Contorted aromatics via a palladium-catalyzed cyclopentannulation strategy

Abstract

A palladium-catalyzed cyclopentannulation provides access to contorted aromatics that afford solubility benefits while maintaining pi–pi stacking motifs.

Stabilizing Pentacene By Cyclopentannulation

“…From the Clar sextet representation, the electronic structure of 3 should be similar to that of anative pentacene with asingle migrating p sextet ( Figure 1). Owing to our recent interest in cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs), [22][23][24][25][26] we set out to prepare pentacene derivatives working under the hypothesis that the fusion of five-membered rings would minimize the biradical character at the central carbons leading to stabilized structures.Towards this new class of compounds,we demonstrate herein that cyclopentannulation of ap artially unsaturated pentacene precursor followed by an aromatization step with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) leads to the formation of new pentacenes that are more stabilized than the well-known 6,13-bis(triisopropylsilylethynyl)pentacene (4;TIPS-pentacene). These molecules behave as strong electron acceptors and possess significantly decreased energy gaps.…”

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

“…The optical energy gap of 1 is determined to be 1.78 eV from the onset of its UV-vis absorption spectrum. Similar to the cyclopenta-fused pyrene derivatives [28,29], compound 1 does not show detectable fluorescence emission. Furthermore, the electrochemical properties of 1 was probed by cyclic voltammetry (CV) in DCM (Figure 3b).…”

“…Palladium-catalyzed annulation has been recently proven as an efficient route to get access to aromatic hydrocarbons with peri-fused five-membered rings [25][26][27]. For instance, the dicyclopenta-fused pyrene derivatives ii and iii (Scheme 1) were successfully synthesized through palladiumcatalyzed carbannulation of brominated pyrene with arylacetylenes in good yield [28,29]. However, the larger CP-PAHs beyond the pyrene core, or its extended analogs [30] remain elusive.…”

Cyclopentannulation and cyclodehydrogenation of isomerically pure 5,11-dibromo-anthradithiophenes leading to contorted aromatics

“…[21][22][23][24] We recently became interested in utilizing a palladium-catalyzed cyclopentannulation to create cyclopentafused polycyclic aromatic hydrocarbons (e.g., 1) that could be cyclodehydrogenated to build up contorted aromatics such as 1,2,6,7tetraarylcyclopenta[hi]aceanthrylenes (2, Figure 1). 25 The contorted compounds contain…”

“…The compounds were found to be quite soluble, even with methoxy substituents, yet displayed concentration depended aggregation in solution, and lock-and-key pi-pi stacking in the solid state. 25 We had interest in extending this methodology to elongated aromatics, and attempted to create similar contorted aromatics from our recently described 1,2,8,9tetraaryldicyclopenta[fg,qr]pentacenes (3). 27 Unfortunately, we were not successful in applying a variety of well-known cyclodehydrogenation conditions to facilitate the oxidative C-C bond formation of 3 to give the desired contorted aromatics.…”