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In 2012, Yu and coworkers devised the first effective U‐shaped nitrile‐based directing template that was covalently linked to the toluene derivatives via a removable benzyl ether linkage (Scheme 2.3) [11]. Notably, the directing ability of the template was improved by installing two isobutyl templates at the α‐position adjacent to the linearly chelating nitrile template due to the Thorpe–Ingold effect. This directing template efficiently enabled the meta‐C–H olefination of a broad range of toluene derivatives using Pd(OPiv)₂ as the catalyst and AgOPiv as the oxidant. It is worth mentioning that such remote C–H activation that possibly demanded a cyclophane‐like 11‐membered palladacycle was first ever disclosed. Remarkably, the intrinsic electronic and steric biases of the substrates were successfully overridden. Finally, the directing template was readily cleaved through hydrogenolysis with a Pd/C catalyst.

Scheme 2.3 meta‐C–H activation of toluene derivatives.

Source: Modified from Leow et al. [11].