Pt(II)- or Au(III)-Catalyzed [3+2] Cycloaddition of Metal-Containing Azomethine Ylides: Highly Efficient Synthesis of the Mitosene Skeleton

[reaction: see text] Only 1-3 mol % of PtCl(2) or AuBr(3) was sufficient to promote generation and [3+2] cycloaddition of transition-metal-containing azomethine ylides derived from N-(o-alkynylphenyl)imines bearing an internal alkyne moiety. A highly efficient method for the preparation of synthetically useful tricyclic indole derivatives having a substituent at the 3-position of the indole nucleus was established by this method.