Synthesis of Rhazinicine by a Metal-Catalyzed CH Bond Functionalization Strategy

C-H activation: a complementary tool in the total synthesis of complex natural products

The recent advent of transition-metal mediated C-H activation is revolutionizing the synthetic field and gradually infusing a "C-H activation mind-set" in both students and practitioners of organic synthesis. As a powerful testament of this emerging synthetic tool, applications of C-H activation in the context of total synthesis of complex natural products are beginning to blossom. Herein, recently completed total syntheses showcasing creative and ingenious incorporation of C-H activation as a strategic manoeuver are compared with their "non-C-H activation" counterparts, illuminating a new paradigm in strategic synthetic design.

Amide-directed tandem C-C/C-N bond formation through C-H activation

The transformation of C-H bonds into other chemical bonds is of great significance in synthetic chemistry. C-H bond-activation processes provide a straightforward and atom-economic strategy for the construction of complex structures; as such, they have attracted widespread interest over the past decade. As a prevalent directing group in the field of C-H activation, the amide group not only offers excellent regiodirecting ability, but is also a potential C-N bond precursor. As a consequence, a variety of nitrogen-containing heterocycles have been obtained by using these reactions. This Focus Review addresses the recent research into the amide-directed tandem C-C/C-N bond-formation process through C-H activation. The large body of research in this field over the past three years has established it as one of the most-important topics in organic chemistry.

Constructing multiply substituted arenes using sequential palladium(II)-catalyzed C-H olefination

Complementary catalytic systems have been developed in which the reactivity/selectivity balance in Pd(II)-catalyzed ortho -C–H olefination can be modulated through ligand control. This allows for sequential C–H functionalization for the rapid preparation of 1,2,3-trisubstituted arenes. Additionally, a rare example of iterative C–H activation, in which a newly installed functional group directs subsequent C–H activation has been demonstrated.

Palladium(II)-catalyzed C-H activation/C-C cross-coupling reactions: versatility and practicality

In the past decade, palladium-catalyzed C-H activation/C-C bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming C-C bonds from C-H bonds: Pd(II)/Pd(0), Pd(II)/Pd(IV), Pd(0)/Pd(II)/Pd(IV), and Pd(0)/Pd(II) catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of C-H bonds with organometallic reagents through a Pd(II)/Pd(0) catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.