A stereocontrolled hetero‐Diels–Alder reaction of enantiomeric Ellman's fluoral aldimine with Danishefsky's diene affords diastereomerically pure N ‐sulfinyl‐protected 6‐trifluoromethyltetrahydropyridone. In addition, a highly diastereoselective, catalyst‐free aza ‐Mukaiyama addition of Rawal's diene to the CN bond of enantiomeric fluorine‐containing aldimines, R F CHNS(O) tert ‐Bu (R F = CF 3 , CHF 2 , CF 2 Me, CF 2 Ph), has been developed, providing diastereomerically pure enaminones. These chemically and configurationally stable enaminones are cleanly converted under acidic conditions into enantiomeric tetrahydropyridones bearing a chiral fluoroalkylated amino fragment at the 6‐position. Furthermore, cyclocondensation of the enaminones with hydrazines affords the corresponding pyrazoles incorporating a stereochemically pure fluoroalkylated amino group.
Rassukana et al. (Fri,) studied this question.