Understanding the fate of the oxyallyl cation following Nazarov electrocyclization: sequential Wagner-Meerwein migrations and the synthesis of spirocyclic cyclopentenones.

ABSTRACT: A general reaction sequence is described that involves Nazarov cyclization followed by two sequential Wagner-Meerwein migrations, to afford spirocyclic compounds from divinyl ketones in the presence of 1 equiv of copper(II) complexes. A detailed investigation of this sequence is described including a study of substrate scope and limitations. It was found that after 4π electrocyclization, two different pathways are available to the oxyallyl cation intermediate: elimination of a proton can give the usual Nazarov cycloadduct, or ring contraction can give an alternative tertiary carbocation. After ring contraction, either [1,2]-hydride or carbon migration can occur, depending upon the substitution pattern of the substrate, to furnish spirocyclic products. The rearrangement pathway is favored o

SUBMITTER: Huang J 

PROVIDER: S-EPMC3104681 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature