Synthesis of Enantioenriched Fluorinated Enol Silanes Enabled by Asymmetric Reductive Coupling of Fluoroalkylacylsilanes and 1,3-Enynes and Brook Rearrangement

Fluorinated
enol silanes are broadly useful in various synthetic
transformations such as Mukaiyama aldol, Michael, and Mannich reactions.
However, previous methods to these intermediates are limited to racemic
synthesis. Therefore, the development of access to enantioenriched
ones is of great value. We now describe an enantioselective reductive
coupling reaction of fluoroalkylacylsilanes and 1,3-enynes. The coupling
products were easily transformed to fluorinated enol silanes with
the retention of enantiopurity though Brook rearrangement. The practicality
of our methodology was demonstrated by the multisteps-one-isolation
processes for the synthesis of alkynyl, alkenyl, and alkyl substituted
enantioenriched β,β-difluoro enol silanes. The applications
of the enantiopure β,β-difluoro enol silane in the synthesis
of valuable chiral organofluorine compounds demonstrated the synthetic
potential of our reaction.