Diverse ortho-C(sp2)–H Functionalization of Benzaldehydes Using Transient Directing Groups

Pd-catalyzed C–H functionalizations promoted by transient directing groups remain largely limited to C–H arylation only. Herein, we report a diverse set of ortho-C(sp2)–H functionalizations of benzaldehyde substrates using the transient directing group strategy. Without installing any auxiliary directing group, Pd(II)-catalyzed C–H arylation, chlorination, bromination, and Ir(III)-catalyzed amidation, could be achieved on benzaldehyde substrates. The transient directing groups formed in situ via imine linkage can override other coordinating functional groups capable of directing C–H activation or catalyst poisoning, significantly expanding the scope for metal-catalyzed C–H functionalization of benzaldehydes. The utility of this approach is demonstrated through multiple applications, including late-stage diversification of a drug analogue.