Cycloisomerization of Oxindole-Derived 1,5-Enynes: A Calcium(II)-Catalyzed One-Pot, Solvent-free Synthesis of Phenanthridinones, 3-(Cyclopentenylidene)indolin-2-ones and 3-Spirocyclic Indolin-2-ones

Abstract

Calcium-catalyzed regioselective synthesis of oxindole-derived 1,5-enynes, followed by cycloisomerization, from readily accessible 3-hydroxy-3-(alkynyl)indolin-2-ones and styrenes in one-pot, under solvent-free conditions is described. This method offers the synthesis of diverse molecules: phenanthridinones, 3-(cyclopentenylidene)indolin-2-ones, and 3-spirocyclic indolin-2-ones are obtained through cascade reactions including cross-dehydrative-coupling, [3,3]-sigmatropic rearrangement, carbocyclization, isomerization, oxidative-ring rearrangement, and Diels-Alder cycloaddition. In addition, this method features atom- and step-economy, broad substrate scope, and high yields. (Figure presented.).