Towards Nonalternant Nanographenes through Self‐Promoted Intramolecular Indenoannulation Cascade by C−F Bond Activation

Abstract

What new scientific questions does this work raise?Every chemist knows that aluminum oxide is quite inert from a chemical viewpoint. Meanwhile, the aromatic CÀFb ond is one of the strongest and thus unreactive bonds in organic chemistry.N evertheless, when mixed together these two allegedly indifferent components become extremely reactive. In our work, we use aluminum oxide to trigger the activation of the CÀFb ond, which in the light of the evidence transforms into an extremely useful functionality.A sw ith Al 2 O 3 ,d espite numerous studies on its structure and properties, activated alumina still remains a" black box". In reality,t he shape of catalytic centers, the role of water,a nd ap lethora of other details are still to be investigated. We hope that our study will attract the attention of other groups to the issue. Since alumina is capable of such an unexpected and potentially useful transformation, we believe it is worth trying to understand the reaction in order to adjust and direct the process.

2,7,11,16‐Tetra‐tert‐Butyl Tetraindenopyrene Revisited by an “Inverse” Synthetic Approach

“…[12,13] However, only the bowl-to-bowl inversion barrier calculated by DFT (B3LYP/6-31G*) was discussed, and no further details,s uch as geometrical parameters or energy levels of frontierm olecular orbitals, were provided (see also the Discussion below). [14] To obtain further insights into the structural details of TIP 2,d ispersion-corrected (D3) [27] DFT methods (B3LYP/6-311G(d,p)) were used to calculate molecular properties. It wasf ound that the input geometry (MM2 optimized models) is crucial to the outcomeo ft he DFT optimization.…”

“…the synthesis of as tructurally relatedt etra-n-octyl TIP by an alumina-mediated HF elimination was reported. [14] Unfortunately,n either full characterization nor detailed discussion on photophysical or electrochemical properties were included. It is known that the Kr egion of pyrene has as ubstantial olefin character,a nd thus the CÀHa ctivation may occur by aH eck coupling mechanism, rather than by aC ÀHa ctivation in which the hydrogen is abstracted from ab enzene ring.…”

Alumina-promoted oxodefluorination

“…Such hydrolysis of C-F bond has already been observed as a side process. 41 Unlike the reported transformation, the current precursor contains two uorine atoms, whereas the polarization of the second C(aryl)-F bond induces the second C-O coupling, this time intramolecular, and subsequent covalent detachment of the product. Some other possible mechanisms occurring via aryne-particles or dehydration were excluded (see ESI †).…”

“…As a part of our ongoing research on alumina mediated C-F activation, 39,40 we have observed an interesting competition between C(aryl)-C(aryl) coupling and formation of oxygencontaining side products. 41 In certain cases (i.e. when two uorine atoms are dislocated in bay-region) the side products turned out to contain dibenzofuran's moiety.…”

“…43,44 As any other heterogeneous process, this reaction is quite likely to have a complicated manner. However, some pieces of evidence on C(aryl)-F polarization 41,45,46 allow us to suggest the key steps of the transformation. Alumina induces a partial positive charge on carbon generating incipient phenyl cation species, 47 which are to interact with proximal moieties.…”