A CONVENIENT GENERAL-METHOD FOR THE SYNTHESIS OF PYRROLE-2,5-DICARBALDEHYDES

A new general method for the synthesis of pyrrole-2,5-dicarbaldehyde a nd its 3-mono- and 3,4-disubstituted derivatives is reported. It invol ves the intermediate formation of the corresponding 2,5-bis(1,3-benzod ithiol-2-yl)pyrroles followed by hydrolysis with HgO-35% aq. HBF4-DMSO . Pyrrole-2,5-dicarbaldehyde was obtained in overall yields of 43-65%, whilst that of the derivatives was 32-90%. Moreover the methylation o f the corresponding dithiolic intermediate with further hydrolysis res ulted in the formation of 1-methylpyrrole-2,5-dicarbaldehyde in 90% ov erall yield.