PROPENTDYOPENTS [5-(2-OXO-2H-PYRROL-5-YLMETHYLENE)PYRROL-2(5H)-ONES] AND RELATED-COMPOUNDS .1. ON THE STRUCTURE OF THE PROPENTDYOPENT-ALKANOL ADDUCTS

The history of the propentdyopent problem is briefly summarized. Tetraethyl(methanol) propentdyopent and tetraethyl(water) propentdyopent are prepared from octaethylhaemin and from 3,3'', 4,4''-tetraethyl 2,2''-methylenedipyrrole-5-5''-dicarboxylic acid under specified oxidative conditions, are interconverted under appropriate acidic conditions, and readily form the orange zinc (II) complex of tetraethylpropentdyopent. Arguments are advanced to show that the water and methanol derivatives are to be formulated as the valley adducts (18a, b) of tetraethylpropentdyopent.