PtCl₂‑Catalyzed Cycloisomerization of 1,8-Enynes: Synthesis of Tetrahydropyridine Species

The cycloisomerization of 1,8-enynes in the presence of platinum­(II) chloride was developed to generate bicyclic nitrogen-containing heterocycle species via 6-endo-dig cyclization and [3,3]-sigmatropic rearrangement in acceptable to good yields. The related control experiments and preliminary mechanistic studies indicate a plausible mechanism involving 1,6-endo-dig aminoplatination of the alkyne and allylic [3,3]-sigmatropic rearrangement with total inversion of the allylic moiety