Synthesis of Spirocyclic Isoindolones Using an Alkynyl <i>aza</i>-Prins/Oxidative <i>halo</i>-Nazarov Cyclization Sequence

Abstract

In this report, we describe an alkynyl halo-aza-Prins cyclization of 3-hydroxyisoindolones to prepare aza-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 halo-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 aza-tertiary stereocenter can be obtained in good yields.