Versatile Synthesis of 2,2-Disubstituted Indolinones via Protected Indolones Generated by One-Pot Multi-oxidation of 2-Substituted Indoles

The discovery of expeditious multi-oxidation of indoles to masked indolones led us to the development of a versatile synthetic method to access a variety of 2,2-disubstituted indolinones bearing two different substituents.Oxidation of 2,3-disubstituted indole followed by alkyl group migration is a well-known method to obtain indolin-3-one, i.e., indoxyl. 1 The migration step is stereospecific in terms of the stereochemistry of the initial oxidation and, in addition, it should be noted that it is usually successful in the case of ring contraction reaction to form spiro-indolin-3-one (spiro-indoxyl).