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

A new general method for the synthesis of pyrrole-2,5-dicarbaldehyde and its 3-mono- and 3,4-disubstituted derivatives is reported. It involves the intermediate formation of the corresponding 2,5-bis(1,3-benzodithiol-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 of the corresponding dithiolic intermediate with further hydrolysis resulted in the formation of 1-methylpyrrole-2,5-dicarbaldehyde in 90% overall yield.