Organic synthesis chelation-assisted

Catalytic C-C bond formation via sp- C-H bond cleavage represents the ultimate reaction in organic synthesis. A relatively ideal catalytic reaction system involves the use of sp3 C-H bonds adjacent to a heteroatom such as nitrogen and oxygen atoms. Recently, Jim et al. [69] succeeded in the Ru3(CO)12-catalyzed alkylation of an sp3 C-H bond a to the nitrogen atom in benzyl-(3-methyl-2-pyridinyl)amine by means of chelation assistance (Eq. 43). In this case, the coordination of the pyridine nitrogen to the ruthenium complex followed by C-H... 

An important factor in the success of these reactions involves chelation-assistance by a heteroatom. Thus, the coordination of the heteroatom to the metal, brings the metal closer to the C-H bond and stabilizes the thermally unstable C-M-H species formed by the oxidative addition of a C-H bond to a low-valent transition metal complex. In addition, the use of the chelation-assistance leads to a high regioselectivity, which is an essential factor in organic synthesis. For reactions, a number of transition metal complexes - including ruthenium, rhodium, and iridium - are used as a catalyst, and ruthenium-catalyzed reactions will be described in this chapter [5]. 

Overall, the field of chelate-assisted C-H bond functionalization has evolved dramatically over the last 10 years and is expected to contribute even more to streamlining organic synthesis and enabling efficient synthetic methodologies in the years to come. The following chapter will cover developments in the area of nonchelate-assisted C-H bond functionalizations, some of which have been mentioned briefly in this chapter. 

---