Diarylmethanes have received great synthetic interests because they are found ubiquitously in pharmaceuticals, biologically active compounds, and supramolecular structures. A classical approach to prepare these motifs is Lewis-acid mediated Friedel-Crafts (or SEAr reactions) with arenes and benzylic electrophiles. However, these valuable processes are often associated with several limitations, including i) their restrictions to electron-rich arenes, ii) their low tolerance to acid-sensitive functional groups, iii) their low chemo- and regio-selectivities. The transition-metal catalyzed cross-coupling reactions of a stoichiometric organometallic aryl with benzyl halides have emerged as alternatives to the Friedel-Crafts reactions. However, this �prefunctionalization� process suffers from the requirement of additional steps for preparation of organometallic reagents and the compatibility of functional groups. To avoid preactivation step, transition-metal catalyzed direct benzylation of electron-deficient pentafluoroarenes and heteroarenes have been successfully developed. However, directing-group assisted ortho-benzylation of arenes by C-H bond activation is not known. We have developed a palladium-catalyzed ortho-benzylation of benzamides with benzyl halides directed by the amide group to afford diarylmethanes, which can be further functionalized to other diarylmethane derivatives.

Palladium-catalyzed direct<i> ortho</i>-benzylation of benzamides

246th National Meeting (2013)

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Palladium-catalyzed direct ortho-benzylation of benzamides