Evidence for a Fast (Major) and Slow (Minor) Pathway in the Schumm Devinylation Reaction of Vinyl Porphyrins
DiNello, R.K. and David DolphinH.
J. Org. Chem.
Devinylation of protohemin [Fe(III) protoporphyrin] to molten resorcinol proceeds via 2 pathways. Two of the 3 possible intermediates in the minor (slow) pathway were isolated and characterized as their di-Me esters. In both, C-alkylation of resorcinol occurred at the porphyrin C-1' vinyl side chains. These intermediates are, however, converted into deuterohemin far too slowly for them to be on the major pathway from protohemin to deuterohemin. Other intermediates, possibly in which O-alkylation of resorcinol occurred, are intermediates in the major (fast) pathway for this reaction.