Synthesis of Spirocyclic Isoindolones Using an Alkynyl -Prins/Oxidative -Nazarov Cyclization Sequence.

In this report, we describe an alkynyl --Prins cyclization of 3-hydroxyisoindolones to prepare -Prins products. These Prins adducts undergo oxidation at the 3-isoindolone position after activation of the amide by triflic anhydride and 2-chloropyridine to form a pentadienyl cation capable of undergoing a -Nazarov cyclization. Using this methodology, angular-fused N-heterocyclic small molecules with two new rings, two new carbon-carbon bonds, a vinyl halide, and an -tertiary stereocenter can be obtained in good yields.