Kharasch-Type Cyclizations of 2-Substituted Indole Derivatives Surprisingly Lead to Spiroindoles

Starting from 1H-indole-2-carboxylic acid, a series of spiro[2-oxoindole-pyrrolidines] could be synthesized in a straightforward manner. The key reaction is a Kharasch radical cyclization reaction of trichloroacetylated precursors. The identity of the tricyclic final products that were formed could be determined as spiro[2-oxoindole-pyrrolidines] by using a combination of different analytical techniques [H-1, NMR, C-13 NMR, gHMBC, HRMS) and additional reactions. The produced skeletons are interesting from a medicinal point of view.