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

1. A process for the direct preparation of a 1,4-diketopyrrolo[3,4-c]pyrrole of the formula

wherein R 1 and R 2 independently of each other are an unsubstituted or substituted isocyclic or heterocyclic aromatic radical, which process comprises

(a) heating an appropriate molar ratio of a disuccinate with a nitrile of the formula (II)

R 1 —CN  (II)

or of the formula (III)

R 2 —CN  (III)

or with mixtures of said nitriles, in an organic solvent and in the presence of a strong base, to form an intermediate condensation product,

(b) conditioning of the intermediate condensation product obtained in step (a) in water or a mixture of water and a water-miscible solvent, optionally in the presence of an inorganic acid, to form the compund of formula (I) and

(c) optionally conditioning of the product obtained in step (b) in an aprotic solvent, characterized in that a nitrile compound of the formula

wherein R 40 , R 41 and R 42 are independently of each other hydrogen, linear or branched C 1-10 -alkyl, C 1-10 -alkoxy or C 1-10 -thioalkyl, C 5-10 -cycloalkyl, C 6-10 -aryloxy, C 6-10 arylthio, C 7-10 -aralkyloxy, C 7-10 -aralkylthio, halogen, CN, CONR 5 R 6 , C(O)OR 7 or SO 2 R 9 ; is added at the beginning of the synthesis, wherein a particle growth regulator of the formula

is obtained, wherein R 1 , R 2 , R 40 , R 41 and R 42 are ad defined above, or a particle growth regulator is added in the heating step (a), the conditioning step (b) or (c),

wherein said particle growth regulator is a compound of the formula

wherein X is O, S or NR 14 , wherein R 14 is linear or branched C 1-10 -alkyl, C 7-10 -aralkyl or C 6-10 -aryl;

R 12 and R 13 are independently of each other hydrogen, linear or branched C 1-10 -alkyl,

C 1-10 -alkoxy or C 1-10 -thioalkyl, C 5-10 -cycloalkyl, C 6-10- -aryloxy, C 6-10 -arylthio, C 7-10 -aralkyloxy,

C 7-10 -aralkylthio, halogen, CN, CONR 5 R 6 , C(O)OR 7 , SO 2 R 9 ; or a compound of the formula

wherein R 15 and R 16 are independently of each other hydrogen, linear or branched C 1-10 -alkyl,

C 1-10 -alkoxy, or C 1-10 -thioalkyl, C 5-10 -cycloalkyl, C 6-10 -aryloxy, C 6-10 arylthio, C 7-10 -aralkyloxy,

C 7-10 -aralkylthio, halogen, CN, CONR 5 R 6 , C(O)OR 7 , SO 2 R 9 , wherein

R 5 and R 6 are hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl or C 6-10 -aryl,

R 7 is hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl, C 7-10 -aralkyl or C 6-10 -aryl,

R 9 is hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl, C 7-10 -aralkyl, C 6-10 -aryl or NR 10 R 11 ,

wherein

R 10 and R 11 are hydrogen, linear or branched C 1-10 -alkyl, C 1-10 -alkyl, C 7-10 -aralkyl or C 6-10 -aryl.

2. Process according to claim 1 , wherein 0.1 to 20.0% of the nitrile compound of formula IV is added at the beginning of step (a).

3. Process according to claim 1 , wherein 0.1 to 20.0% of the DPP compound of formula V or VI is added at the beginning or the end of step (a).

4. Process according to claim 2 , wherein the product of step (a) is conditioned in water containing 0 to 100% of a water-miscible solvent, wherein the water-miscible solvent is selected from the group consisting of alcohols, polyols, nitriles, organic acids, amides, esters, ethers, ketones, amines and a mixture of these solvents.

5. Process according to claim 4 , wherein the conditioning step (b) is done in the presence of 1 to 99% of an inorganic acid.

6. Process according to claim 5 , wherein the product obtained in conditioning step (b) is then conditioned i an aprotic, water-miscible solvent in the presence of 0 to 99%, water, or in a nonmiscible solvent with a high boiling point.

7. Process according to claim 1 , wherein the product of step (a) is conditioned in water containing 0 to 100% of a water-miscible solvent, wherein the water-miscible solvent is selected from the group consisting of alcohols, polyols, nitriles, organic acids, amides, esters, ethers, ketones, amines and a mixture of these solvents.

8. Process according to claim 7 , wherein the conditioning step (b) is done in the presence of 1 to 99% of an inorganic acid.

9. Process according to claim 8 , wherein the product obtained in conditioning step (b) is then conditioned in an aprotic, water-miscible solvent in the presence of 0 to 99% water or in a non-miscible solvent with a high boiling and 0.1 to 20.0% of the DPP compound of formula V or VI.

10. A process according to claim 1 , wherein the nitrile of formula (II) or of formula (III) is of the formula

wherein R 20 , R 21 and R 22 independently of each another are hydrogen, fluorine, chlorine, bromine, carbamoyl, cyano, trifluoromethyl, C 2-10 -alkylcarbamoyl, C 1-10 -alkyl, C 1-10 -alkoxy, C 1-10 -alkylmercapto, C 2-10 -alkoxycarbonyl, C 2-10 -alkanoylamino, C 1-10 -monoalkylamino, C 1-20 -dialkylamino, phenyl or phenoxy, phenylercapto, phenoxycarbonyl, phenylcarbamoyl or benzoylamino, each unsubstituted or substituted by halogen, C 1-4 -alkyl or C 1-4 -alkoxy, with the proviso that at least one of R 20 , R 21 is hydrogen.

11. A DPP derivative of the formula V

wherein X is O or S, wherein R 14 is linear or branched C 1-10 -alkyl, C 7-10 -aralkyl or C 6-10 -aryl; R 12 and R 13 are independently from each other hydrogen, linear or branched C 1-10 -alkyl, C 1-10 -alkoxy or C 1-10 -thioalkyl, C 5-10 -cycloalkyl, C 6-10 aryloxy, C 6-10 -arylthio, C 7-10 aralkyloxy, C 7-10 -aralkylthio, halogen, CN, CONR 5 R 6 , C(O)OR 7 or SO 2 R 9 ; wherein R 5 and R 6 are hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl or C 6-10 -aryl, R 7 is hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl or C 6-10 -aryl, R 9 is hydrogen, linear or branched C 1-10 -alkyl, C 5-10 -cycloalkyl, C 7-10 -aralkyl, C 6-10 -aryl or NR 10 R 11 , wherein R 10 and R 11 are hydrogen, linear or branched C 1-10 -alkyl, C 7-10 -aralkyl or C 6-10 -aryl, with the proviso that 3,5,6-triphenyl-1H-furo[3,4-c]pyrrole- 1,4-(5H)-dione is excluded.

12. A process according to claim 9 wherein the water-miscible solvent is N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl formamaide, or N,N-dimethylacetamide.

13. Process according to claim 8 wherein the inorganic acid is hydrochloric, sulfuric or phosphoric acid.