Synthesis of π‐Conjugated Benzocyclotrimers

Guo, Changding; Xia, Debin; Yang, Yulin; Zuo, Xia

doi:10.1002/tcr.201800160

Cited by 5 publications

(6 citation statements)

References 72 publications

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“…The most applied synthetic strategy towards these soluble starphenes is a palladium-catalysed [2+2+2] cycloaddition reaction of in situ generated arynes from appropriate arene derivatives. [11][12][13] Another often used approach is a nickel-mediated Yamamoto coupling reaction of ortho-dibrominated arenes. [2,6,10,14] As an alternative, on-surface synthesis (OSS) in ultra-high vacuum (UHV) allows the preparation, although in minute amounts, of organic structures that are hardly attainable by traditional in-solution chemistry.…”

Section: Introductionmentioning

confidence: 99%

A Large Starphene Comprising Pentacene Branches

et al. 2021

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Starphenes are attractive compounds due to their characteristic physicochemical properties that are inherited from acenes,m aking them interesting compounds for organic electronics and optics.H owever,t he instability and low solubility of larger starphene homologs make their synthesis extremely challenging.H erein, we present an ew strategy leading to pristine [16]starphene in preparative scale.O ur approach is based on as ynthesis of ac arbonyl-protected starphene precursor that is thermally converted in asolid-state form to the neat [16]starphene,which is then characterised with av ariety of analytical methods,s uch as 13 CC P-MAS NMR, TGA, MS MALDI, UV/Vis and FTIR spectroscopy. Furthermore,h igh-resolution STM experiments unambiguously confirm its expected structure and reveal am oderate electronic delocalisation between the pentacene arms.Nucleus-independent chemical shifts NICS(1) are also calculated to survey its aromatic character.

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Section: Introductionmentioning

confidence: 99%

A Large Starphene Comprising Pentacene Branches

et al. 2021

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“…Two features make this transformation particularly interesting for the preparation of large PAHs and nanographenes: (1) the ready availability of ortho -(trimethylsilyl)aryl triflates to be used as precursors of substituted or polycyclic arynes and (2) the significant increase in the molecular complexity in one single step, that is, the easy preparation of structures formed by 3 n + 1 cycles starting from molecules with n cycles. Herein we have selected some examples of Pd-catalyzed aryne cyclotrimerizations to illustrate the potential of this methodology for the preparation of trigonal PAHs and nanographenes. , …”

Section: Introductionmentioning

confidence: 99%

“…Herein we have selected some examples of Pd-catalyzed aryne cyclotrimerizations to illustrate the potential of this methodology for the preparation of trigonal PAHs and nanographenes. 11,12 ■ SYNTHESIS OF SUBSTITUTED TRIPHENYLENES Soon after the discovery of the Pd-catalyzed aryne cyclotrimerization, it was found that a large variety of transition metal complexes are capable of promoting this transformation. For example, it was reported that Ni(0), 9 Cu(I), 13 and Au(I) 14 complexes can efficiently promote the cyclotrimerization of benzyne.…”

Section: ■ Introductionmentioning

confidence: 99%

Synthesis of Nanographenes, Starphenes, and Sterically Congested Polyarenes by Aryne Cyclotrimerization

et al. 2019

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In recent years, synthetic transformations based on aryne chemistry have become particularly popular, mostly due to the spread of methods to generate these highly reactive intermediates in a controlled manner under mild reaction conditions. In fact, aryne cycloadditions such as the Diels− Alder reaction are nowadays widely used for the efficient preparation of polycyclic aromatic compounds. In 1998, our group discovered that arynes can undergo transition metalcatalyzed reactions, a finding that opened new perspectives in aryne chemistry. In particular, Pd-catalyzed [2 + 2 + 2] cycloaddition of arynes allowed the straightforward synthesis of triphenylene derivatives such as starphenes or cloverphenes. We found that this reaction is compatible with different substituents and sterically demanding arynes as starting materials. This transformation is especially useful to increase the molecular complexity in one single step, transforming molecules formed by n cycles in structures with 3n + 1 cycles. In fact, we took advantage of this protocol to prepare a large variety of sterically congested polycyclic aromatic hydrocarbons such as helicenes or twisted polyarenes. Soon after the discovery of the reaction, the co-cyclotrimerization of arynes with other reaction partners, such as electron deficient alkynes, significantly expanded the potential of this transformation. Also the use of catalysts based on alternative metals besides Pd (e.g., Ni, Cu, Au) or the use of other strained intermediates such as cycloalkynes or cycloallenes added value to this reaction. In addition, we realized that the Pd-catalyzed aryne cyclotrimerization reaction is particularly useful for the bottom-up preparation of well-defined nanographenes by chemical methods. Although the extreme insolubility of these planar nanographenes hampered their manipulation and characterization by conventional methods, recent advances in single molecule on-surface characterization by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) with functionalized tips under ultrahigh vacuum (UHV) conditions, permitted the impressive visualization of these nanographenes with submolecular resolution, together with the examination of the corresponding molecular orbital densities. Moreover, arynes have been shown to possess a rich on-surface chemistry. In particular, arynes have been generated and studied on-surface, showing that the reactivity is preserved even at cryogenic temperatures. On-surface aryne cyclotrimerization was also demonstrated to obtain large starphene derivatives. Therefore, it is expected that the combination of aryne cycloadditions and on-surface synthesis will provide notable findings in the near future, including the "àla carte" preparation of graphene materials or the synthesis of elusive molecules with unique properties.

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“…Recently,B unz et al have prepared [13]-and [16]starphene derivatives with bulky triisopropylsilyl-ethynyl groups, [10] which are the longest substituted starphenes prepared to date.H owever,t hese bulky substituents can modify the electronic properties of the molecules,t heir packing and moreover affect interactions with metal surfaces,w hich can be limiting factors in the applications of the substituted starphenes in organic and single-molecule electronics.T he most applied synthetic strategy towards these soluble starphenes is ap alladiumcatalysed [2+ +2+ +2] cycloaddition reaction of in situ generated arynes from appropriate arene derivatives. [11][12][13] Another often used approach is anickel-mediated Yamamoto coupling reaction of ortho-dibrominated arenes. [2,6,10,14] As an alternative,on-surface synthesis (OSS) in ultra-high vacuum (UHV) allows the preparation, although in minute amounts,o fo rganic structures that are hardly attainable by traditional in-solution chemistry.…”

Section: Introductionmentioning

confidence: 99%