Structure and Mechanism Revision of a Catalyzed Cyclization of Benzaldehyde Bearing Alkyne-Nitrile

Pt­(II)-catalyzed
carbocyclization of benzaldehyde containing a
keto-nitrile functionality resulted in the formation, respectively,
of isochromenes and spiro-lactones instead of fused lactams and spiro-lactams
as was previously reported. The reaction mechanism was proposed, and
the products were identified by multidimensional NMR, IR, and X-ray
analysis. The structure of these new products was also confirmed by
their synthesis in an unambiguous manner using practical and short
approaches.