Cinchona-Based Primary Amine Catalyzed a Proximal Functionalization of Dienamines: Asymmetric α‑Fluorination of α‑Branched Enals

Fluorination of dienamines generated
by α-branched enals
and 6′-hydroxy-9-amino-9-deoxy-epi-quinidine
(30 mol %) with NSFI show excellent α-regioselectivity to construct
allylic fluorides containing a highly stereocontrolled quaternary
fluorinated carbon (E/Z ≥
20/1 and up to 93% enantiometric excess (ee)). By
DFT calculation, the quinuclidine moiety of the catalyst was shown
to function as a coordinating group to promote a reaction at the proximal
α-position, and the nonclassical CH hydrogen bond plays an important
role in the high enantioselectivity.