Activation of remote meta-C-H bonds assisted by an end-on template

Article

关键词: CARBON-HYDROGEN BONDS;    ROOM-TEMPERATURE;    ARYLATION;    OLEFINATION;    CATALYST;    ARENES;    FUNCTIONALIZATION;    SELECTIVITY;    REACTIVITY;    COMPLEXES;   

DOI  :  10.1038/nature11158

来源: SCIE

【 摘 要 】

Functionalization of unactivated carbon-hydrogen (C-H) single bonds is an efficient strategy for rapid generation of complex molecules from simpler ones. However, it is difficult to achieve selectivity when multiple inequivalent C-H bonds are present in the target molecule. The usual approach is to use sigma-chelating directing groups, which lead to ortho-selectivity through the formation of a conformationally rigid six- or seven-membered cyclic pre-transition state(1-14). Despite the broad utility of this approach, proximity-driven reactivity prevents the activation of remote C-H bonds. Here we report a class of easily removable nitrile-containing templates that direct the activation of distal meta-C-H bonds (more than ten bonds away) of a tethered arene. We attribute this new mode of C-H activation to a weak 'end-on' interaction(15) between the linear nitrile group and the metal centre. The 'end-on' coordination geometry relieves the strain of the cyclophane-like pre-transition state of the meta-C-H activation event. In addition, this template overrides the intrinsic electronic and steric biases as well as ortho-directing effects with two broadly useful classes of arene substrates (toluene derivatives and hydrocinnamic acids).

【 授权许可】

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