Scope and Limitations in the Use of α-Silyl and α-Stannyl Sulfones as Latent α-Sulfonyl Anions

Abstract

Three methods for the regeneration of α-sulfonyl anions from α-silyl sulfones and α-stannyl sulfones are investigated. These methods include: (1) treatment of α-silyl sulfones with electrophiles (aldehydes and acid halides) in the presence of fluoride ion; (2) reaction of α-silyl sulfones with n-butyllithium which produces an α-silyl anion via a migration of the -SiMe₃ group from the α-position to the ortho-position of the phenyl sulfones; and (3) direct transmetalation of α-stannyl sulfone by treatment with n-butyllithium. The addition of cerium [III] chloride is shown to substantially decrease enolization problems associated with addition of α-sulfonyl anions to carbonyl compounds bearing enolizable protons.