Metal-Catalyzed/Metal-Free Sp~2/sp~3 C-H Functionalization

The C-H bond is one of fundamental bonds in organic compounds, as well as the most simple functional group. It can be transformed into C-C bond or C-X bond via C-H functionalization, without the prefunctionalization of substrates, which decreases the amount of reaction steps remarkably. C-H functionalization requires less metal catalyst and releases less waste gas or solvent, which means increase of atom economy. It has been one of the important tools in organic synthetic chemistry. This paper reports three methods for sp3 C-H functionalization under metal or metal-free condition. Meanwhile, a method for sp2 C-H functionalization catalyzed by transition metal is developed.Details are listed as below:1. A new synthetic strategy for C-C bond formation has been developed via a free radical cascade process under metal-free condition. Activation of inert sp3 C-H/elimination of SO2/C-C bond formation were involved in this system. A direct access to alkylated propanamide was provided.2. A metal-free radical tandem oxidative sp3 C-H bond functionalization of alkanes and dearomatization of N-phenyl-cinnamamides was developed, which provided a direct access to alkylated 1-azaspiro[4.5]decanes with excellent regioselectivity and diastereoselectivity. Meanwhile, the same strategy was applied to cyanoalkylation of N-phenyl-cinnamamides, which provided a direct access to cyanoalkylated 1-azaspiro [4.5]decanes with good regioselectivity and diastereoselectivity.3. A silver-catalyzed cascade radical cyclization of N-phenyl-cinnamamide with diphenylphosphine oxide was reported, providing a direct approach to 3,4-disubstituted dihydroquinolin-2(1H)-ones through activation of the P-H bond and functionalization of the sp3 C-H bond.