Synthesis of extended polycyclic aromatic hydrocarbons by oxidative tandem spirocyclization and 1,2-aryl migration

Abstract

The extended polycyclic aromatic hydrocarbons (PAHs) have received significant interdisciplinary attention due to their semiconducting applications in diverse organic electronics as well as intriguing structural interests of well-defined graphene segments. Herein, a highly efficient oxidative spirocyclization and 1,2-aryl migration tandem synthetic method for the construction of extended polyaromatic hydrocarbons (PAHs) has been developed. The CuCl-catalyst/PhCO3 tBu or DDQ oxidation system in the presence of trifluoroacetic acid enables the selective single-electron oxidation to take place preferentially at the more electron-rich alkene moiety of o-biphenylyl-substituted methylenefluorenes, giving rise to the subsequent tandem process. A variety of structurally diverse extended PAHs including functionalized dibenzo[g,p]chrysenes, benzo[f]naphtho[1,2-s]picene, hexabenzo[a,c,fg,j,l,op]tetracene, tetrabenzo[a,c,f,m]phenanthro[9,10-k]tetraphene, tetrabenzo[a,c,f,k]phenanthro[9,10-m]tetraphene, tetrabenzo[a,c,f,o]phenanthro[9,10-m]picene and S-type helicene have been readily synthesized.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…The in situ 1,2‐aryl shift often changes the course of the oxidative aromatic coupling. Indeed, 1,2‐aryl shifts during the course of oxidative aromatic coupling reactions have been regularly encountered over the last few years . A highly interesting example was published by Müllen and co‐workers during attempts to synthesize tetrabenzo[ a,cd,j,lm ]perylene 156 by the Scholl reaction of 6,7,13,14‐tetraphenylbenzo[ k ]tetraphene 155 (Scheme ) .…”

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

“…[3] Until recently the synthetic chemists were mainly concentrated on the synthesis of alternant NGs, resembling the honeycombf ragment that is, composed exclusively of six-membered rings. [4][5][6][7][8] Meanwhile, the methods allowing the incorporation of pentagons into the large PAH structures till remain rather scarce. [9À11] The synthetic difficulties related to pentagons-bearing structures are mainly associated with the enhanced strain caused by distortion of a p -system and deviationo fv alence angles from the optimal sp 2 -hybridized carbon atoms geometry.N aturally,t hese obstacles tend to exacerbate the synthetic accessibility of PAHs' cores containing severalp entagons even further.N evertheless,p hysical and chemicalp roperties acquired along with pentagons within the aromatic core justify the efforts to develop decent synthetic approaches towards such attractive structures.…”

Clar Covers of Overlapping Benzenoids: Case of Two Identically-Oriented Parallelograms

“…We identify five families of Kekuléan structures: parallelograms M(m 1 + m 2 − µ, n 1 = n 2 ) and M(m 1 = m 2 , n 1 + n 2 − ν) with ZZ polynomials given by Equation (2), generalized ribbons Rb with ZZ polynomials given by Equation (4), horizontally overlapping parallelograms MhM(m 1 , n 1 , m 2 , n 2 , µ, ν) with ZZ polynomials given by Equation (30), intersecting parallelograms MxM(m 2 , n 2 , m 1 , n 1 , µ, ν) with ZZ polynomials given by Equation (35), and vertically overlapping parallelograms MvM(m 2 , n 2 , m 1 , n 1 , µ, ν) with ZZ polynomials given by Equation (20). All formulas are given in the form of multiple sums over binomial coefficients, bearing a close structural similarity to the ZZ polynomial of a pristine parallelogram M(m, n) given by Equation (2). In case of the subset of the composite benzenoids consisting of parallelograms M, generalized ribbons Rb, and vertically overlapping parallelograms MvM, we demonstrate formally the correctness of the derived formulas.…”

“…Benzenoid hydrocarbons are an intensively studied class of aromatic molecules attracting attention of scientists specializing in various fields of chemistry including organic synthesis [1,2] and characterization [3][4][5], combustion chemistry [6,7], nanoscience [8,9], atmospheric chemistry [10,11], astrochemistry [12,13], computational chemistry [14,15], and chemical graph theory [16,17]. Enumeration and construction of Clar covers for benzenoid hydrocarbons constitutes one of the important branches of chemical graph theory.…”