Development of a Nazarov Cyclization/Wagner−Meerwein Rearrangement Sequence for the Stereoselective Synthesis of Spirocycles

A stereoselective Nazarov cyclization/Wagner−Meerwein rearrangement sequence for the synthesis of spirocyclic compounds was developed and the efficiency was found to be dependent upon both the type and the amount of promoter used to generate the intermediate oxyallyl cation.

Abstract

A stereoselective Nazarov cyclization/Wagner−Meerwein rearrangement sequence for the synthesis of spirocyclic compounds was developed. While a range of different substrate types engaged in the cyclization/rearrangement sequence, it was found that different substrates underwent different reaction pathways. Depending on the substitution pattern of the substrate, the sequence was terminated by either a hydride shift or the shift of a vinyl or aryl group. It was also possible to install adjacent quaternary stereocenters using this protocol. The efficiency of the Wagner−Meerwein rearrangement was found to be dependent upon both the type and the amount of promoter used to generate the intermediate oxyallyl cation.