Process for the preparation of pyrrolo[3,4-c]pyrroles, and novel pyrrolo[3,4-c]pyrroles

摘要

The invention relates to a process for the preparation of pyrrolo[3,4-c]pyrroles of formula (1) <IMAGE> (1) wherein each of R1 and R2 independently of the other is an alkyl or aralkyl group or an isocyclic or heterocyclic aromatic radical, which process comprises reacting an ester of formula (2) or (3) <IMAGE> with a nitrile of the formula R2CN, in which formulae each of R and R' independently of the other is an alkyl or aryl group, and R1 and R2 are as defined above, in the presence of a strong base in an organic solvent. The invention also relates to compounds of formula (8) <IMAGE> (8) wherein R3 in an alkyl or aralkyl group or an ortho-substituted isocyclic or heterocyclic aromatic radical and R4 is an alkyl or aralkyl group or an isocyclic or heterocyclic aromatic radical. The pyrrolopyrroles obtained are valuable pigments for coloring compounds of high molecular weight such as plastics and lacquers in yellow to red shades of excellent fastness properties.