Study of the Hetero-[4+2]-Cycloaddition Reaction of Aldimines and Alkynes. Synthesis of 1,5-Naphthyridine and Isoindolone Derivatives

Both
experimental and computational studies for the cycloaddition
reaction between N-(3-pyridyl)­aldimines and
acetylenes where 1,5-naphthyridines are obtained are reported. The
reaction of benzaldimine with a methoxycarbonyl group in position
2 with phenyl acetylene, styrene, and indene afforded polycyclic isoindolone
derivatives. The mechanism of reaction of N-(3-pyridyl)­aldimines
with olefins can be explained by an asynchronous [4+2] cycloaddition;
in the case of acetylenes, the obtained results suggest a stepwise
mechanism through a 3-azatriene.