Access to Functionalized Pyrenes, Peropyrenes, Terropyrenes, and Quarterropyrenes via Reductive Aromatization

Abstract

Herein we report a versatile concept for the synthesis of fourfold functionalized, soluble pyrenes, peropyrenes, terropyrenes, and quarterropyrenes. They were obtained by a modular stepwise approach towards the rylene scaffold via Suzuki-Miyaura cross coupling, oxidative cyclodehydrogenation in the presence of caesium hydroxide under air, and finally zinc-mediated reductive silylation. The silylated reaction products were characterized by X-ray crystallography. The first example of a synthesized and crystallized quarterropyrene is presented and its oxidation reaction investigated. The functionalized ropyrenes were systematically characterized by means of UV/Vis-NIR and photoluminescence spectroscopy showing a bathochromic shift of 80 nm per naphthalene unit and a nearly linear increase of the extinction coefficients. Cyclic voltammograms and DFT calculations identify them as electron-rich dyes and show a narrowing of the electrochemically determined HOMO-LUMO gap and lower oxidation potentials for the higher homologues.

Tetrasubstituted Peropyrenes Formed by Reductive Aromatization: Synthesis, Functionalization and Characterization

“…The moderately air sensitive orange solid 2 could be easily purified from zinc dichloride and excess zinc by dissolving the crude product in dichloromethane, filtration and removing the solvent, since the polymeric zinc chloride dioxane adduct is insoluble in chlorinated solvents. [38] An air stable product can be obtained, when 1 is reacted with triisopropylsilyl chloride (TIPSCl) instead of TMSCl. Notable, a moderate yield of 20 % of peropyrene 3 could only be achieved by using imidazole as equimolar activation reagent for triisopropylsilyl chloride.…”

“…Recently, we demonstrated the potential of a reductive O‐silylation strategy in the synthesis of peropyrene's higher homologues, terropyrene and quarterropyrene. [38] As a key step, we modified and applied the reductive aromatization step recently reported for the reductive functionalization of perylene diimide (PTCDI)[ 39 , 40 ] by using Zn instead of Na as bench stable and less powerful reducing agent. In the following we add proof, that this protocol is perfectly suitable for the introduction of different functional groups via post‐functionalization of reactive triflyl and pivaloyl peropyrene key intermediates (Scheme 2 c).…”

2,9‐Diazadibenzoperylene and 2,9‐Dimethyldibenzoperylene‐1,3,8,10‐tetratriflates: Key to Functionalized 2,9‐Diazaperopyrenes

“…Our method comprises a reductive functionalization at the carbonyl positions of one of the most prominent organic dyes in photo chemistry and physics, perylenetetracarboxylic diimide (PTCDI) and the introduction of four replaceable and versatile triflate substituents. We also demonstrated a reductive silylation and functionalization approach of peropyrenes higher homologues terropyrene and quarterropyrene [28] . Independently, Miyake et al.…”

“…We also demonstrated a reductive silylation and functionalization approach of peropyrenes higher homologues terropyrene and quarterropyrene. [28] Independently, Miyake et al reported a reductive transformation of naphthalene tetracarboximide (NTCDI) and PTCDI to tetrapivaloyl substituted 2,7-diazapyrenes and DDPs utilizing zinc or manganese as reducing agents. [29][30][31] Two examples of Ni-catalyzed Suzuki-Miyaura cross-coupling reactions of such 2,9-diazaperopyrenetetrapivaloates with a fourfold molar excess of two aryl boronic acids toward 2,9-diaza-1,3,8,10-tetra(4-tert-butylphenyl)-peropyrene (65 % yield) and -tetra(5-methylthienyl)-peropyrene (10 % yield) were reported.…”

“…We also demonstrated a reductive silylation and functionalization approach of peropyrenes higher homologues terropyrene and quarterropyrene. [28] Independently, Miyake et al. reported a reductive transformation of naphthalene tetracarboximide (NTCDI) and PTCDI to tetrapivaloyl substituted 2,7‐diazapyrenes and DDPs utilizing zinc or manganese as reducing agents.…”