Migratory Selectivity in the Ring Expansion of α,β-Unsaturated Cyclic Ketones via β-Hydroxy Selenides

Article abstract of DOI:10.1021/jo00225a043

α-Phenylseleno alcohols, available by the direct condensation of α-phenylselenyl anions with α,β-unsaturated ketones, are efficiently transformed to ring-expanded enones upon reaction with thallium ethoxide in chloroform.Ten examples have been studied for the purpose of evaluating the relative migratory capabilities of the α-vinyl and α'-alkyl groups in a variety of structural contexts.When the conformationally unconstrained substrate 8 is concerned, exclusive vinyl migration was observed.In more rigid starting materials, the interrelationships of steric and conformational influences associated with proper antiperiplanar alignment of the PhSeCCl2H leaving group take on considerable importance.The presence of additional double bonds in the reactant does not introduce a serious problem associated with unwanted reaction with the dichlorocarbene intermediate.These various issues are discussed in light of the synthetic potential of the process.