Challenge and progress: palladium-catalyzed sp3 C–H activation

Abstract

Palladium-catalysis has been broadly applied to sp² C–H activation. Recently, palladium-catalyzed sp³ C–H activation has also been considered as an important strategy to construct synthetically useful C–C/C–X bonds. Allylic sp³ C–H bonds can be successfully activated by Pd(II) species to produce η³-coordinated palladium species for further transformations, while activation of general sp³ C–H bonds mainly proceeds through directed pathways with the assistance of proper directing groups or initiated by oxidative addition. Various catalytic mechanisms were extensively investigated through either Pd(II)/Pd(0), Pd(II)/Pd(IV) or Pd(0)/Pd(II) catalytic cycles. The challenges faced in this area have also been addressed in this perspective article.