A powerful new construction of complex chiral polycycles by an indium(III)-catalyzed cationic cascade.

InI(3) and InBr(3) have been found to be effective catalysts for the π activation of C≡C bonds to initiate the conversion of chiral propargylic alcohols or silyl ethers to polycyclic products in excellent yields and with high stereoselectivity. The method has been applied to the synthesis of chiral fused hexacyclic ring systems with the creation of multiple new stereocenters. The power and scope of the method are illustrated by a variety of examples.