Regioselective cycloaddition of 3-azatrienes with enamines. Synthesis of pyridines derived from β-aminoacids

Abstract Aza-Wittig reaction of N -vinylic phosphazenes with α,β-unsaturated aldehydes leads to the formation of 3-azatrienes through a [2+2]-cycloaddition–cycloreversion process. Subsequent, regioselective [4+2]-cycloaddition of 3-azatrienes with pyrrolidinocycloalkanone affords bicyclic dihydropyridines and pyridines in a regioselective fashion. 2-Heterodiene moiety of azatriene is involved in the formation of the six-membered ring skeleton of pyridine derivatives.