Transition Metals and Transition Metals/Lewis Acid Cooperative Catalysis for Directing Group Assisted para-C-H Functionalization

In the past few decades, synthetic organic chemistry has been invigorated with the development of transition metal catalyzed directing group assisted regioselective C-H functionalization. Although this approach started its journey with ortho-C-H functionalization its steady advancement has succeeded in providing distal para-C-H activation. All the challenges to reach distal para-C-H bonds through the formation of a macrocyclic transition state are addressed by this strategy to a great extent. In a complementary approach, transition metal and Lewis acid cooperative catalysis were exploited to accomplish site-selective para-C-H functionalization. In the last few years, these approaches delivered an ample number of reports which have emerged as an alternative to the traditional para-electrophilic/nucleophilic functionalizations of arenes. In this review, we compile those achievements to provide a quick overview in the field of directing group assisted para-selective C-H functionalization.