One-shot K-region-selective annulative π-extension for nanographene synthesis and functionalization

Abstract

The optoelectronic nature of two-dimensional sheets of sp2-hydridized carbons (for example, graphenes and nanographenes) can be dramatically altered and tuned by altering the degree of π-extension, shape, width and edge topology. Among various approaches to synthesize nanographenes with atom-by-atom precision, one-shot annulative π-extension (APEX) reactions of polycyclic aromatic hydrocarbons hold significant potential not only to achieve a ‘growth from template’ synthesis of nanographenes, but also to fine-tune the properties of nanographenes. Here we describe one-shot APEX reactions that occur at the K-region (convex armchair edge) of polycyclic aromatic hydrocarbons by the Pd(CH3CN)4(SbF6)2/o-chloranil catalytic system with silicon-bridged aromatics as π-extending agents. Density functional theory calculations suggest that the complete K-region selectivity stems from the olefinic (decreased aromatic) character of the K-region. The protocol is applicable to multiple APEX and sequential APEX reactions, to construct various nanographene structures in a rapid and programmable manner.

New advances in nanographene chemistry

“…127 The direct palladium-catalysed C-H arylation with o-chloranil as the oxidant was shown to occur exclusively at the K-regions of PAHs, which allowed their selective two-step p-extension, for instance, from phenanthrene to dibenzo[g,p]chrysene. 206 Additionally, Scott et al also reported iridiumcatalysed five-fold borylation of corannulene (39) to afford 1,3,5,7,9-pentakis(BPin)corannulene (BPin = (pinacolato)boron), which provided facile access to a defined molecular fragment of [5,5] 206 Additionally, Scott et al also reported iridiumcatalysed five-fold borylation of corannulene (39) to afford 1,3,5,7,9-pentakis(BPin)corannulene (BPin = (pinacolato)boron), which provided facile access to a defined molecular fragment of [5,5] …”

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

“…A variety of synthetic methodologies for constructing various π-extended PAHs have been developed towards achieving high efficiency and novelty56789101112131415. Among them, since the seminal advance has been made by Müllen and Spiess et al .…”

Helically Twisted Tetracene: Synthesis, Crystal Structure, and Photophysical Properties of Hexabenzo[a,c,fg,j,l,op]tetracene

“…Seven isomers including two pairs of enantiomers of 1 could be generated by the combination of the chirality of each [4]helicene moiety (P or M) as shown in Figure 3. The twisted form 1a observed by X-ray crystallography was the most stable conformation among the five ground states 1a-e.…”

“…The end-toend twisted angle of the tetracene moiety of 1 is 80.5°, which is higher than those of previously reported unsubstituted benzannulated acenes. 9 The highly twisted structure of 1 was realized by the combination of four [4]helicene substructures. The packing mode of 1 in the crystal is shown in Figure 2 one-dimensional π-π stacking of the nonplanar π-systems was found.…”

“…3 Recently, we developed a K-region-selective annulative π-extension (APEX) reaction of PAHs as an effective way to grow the π-system of PAHs in a step-economical fashion. 4 We herein report the single-step synthesis of unsubstituted hexabenzo[a,c,fg,j,l,op]tetracene (1) from pyrene and dibenzosilole using our palladium-catalyzed APEX reaction. Helically twisted structure of 1 was revealed by X-ray crystallography.…”