Abstract
Given that C-H bonds are ubiquitous in organic compounds, substrate functionalization via C-H bond activation appears as a challenging straightforward method in organic synthesis, eliminating the multiple steps and limitations associated with the preparation of functionalized starting materials. Regioselectivity is the important issue to be addressed in the transformation of C-H bonds because organic molecules can have many different types of C-H bonds. The use of a directing group can largely overcome the issue of regio-control by allowing the catalyst to come into close proximity to the targeted C-H bonds which, in most cases, are ortho C-H bonds. A wide variety of functional groups has been evaluated as directing groups to date in the transformation of C-H bonds. The development of new types of directing groups continues to be important, in terms of exploring novel types of transformations of C-H bonds that cannot be achieved by conventional directing groups. In 2005, Daugulis reported the arylation of unactivated C(sp3)-H bonds using 8-aminoquinoline and picolinamide as a N,N-bidentate directing group in conjunction with Pd(OAc)2 as the catalyst. Encouraged by these promising results, a number of transformations of C-H bonds have since been developed using bidentate directing group systems. In this review, a recent advance on chelation-assisted transformation of C-H bonds by taking advantage of a bidentate directing group is described.
