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

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. magnified image