Schiff bases (3a-d and 4a-c), synthesized from benzenedicarbaldehydes (terephthalaldehyde and isophthalaldehyde) and primary amines (methylamine, ethylamine, butylamine, and aniline), were carbonylated in the presence of CO~(CO)~ under an elevated pressure at 200-290" C to give dicarbonylated products, benzodipyrrolediones (Sa- d, loa-c, and l la-c), in high yields. 1, 2, 3, 4-Benzenetetracarboxylic acid (prehnitic acid) ...
![2,3,7,8-tetrahydro-2,7-diethylbenzo[1,2-c:3,4-c']dipyrrole-1,6-dione Structure](https://image.chemsrc.com/caspic/165/85068-01-5.png)
