Novel Fluorophores based on Regioselective Intramolecular Friedel–Crafts Acylation of the Pyrene Ring Using Triflic Acid

Abstract

The extension of the pyrene ring from dimethyl 2,2'-(pyrene-1,6-diyl)dibenzoate derivatives by an intramolecular Friedel-Crafts acylation can be realized in an efficient and regioselective manner using triflic acid as proton source. Naphtho-tetracenone derivatives are obtained in high yields at room temperature while Bis-tetracene-diones are prepared upon heating. Both products display interesting fluorescence properties in the visible range with quantum yields varying from 50 to 60 %.

Stable 2D Bisthienoacenes: Synthesis, Crystal Packing, and Photophysical Properties

“…Four TIPS substituents are located at the 1, 6, 7, and 12 positions of the bisthienotetracene and bisthienopentacene skeletons (Figure a,b). Because of the steric hindrance between the neighboring TIPS groups, the 2D skeletons are not fully planar but slightly twisted, which is similar to the previously reported bistetracenes (Figure S1 in the Supporting Information) –. The 2D aromatic scaffold of longer conjugated BTP‐4ITPS is more contorted than that of BTT‐4TIPS.…”

“…Eur.J. 2018, 24,14442 -14447 www.chemeurj.org 2018 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim previously reported bistetracenes synthesis, which gave twofold TIPS-substituted bistertracenes as the major product, [10] almostn o1 ,2-addition products from the a,b-unsaturated ketone moieties (i.e.,c ompounds 4 and 7)c ould be isolated even if less than one equivalent of triisopropylsilylethynyl (TIPS) lithiumw as used. This might due to extended conjugation of the more electron-rich thiophenea nd benzo[b]thiophene units with the fused p-system, which made the subsequent 1, 4-addition [11d] on the 6,12-positionseasier.…”

“…Recently,aseries of bistetracenes, for example tetraceno [2,1,12,11-opqra]tetracene (BT-III, Figure 1b), have received increasing attention. [10] According to our previous work, we found that the photophysical and electrochemical properties as well as packing modes can be dramaticallyt uned by varying the number of triisopropylsilylethynyl (TIPS) substituents. [10c] However, the influence of heteroatoms on the properties of 2D conjugated acenes remains elusive.…”

“…To our surprise, different from previous reported bistetracenes, [10b, c] only four-fold TIPS-substitutedp roducts were isolated, indicating both 1,2-and1 ,4-additiono ccurred at the a,b-unsaturated ketonem oieties( highlighted in dashed ovals, Scheme 1). [10,11] The electrochemical and optical properties, crystalp acking, and charge carrier transportp roperties were investigated in detail.…”

Synthesis and Properties of Benzo‐Fused Indeno[2,1‐c]fluorenes

“…Diones 9 [19] and 10, [20] the precursors of 5 and 6,r espectively,c an be prepared via the previously reported pathway of Diels-Alder cycloaddition of the requisite cyclopentadienone followed by cheletropic elimination of CO and then "inside-out" Friedel-Crafts acylation onto the outer benzenes. Alternatively,w ee xplored the "outside-in" Friedel-Crafts route as well to avoid the sometimes-difficult task of cyclopentadienone formation.A ss hown in Scheme 1, Suzukic ross-coupling of naphthalene 11 [21] to ester 12 furnished diester 13,w hich could be cyclized with TfOH [22] to give dione 10.A ddition of the lithiated nucleophile to either 9 or 10 followed by SnCl 2mediated reductive dearomatization [23] of the central arene afford the desired [2,1-c]IF derivatives as green-black solids. Whereas the SnCl 2 reactionp roceeded smoothly at room temperaturef or 5a and 6a,t he addition of catalytic TFAw ith moderate heating (50-80 8C) wasn ecessary fort he successful generation of the arylated systems.…”