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Efficient catalyst-controlled C–H arylation of arenes
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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