Regioselective Conjugate Addition of Nitriles to ,-Unsaturated Imines: Synthesis of Fluorinated Primary Enamines and 2-Aminopyridine Derivatives

The regioselective Michael addition of the carbanion of 2-phenylacetonitrile (R-2 = Ph) and malononitrile (R-2 = CN) to fluoroalkylated ,-unsaturated imines 1 is described. Fluorinated imines 1 were used as intermediates for the regioselective 1,4-addition and synthesis of functionalized fluorinated primary enamines 5 and 7, fluorine-containing trans-3,4-dihydro-2-aminopyridines 2, and fluorinated 2-aminopyridines 4 and 8, which were obtained with total atom economy. Derivatives 2 and 8 were also prepared by an intramolecular cyclocondensation reaction of functionalized fluorinated primary enamines 5 and 7, respectively, in the presence of a base (NaH).