new cobalt-catalyzed phenolic OH-assisted C–H functionalization of 2-vinylphenols with allenes to give various 2H-chromenes is described. It is the first time that allenes are used as the coupling partners in the cobalt-catalyzed C–H activation reactions. In most cases, cobalt-catalyzed oxidative annulation of arenes with alkenes or alkynes via C–H activation gave [4 + 2] or [3 + 2] cyclization products
Rh<sup>III</sup>-Catalyzed [4 + 1] Annulations of 2-Hydroxy- and 2-Aminobenzaldehydes with Allenes: A Simple Method toward 3-Coumaranones and 3-Indolinones
method for the regio- and stereoselective synthesis of substituted 3-coumaranones from salicylaldehydes and allenes using a rhodium(III) catalyst has been developed. This procedure gives access to new 2-vinyl-substituted 3-coumaranone compounds. The method involves a RhIII-catalyzed aldehyde C–H activation and annulationreactions. Moreover, this RhIII-catalyzed [4 + 1] annulationreaction has been applied
A cobalt‐catalyzed oxidative annulation of amides with allenes to provide isoquinolin‐1(2H)‐ones and pyridones was explored. The new catalytic reaction proceeded through aminoquinoline‐directed C−H activation followed by unusual regioselective insertion, annulation, and isomerization. A variety of functionalized amides and allenes were converted into the corresponding products under mild reaction