A walk around the application of nanocatalysts for cross-dehydrogenative coupling of C-H bonds.

Cross-dehydrogenative coupling reactions between two unmodified C-H bonds are one of the most attractive and fundamental strategies for the construction of C-C bonds. As these reactions avoid pre-functionalization and de-functionalization of the substrates, they are cleaner, safer, and faster than traditional cross-coupling reactions. After the introduction of the modern area of cross-dehydrogenative coupling in 2003, many efforts have been devoted to the development of more efficient and selective catalytic systems for these appealing reactions. Among the different types of catalytic systems that have been investigated, nanostructured metal catalysts are highly attractive in view of their high catalytic performance, easy separability and good reusability. The purpose of this review is to focus on the application of nanocatalysts for cross-dehydrogenative coupling of C-H bonds with particular emphasis on the mechanistic aspects of the reactions. Specifically, we have structured this review based on the type of C-C bonds. Thus, the review is divided into six major sections: (i) C(sp 3 )-C(sp 3 ) coupling; (ii) C(sp 3 )-C(sp 2 ) coupling; (iii) C(sp 3 )-C(sp) coupling; (iv) C(sp 2 )-C(sp 2 ) coupling; (v) C(sp 2 )-C(sp) coupling; and (vi) C(sp)-C(sp) coupling.