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Updated: Jul 2, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Converting 9-Methyldipyrrinones to 9-H and 9-CHO Dipyrrinones
Stefan E Boiadjiev1, David A Lightner
1Chemistry Department, University of Nevada, Reno, NV 89557-0020 USA.
Abstract:
Yellow 9-methyldipyrrinones can be converted readily and in high yields to symmetric linear tetrapyrroles, blue biliverdinoids, which are cleaved in half, smoothly at room temperature to afford yellow 9-H dipyrrinones, and 9-CHO dipyrrinones as their violet to orange colored adducts with the carbon acid used for the scission: thiobarbituric acid (TBA), N,N'-diethylthiobarbituric acid, barbituric acid, N,N'-dimethylbarbituric acid and Meldrum's acid. The adducts, usually only of passing interest, are formally Knövenagel condensation products of a 9-CHO dipyrrinone with TBA and other carbon acids of this work, and a reverse Knövenagel reaction of such adducts leads to 9-CHO dipyrrinones. Under a set of improved reaction conditions the sequence thus efficiently converts 9-CH(3) dipyrrinones to 9-H and 9-CHO dipyrrinones.
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