The Steglich Rearrangement of 2-Oxindole Derivatives Promoted by Anion-based Nucleophilic Catalysis

The first small anion-triggered Steglich rearrangements are reported. Tetrabutylammonium carboxylates-, cyanide- and fluoride promote the O- to C-acyl transfer of a range of O-acylated oxindoles to form 3,3-disubstituted oxindole products with new quaternary stereocentres. DFT calculations on the TBAF-mediated reaction strongly support a nucleophilic catalysis mechanism involving initial attack of fluoride on the O-acyl group to give an enolate and an acyl fluoride in the rate determining step.