The chemistry of pyrrolic compounds. XLII. The synthesis of some diacetyldeuteroporphyrins as intermediates in the preparation of the isomeric protoporphyrins: a comparative spectroscopic study of the diacetyldeuteroporphyrins

A range of isomeric diacetyldeuteroporphyrins has been synthesized by the oxidative cyclization of appropriately substituted bilenes-b, and the electronic and n.m.r. spectra of these porphyrins have been studied. As a result it has been shown that the relative position of the two acetyl groups influences the absorption pattern of the visible spectrum more precisely than was previously appreciated. In consequence, it is possible to recognize the 1,4, 2,3 and 2,4 relative distribution of the acetyl groups by an examination of the electronic spectrum. In addition, it is clear that the acetyl groups present in this series of porphyrins affect the chemical shift of all the methine protons and not only the one which is directly adjacent to the carbonyl function.