Unexpected formation of porphyrinic enyne under Sonogashira conditions

Reaction of 5-iodo-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrin with excess trimethylsilylacetylene under Sonogashira conditions gives an unexpected porphyrinic enyne suitable for further transformations. The NMR spectrum and structural analysis of the porphyrin enynes show that the substituent on the acetylene group is positioned above the porphyrin ring. This structural characteristic makes the microenvironment of the porphyrin center in a controllable fashion.