Selective ortho-C−H Activation in Arenes without Functional Groups

Chan, Antony and Jakoobi, Martin and Wang, Chenxu and O'Neill, Robert and Aydin, Gulsevim and Halcovitch, Nathan and Boulatov, Roman and Sergeev, Alexey (2022) Selective ortho-C−H Activation in Arenes without Functional Groups. Journal of the American Chemical Society, 144 (26). 11564–11568. ISSN 0002-7863

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Abstract

Aromatic C-H activation in alkylarenes is a key step for the synthesis of functionalised organic molecules from simple hydrocarbon precursors. Known examples of such C-H activations often yield mixtures of products resulting from activation of least-hindered C-H bonds. Here we report highly selective ortho-C-H activation in alkylarenes by simple iridium complexes. We demon-strate that the capacity of the alkyl substituent to override the typical preference of metal-mediated C-H activation for least hindered aromatic C-H bonds results from transient insertion of iridium into the benzylic C-H bond. This enables fast iridium insertion into the ortho-C-H bond, followed by regeneration of the benzylic C-H bond by reductive elimination. Bulkier alkyl substituents increase ortho-selectivity. The described chemistry comprises a conceptually new alternative to existing approaches to aromatic C-H bond activation.