n]cumulenes provides a number of different synthetic transformations, with cycloaddition reactions being the most common. In this review, both historical and recent synthetic achievements toward long [n]cumulenes (n ≥ 5) are discussed. This is followed by a description of our current understanding of the physical and electronic structure of [n]cumulenes based on UV/vis spectroscopy and X-ray crystallography. Finally, the reactivity of long [n]cumulenes is described.

show abstract

Section: Di-and Trimerizationsmentioning

confidence: 96%

“…The first example from Kawase et al is outlined in Scheme 20 and forms a novel tricyclobutabenzene derivative from a precursor in which a [5]cumulene links two quinone rings. 176 The authors suggest a mechanism in which the [5]cumulene is converted to a radical intermediate via oxidation. This intermediate then dimerizes to a cyclobutene-intermediate and subsequent addition of the third [5]cumulene unit gives a dicyclobutene intermediate.…”

Section: Di-and Trimerizationsmentioning

confidence: 99%

Synthesis and properties of long [n]cumulenes (n≥ 5)

2014

View full text Add to dashboard Cite

show abstract

“…The groups of Kawamura and Kawase have independently reported the thermal trimerization of [5]cumulenes (not shown). , Analogous dimerization attempts with [5] t Bu 2 Ph give inconclusive results (Scheme ), and the identity of the products could not be established by spectroscopic methods . X-ray crystallographic analysis, however, reveals dimerization to give [4]radialene 31a (but evidence for trimerization is not observed).…”

Section: Reactivity Of [N]cumulenesmentioning

confidence: 99%

Odd [n]Cumulenes (n = 3, 5, 7, 9): Synthesis, Characterization, and Reactivity

2017

View full text Add to dashboard Cite

In comparison to the omnipresent two- and three-dimensional allotropes of carbon, namely, graphite and diamond (as well as recent entries graphene, carbon nanotubes, and fullerenes), a detailed understanding of the one-dimensional carbon allotrope carbyne is not well established, and even the existence of carbyne has been a matter of controversy over the past decades. Composed of sp-hybridized carbon, carbyne could potentially exist in two forms, either as a polyyne (alternating single and triple bonds, expected to show a semiconducting behavior) or as a cumulene (all carbon atoms are connected via double bonds, predicted to show metallic behavior). Although a number of publications are available on the hypothetical structure and properties of carbyne, specific knowledge about its physical and spectroscopic characteristics is still unclear. In order to predict the properties of carbyne, the synthesis and study of model compounds, namely, polyynes and cumulenes, has been a promising avenue. The synthesis of polyynes has been extensively explored in the last decades, culminating with the isolation of a polyyne with 22 acetylene units, which allows extrapolation to the properties of carbyne. Extended cumulenes, on the other hand, have remained much less well-known, and specific studies of properties versus molecular length are quite limited. A limiting factor to the study of [n]cumulenes has been their dramatically increased reactivity, especially in comparison to polyynes of comparable length. For example, most known [7]cumulenes can only be handled in solution, while the polyynes of equivalent length (i.e., a triyne with three acetylene units) are quite stable. [9]Cumulenes are the longest derivatives studied to date. In this Account, we describe our efforts to design and synthesize odd [n]cumulenes (i.e., n = 3, 5, 7, 9) that are sufficiently persistent under ambient conditions to allow in depth characterization of physical and spectral properties. This goal has been achieved through modification of the end-capping groups by increasing the steric bulk and thereby shielding the reactive cumulene framework to provide stable [7]- and [9]cumulenes. An alternative route to stabilization is accomplished via encapsulation of the cumulene skeleton in a macrocycle, that is, formation of cumulene rotaxanes. The new sterically encumbered cumulenic products are reasonably stable under normal laboratory conditions, although some readily undergo cycloaddition reactions to give interesting products. We have explored preliminary trends for the reactivity of long [n]cumulenes. Finally, trends in the series of [n]cumulene model compounds are now discernible, including a thorough consideration of bond length alternation (BLA) in long [n]cumulenes using X-ray crystallographic analyses, as well as electronic properties via UV-vis spectroscopy and cyclic voltammetry.

show abstract

“…In addition, tris(3,4‐dimethylenecyclobuteno)benzene ( 5 ) was investigated computationally,[5a], which revealed weaker bond‐length alternation in the central benzene ring than that in 1 , 2 , and 3 , but stronger than in 4 . Compound 5a , the first derivative of 5 , was synthesized by Oda et al Despite its nonplanarity, 5a demonstrates relatively weak bond‐length alternation in the central benzene ring, which is similar to 5 . The bora, imino, and oxo derivatives of 5 were also explored computationally by Stanger and Tkachenko, and none of these exhibited strong cyclohexatriene‐like bond fixation in the central benzene ring …”

Section: Introductionmentioning

confidence: 99%

Tris(3,4‐dimethylenecyclobuteno)benzene Derivatives with Enhanced Carbon–Carbon Bond‐Length Alternation in Annelated Benzene

et al. 2016

View full text Add to dashboard Cite

Computational analyses of the tris(3,4‐dimethylenecyclobuteno)benzene molecule indicate that the absence of the equivalent of a HOMO of an etheno group between the internal carbon atoms of the annelating butadieno groups is mainly responsible for the relatively weak cyclohexatriene‐like fixation in the central benzene ring. To increase the extent of C–C bond‐length alternation in the benzene moiety, two strategies of modification of the annelating groups are proposed to make the presence of the equivalent of a HOMO of an etheno group between the internal carbon atoms of the annelating butadieno groups. The first is to introduce a π‐electron‐donating heteroatom/group to form a five‐membered ring with the annelating butadieno groups (model I). The extent of bond‐length alternation could be tuned by the choice of the heteroatom/group in model I. The second is to coordinate with transition‐metal groups, such as the irontricarbonyl groups, for the annelating butadieno groups (model II). Computational results predict that molecules generated by using these two strategies could form strong cyclohexatriene‐like fixation of the double bonds in the central benzene ring.

show abstract

A Hexapentaene‐Extended Quinocumulene Cyclotrimerized to a Tricyclobutabenzene Derivative

Cited by 16 publications

References 18 publications

Synthesis and properties of long [n]cumulenes (n≥ 5)

Synthesis and properties of long [n]cumulenes (n≥ 5)

Odd [n]Cumulenes (n = 3, 5, 7, 9): Synthesis, Characterization, and Reactivity

Tris(3,4‐dimethylenecyclobuteno)benzene Derivatives with Enhanced Carbon–Carbon Bond‐Length Alternation in Annelated Benzene

Contact Info

Product

Resources

About