Diketo-pyrrolopyrroles

Furo[3,4-c]pyrrolediones are important intermediates in the synthesis of diketo-pyrrolopyrrole (DPP) pigments. Smith and coworkers have described the preparation of several different 3,6-diaryl-substituted furo[3,4-c]pyrrole-l,4-diones by microwave-assisted cyclization of readily available 4-aroyl-4,5-dihydro-5-oxo-2-arylpyrrole-3-carboxylates (Scheme 6.192) [353]. While conventional heating in Dowtherm A at 230-240 °C for 64 h provided only moderate product yields, microwave irradiation of the neat starting material at 250 °C for 10 min provided significantly increased yields. 

These studies were followed up by Ciba-Geigy and systematically developed into a synthetic route to a group of very fast red pigments, known as diketo-pyrrolopyrrole pigments (DPP pigments) [3, 4], since the brilliant red crystals of 141 turned out to be extremely insoluble. 

Figure 2.26 Synthetic route to the diketo-pyrrolopyrrole red pigment Cl Pigment Red 254.

J.C. Bijleveld, et al. Efficient solar cells based on an easily accessible diketo-pyrrolopyrrole polymer. Advanced Energy Materials, 2010.22 p. E242-E246. 

Figure 20-8 shows the crystal structure of a thiazine indigo compared to a diketo-pyrrolopyrrole with very similar molecular size, shape and particularly intermolecu-lar hydrogen bondings, which are mainly responsible for their pigmentary character such as insolubility, heat stability and exposure durability. 

Hao, Z., Schloeder, I. and Iqbal, A. (1999a). l,4-Diketo-3,6-bis-4-chloro-phenyl-pyrrolopyrrole in /3-modification—useful as pigment with more yellow-red nuance than Q -modification is. Prepd. by acid hydrolysis of soluble carbamate. Derivation and preparation by cooling. Ciba-Geigy Ltd. EP 690058 Al. [271]... 

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