An Efficient Method for the Programmed Synthesis of Multifunctional Diketopyrrolopyrroles

A new, transformative methodology for the preparation of diketopyrrolopyrroles from aldehydes, primary amines, nitriles, and diethyl oxalacetate has been developed. It is now possible to prepare diketopyrrolopyrroles bearing an ordered arrangement of three different substituents from abundant and commercially available materials, allowing the independent regulation of all desired physicochemical properties. For the first time very electron-rich (carbazol-3-yl, dimethylaminophenyl, pyrrolo[3,2-b]pyrrolyl), and sterically hindered substituents (naphthalen-1-yl, quinolin-4-yl, acridin-9-yl, imidazo[1,5-a]pyridin-1-yl, 2-bromophenyl etc.) can be appended to the diketopyrrolopyrrole core by condensation of an appropriate nitrile with a pyrrolidin-2-one intermediate. Even greater synthetic possibilities are related to the fact that such demanding substituents as 4-dimethylaminophenyl, indol-3-yl, and 2-methoxyphenyl can be incorporated from aldehyde precursors, bypassing problems with the nitriles reactivity.