Cationic Iridium-Catalyzed Synthesis Initiated by the Cleavage of C-H, N-H, and C-O Bonds

The direct functionalization of inactive bonds is an ideal transformation in organic synthesis because the introduction of activating groups, such as halogens and metals, to substrates is unnecessary and by-products derived from them are not formed. This report describes several types of cationic iridium-catalyzed reactions that occur through C-H, N-H, or C-O bond cleavage. The carbonyl-directed sp2 C-H bond activation of aryl ketones realized new approaches to benzofulvene, benzofuran and indole synthesis, as well as the C2-position-selective alkylation of N-acyl-protected indoles. The enantioselective sp3 C-H alkylation of 2-(alkylamino)pyridines and the intermolecular enantioselective hydroamination of heteroaromatic amines gave various chiral amines. O-to-N-alkyl migration in 2-alkoxypyridines gave N-alkylpyridones via C-O bond cleavage.