Pristine Facet of Alkynyl-Prins Vinyl Carbocations for the Functionalization of Inactivated C(sp ³ )–H Bonds: A Highly Selective [1,5]-Hydride Migration vs. Concerted C–H Insertion

Selective functionalization of inactivated C(sp³)-H bonds is an important and useful strategy; at the same time, it is a very challenging task due to the presence of similar C(sp³)-H bonds in a single organic molecule. Herein we report an unprecedented domino process for the functionalization of inactivated C(sp³)-H bonds by employing alkynyl-Prins vinyl carbocations as the key tool. This strategy provided rapid and efficient access to diverse polycyclic-bridged systems. The reaction is very regioselective between <i>sec</i>-C-H vs. <i>tert</i>-C-H bonds and stereoselective between diastereotopic C-H bonds. An interception of the sp²-carbocation intermediate and isolation of the related olefin-ketone strongly supported the [1,5]-hydride migration from β-C-H to the vinyl carbocation over the concerted C-H insertion. The reaction involves small molecule (TfOH) catalysis and a domino strategy for the construction of 1C-O and 2C-C bonds.