New Transformations from a 3-Silyloxy 2-Aza-1,3-diene: Consecutive Zr-Mediated Retro-Brook Rearrangement and Reactions with Electrophiles

A one-pot procedure for the transformation of the title compound to α-functionalized (silylated) and α,β-unsaturated secondary amides was described. The following steps were involved: a Zr-mediated retro-Brook rearrangement, selective deprotonation with n-BuLi on the organometallic intermediate, and trapping with electrophiles including alkyl and acyl halides and aldehydes. The electrophilic addition step occurred at a stabilized α-silyl carbanion center without affecting the near transition metal residue. In the case of aldehydes, the Peterson alkenation reaction took place on the transition metal complex in a highly stereoselective way.