Carbocatalysed Oxidative Csp2-Csp2 Homocouplings of Benzo-Fused Heterocycles

Tom Wirtanen, Mikko K. Mäkelä, Jawad Sarfraz, Petri Ihalainen, Sami Hietala, Michele Melchionna, Juho Helaja

    Research output: Contribution to journalArticleScientificpeer-review

    21 Citations (Scopus)

    Abstract

    Appropriate and fine-tuned treatments of amorphous carbon (AC) involving aqua regia or concentrated HNO3 lead to oxidised carbon materials (oAC) which are able to catalyse 2,2′- and 3,3′-homocouplings of various functionalised indoles with outstanding activity. This newly developed carbocatalysed Csp2-Csp2 bond formation can be achieved under mild thermal conditions. The study on the scope of the reaction revealed that the reaction can be extended to the homocoupling of other substrates of high synthetic interest such as 2-naphthol, 2-functionalised benzofurans and benzothiofurans. The characterisation of oAC with XPS together with ad hoc experiments aimed at blocking the active site revealed that the presence and distribution of C=O functionalities is critical and correlates well with the catalytic activity. Such experiments provide solid support for elucidation of the mechanism, suggesting a quinone nature of the active C=O groups, which are spontaneously regenerated by oxygen. This is confirmed by the fact that 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is able to promote the coupling in a stoichiometric fashion.
    Original languageUndefined/Unknown
    Pages (from-to)3718–3726
    JournalAdvanced Synthesis and Catalysis
    Volume357
    Issue number16-17
    DOIs
    Publication statusPublished - 2015
    MoE publication typeA1 Journal article-refereed

    Keywords

    • heterogeneous catalysis

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