Pyrazolidinone-Aided Ru(II)-Catalyzed Regioselective C–H Annulation with Allenes
Geetanjali S. Sontakke, Atul Chaturvedi, Debasish Jana, Chandra M. R. Volla
Abstract
Regioselective annulation of allenes via C–H activation represents an elegant synthetic approach toward the construction of valuable scaffolds. Considering the importance of allenes, herein we developed an unprecedented Ru(II)-catalyzed highly regioselective redox-neutral C–H activation/(4 + 1)-annulation of 1-arylpyrazolidinones employing allenyl acetates to access pyrazolo[1,2- a ]indazol-1-one derivatives. Additionally, allenyl cyclic carbonates, which were never tested in C–H activation, were utilized to construct a similar class of heterocycles having a pendent alcohol functionality. Notably, double C–H functionalization was achieved by a simple modification of reaction conditions. The synthetic significance of this methodology is underscored by late-stage modification of natural products, broad substrate scope, gram-scale synthesis, and postfunctionalizations.