Four-Component Reaction to Access 3,3-Disubstituted Indolines via the Palladium-Norbornene-Catalyzed Ortho Amination/Ipso Conjunctive Coupling

As an important class of multicomponent reactions, the palladium/norbornene (Pd/NBE) cooperative catalysis has been mainly restricted to the coupling of an aryl halide, an electrophile and a nucleophile. Here, we report the development of a Pd/NBE-catalyzed four-component reaction, which involves ortho C-H amination/ipso conjunctive coupling using an alkene and an external nucleophile. The use of alkene-tethered nitrogen electrophiles provides a rapid and modular synthesis of 3,3-disubstituted indolines from readily available aryl iodides. The reaction exhibits broad functional group tolerance, and its utility is exemplified in a streamlined formal synthesis of a rhodamine dye. Preliminary results of the asymmetric version of this reaction have also been obtained.