Indole, 3-chloro-, oxindole from

Grant and Krische have described a racemic protocol for the synthesis of allcarbon C3 quaternary centers from 3-hydroxy-3-tert-prenyloxindole 76 that was accessed via ruthenium catalyzed addition of 1,1-dimethylallene 75 to isatin 74 [45]. As outlined in Scheme 21, 76 was converted to the electrophilic 3-chloro derivative, which was trapped with indole under basic conditions to afford 78 in 60% yield. A mechanism has been proposed for the C-C bond-forming event that involved first-order irmizatirHi of chloride irm assisted by delocaUzatiOTi of oxindole... 

The authors have found that nitronates 11 are derived from intramolecular nucleophilic displacement of the chloro atom with oxygen of the nitro group (Scheme 9). Moreover, the intramolecular VNS reactions of nitroarenes proved to be a successful procedure for the synthesis of various indole derivatives. For instance, cyclization of 3-nitrochloroacetanilide 12 caused by action of f-BuOK affords N-substituted oxindole 13, which is hardly accessible by other methods [28] (Scheme 10). 

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