Asphaltene oxide promotes a broad range of synthetic transformations

Abstract

Carbocatalysts, which are catalytically-active materials derived from carbon-rich sources, are attractive alternatives to metal-based analogs. Graphene oxide is a prototypical example and has been successfully employed in a broad range of synthetic transformations. However, its use is accompanied by a number of practical and fundamental drawbacks. For example, graphene oxide undergoes explosive decomposition when subjected to elevated temperatures or microwaves. We found that asphaltene oxide, an oxidized collection of polycyclic aromatic hydrocarbons that are often discarded from petroleum refining processes, effectively overcomes the drawbacks of using graphene oxide in synthetic chemistry and constitutes a new class of carbocatalysts. Here we show that asphaltene oxide may be used to promote a broad range of transformations, including Claisen-Schmidt condensations, CC cross-couplings, and Fischer indole syntheses, as well as chemical reactions which benefit from the use of microwave reactors.

Soluble asphaltene oxide: a homogeneous carbocatalyst that promotes synthetic transformations

“…We previously showed that asphaltene-based carbocatalysts feature an advantage over their graphene analogues in that they can be utilized in microwave-assisted chemistry. 17 Building on these results, we focused on employing sAO in microwaveassisted Fischer indole syntheses. Indole derivatives have a Unless otherwise noted, all reactions were performed using 1.2 mmol of phenylhydrazine, 1.0 mmol of cyclohexanone, 2.0 mL of water as solvent and the indicated quantity of catalyst loading at 150 C in a microwave reactor.…”

“…We recently reported a new carbocatalyst based on asphaltene. 17 While the structure of asphaltene is reminiscent of a graphene sheet, it is relatively small. 18 Subjecting asphaltene to a modied Hummers' method afforded asphaltene oxide (AO), which was found to exhibit catalytic activities similar to that of GO but under a wider range of conditions.…”

Recent Advances in the Unconventional Design of Electrochemical Energy Storage and Conversion Devices

“…This clear separation increased the solubility and widened the window of redox potential by more than 0.4 V [87]. The redox potentials and solubility of organic redox molecules can be engineered by attaching positively charged and negatively charged functional groups to the aromatic rings [88]. The position of side groups determined the redox potential and solubility in organic redox species [89].…”

Carbon Materials as Catalytic Tools for Oxidative Dehydrogenations and Couplings in Liquid Phase

“…The scope of the reaction includes aliphatic and aromatic amines, while the latter tolerate both electron withdrawing and electron donating substituents, including halogens, with yields ranging between 17% and 77%. Bielawski and coworkers recently developed a new class of carbocatalysts, asphaltene oxides (AOs) 85 , which are prepared from the asphaltene waste generated during crude oil refining process. Structurally, AO is a truncated analog of GO with lower oxygen content (Scheme 31).…”