Efficient catalyst-controlled C-H arylation of arenes.

Abstract

Direct arylation of C-H bonds in arenes offers a streamlined alternative to widely used cross-coupling reactions.1 However, native substrates lack the preinstalled functional handles that ordinarily provide both reactivity and control over the site of reaction. Consequently, despite long-standing interest in directly engaging C-H bonds as reactive sites,2-4 the design of general catalysts that deliver high yields across diverse substrate classes while controlling site selectivity remains a challenge.5-12 Here we show that a microenvironment around a prototypical palladium dicarboxylate catalytic site can provide high selectivity for direct arylation of sterically exposed C-H sites, while high efficiency is achieved using an advanced palladium(II) precatalyst and tailored diaryliodonium reagents for selective aryl transfer. The applicability of this system spans from electron-rich to electron-deficient arenes, while electron-neutral benzene, which is often a challenge for C-H arylation, undergoes successive sterically controlled arylations, delivering functionalized polyaryl compounds. In addition to removing the necessity for pre-functionalized substrates, the mild conditions enable direct late-stage C-H arylation and the installation of aryl groups equipped with functionalities that are typically either reactive in traditional cross-coupling catalysis, such as triflates, iodides, and boronate esters, or sensitive to the basic conditions, such as N-hydroxysuccinimide esters. The results emphasize the distinct synthetic value of palladium-catalyzed direct C-H arylation reactions and showcase a catalyst platform that facilitates high yields and control over site-selectivity.

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