Synthetic studies related to diketopyrrolopyrrole (DPP) pigments. Part 2: The use of esters in place of nitriles in standard DPP syntheses: Claisen-type acylations and furopyrrole intermediates |
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| Authors: | Colin JH Morton Richard L Riggs Nicholas J Westwood Alexandra MZ Slawin |
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| Institution: | a School of Chemistry, University of St. Andrews, Purdie Building, St. Andrews, Fife KY16 9ST, Scotland, UK
b Ciba Specialty Chemicals Inc., PO Box, CH-4002 Basel, Switzerland |
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| Abstract: | Ethyl 2-aryl-4,5-dihydro-5-oxopyrrole-3-carboxylates react with esters or acyl halides in the presence of a strong base to give 4-acyl derivatives, which exist predominantly as either E- or Z-enols. These are cyclised, either in solution at temperatures >200 °C or by microwave irradiation, to 3,6-disubstituted 1H-furo3,4-c]pyrrolediones which, after N-protection, are convertible by reaction with primary amines into novel N,N′-disubstituted DPP derivatives. |
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| Keywords: | Acylation Cyclisation Microwaves Pigments Pyrrolinones |
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