A novel approach for the synthesis of 5,5'-directly linked metal-free
bis-porphyrins is reported; McMurry type coupling of dipyrroketones (e
.g. 1) leads to 1,1,2,2-tetra(2-pyrrolyl)ethene 2, which after tetra-f
ormylation (to give 3) and MacDonald macrocyclization with a 1,9-di-un
substituted dihydrodipyrrin 4, affords the 5,5'-bis-porphyrin 5.