Stereoselective synthesis of spirocyclic oxindoles based on a one-pot Ullmann coupling/Claisen rearrangement and its application to the synthesis of a hexahydropyrrolo[2,3-b]indole alkaloid
An efficient and convenient approach to the synthesis of spirocyclic oxindoles from iodoindoles has been developed. The most striking feature of this approach is that the sequential intramolecular Ullmann coupling and Claisen rearrangement proceeds in a one-pot manner to afford 3-spiro-2-oxindoles in good yield with excellent diastereoselectivity. Application of this one-pot reaction to chiral non-racemic tertiary alcohol substrates resulted in complete chirality transfer to the spirocyclic quaternary carbon. Using this method, asymmetric total synthesis of (-)-debromoflustramine B was accomplished.
Highly diastereoselective one-pot synthesis of spirocyclic oxindoles through intramolecular Ullmann coupling and Claisen rearrangement
(Chemical Equation Presented) An efficient and convenient approach to the synthesis of spirocyclic oxindoles from iodoindoles involves a sequential intramolecular C-O Ullmann coupling reaction and Claisen rearrangement (see scheme). The one-pot procedure affords 3-spiro-2-oxindoles in good yield with excellent diastereoselectivities.