PtCl2-catalyzed benzannulation of nickel(II) 2,3-dialkynylporphyrins to form unusual phenanthroporphyrins

Reaction of Ni(II) 2,3-dibromo-5,10,15,20-tetraphenylporphyrin with substituted stannyl alkynes generates substituted 2,3-dialkynylporphyrins in good yields. Thermolysis of these motifs with stoichiometric or even catalytic equivalents of PtCl2 yields unusual phenanthroporphyrins with only small amounts of the established picenoporphyrin or other side products.