The Chemistry of Pyrrolic Compounds. LXI. Petroporphyrins From the Julia Creek Oil Shale: Further Evidence for the Derivation of Etiotype Petroporphyrins From Chlorophyll

Abstract

The synthesis of the porphyrins (2c-j) has been achieved by the oxidative cyclization of appropriately substituted biladienes-ac. The availability of authentic material has allowed the finalization of the structure of a series of aetiotype fossil porphyrins which vary in substitution pattern at positions 3 and 13. All combinations of H, Me and Et at these positions have now been isolated from natural sources. This points to a common precursor, possibly a divinylporphyrin, and strengthens the belief that the chlorophylls are the prime source of the petroporphyrins. A vinyl group, or a close derivative, is found at position 3 of all chlorophylls while fragmentation of the ubiquitous isocyclic ring of the chlorophylls could yield the vinyl group at position 13.