Scalable, Chromatography-Free Synthesis of Alkyl-Tethered Pyrene-Based Materials. Application to First-Generation “Archipelago Model” Asphaltene Compounds

Abstract

In this paper, we report a highly efficient, scalable approach to the total synthesis of conformationally unrestricted, electronically isolated arrays of alkyl-tethered polycyclic aromatic chromophores. This new class of modular molecules consists of polycyclic aromatic "islands" comprising significant structural fragments present in unrefined heavy petroleum, tethered together by short saturated alkyl chains, as represented in the "archipelago model" of asphaltene structure. The most highly branched archipelago compounds reported here share an architecture with first-generation dendrimeric constructs, making the convergent, chromatography-free synthesis described herein particularly attractive for further extensions in scope and applications to materials chemistry. The syntheses are efficient, selective, and readily adaptable to a multigram scale, requiring only inexpensive, "earth-abundant" transition-metal catalysts for cross-coupling reactions and extraction and fractional crystallization for purification. This approach avoids typical limitations in cost, scale, and operational practicality. All of the archipelago compounds and synthetic intermediates have been fully characterized spectroscopically and analytically. The solid-state structure of one archipelago model compound has been determined by X-ray crystallography.

Unexpected Michael Additions on the Way to 2.3,8.9‐Dibenzanthanthrenes with Interesting Structural Properties

“…With this goal in mind, we developed an efficient three‐step route to the key intermediate, 5,11‐diethyl‐2.3,8.9‐dibenzanthanthrene‐1,7‐dione 1 (Scheme ). Starting from the known C s ‐symmetric pyrene derivative 2 (see the Supporting Information for crystallographic analysis), a double Suzuki cross‐coupling with boronic ester 3 under microwave‐assisted conditions gave methyl ester product as a mixture of diastereomers 4 a‐Me and 4 b‐Me (Scheme ). The transformation was sensitive to both reaction time and stoichiometry.…”

“…[1] With this goal in mind, we developed an efficient three-step route to the key intermediate, 5,11-diethyl-2.3,8.9-dibenzanthanthrene-1,7-dione 1 (Scheme 1). Starting from the known C s -symmetric pyrene derivative 2 (see the SupportingI nformationf or crystallographic analysis), [11] ad ouble Suzuki cross-coupling with boronic ester 3 under microwave-assisted conditions gave methyl ester product as am ixture of diastereomers 4a-Me and 4b-Me (Scheme 1). The transformation was sensitive to both reaction time and stoichiometry.I nitialr eaction attempts using 2.5 equiv of 3 (1.25 equiv per bromide moiety)p rovided mainlyt he mono-coupled product after reactionf or 8h,a long with unreacted 2 and the desired product 4a,b-Me (see the Supporting Information for detailsa nd crystallographic analysis of mono-additionp roduct).…”

Molecular Packing and Solid‐State Photophysical Properties of 1,3,6,8‐Tetraalkylpyrenes

“…Twelve pyrenes with four linear alkyl groups at the 1‐, 3‐, 6‐, and 8‐positions (Alkyl=Me, Et, Pr, Bu, Pen, Hex, Hep, Oct, Non, Dec, Und, or Dod) were synthesized through Kumada–Tamao–Corriu cross‐coupling reaction of 1,3,6,8‐tetrabromopyrene with corresponding alkyl Grignard reagents and were obtained in moderate yields (Scheme ) . The prepared 1,3,6,8‐tetraalkylpyrenes were purified by successive silica gel column chromatography, size exclusion chromatography, and recrystallization prior to photophysical analyses.…”

Model Asphaltenes Adsorbed onto Methyl- and COOH-Terminated SAMs on Gold

“…Model Compounds. Samples of AcChol-Th, 19 AcChol-Ph, 19 and 1,6-DiEtPy[Bu-Carb] 20 were synthesized as previously described.…”