New spirocyclic oxindole synthesis based on a hetero Claisen rearrangement

reaction: see text] A new method for preparing spirocyclic oxindoles is presented. Featuring a 3,3]-sigmatropic enolate rearrangement, the three-step process converts carboxylic acid starting materials to oxidnole products in overall yields of 52-76%. The enolate rearrangement step occurs at -78 degrees C and provides easy access to oxindole products that have previously been difficult to prepare.