Daniel Gryko

Recently we have discovered and optimized the first practical synthesis of non-fused pyrrole[3,2-b]pyrroles via domino reaction of aldehydes, primary amines, and butane-2,3-dione.¹ Six bonds are formed in heretofore unknown tandem process, which gives rise to substituted pyrrole[3,2-b]pyrroles – the ‘missing link’ on the map of aromatic heterocycles. Unparalleled simplicity and versatility of this one-pot reaction, non-chromatographic purification and superb optical properties (including strong violet, blue or green fluorescence both in solution as well as in the solid state), brought these molecules from virtual non-existence to the intensively investigated area functional π-systems. The parent 1,4-dihydro-pyrrolo[3,2-b]pyrroles served as building block to construct various π-expanded analogs including nitrogen-embedded buckybowl with inverse Stone–Thrower–Wales topology² and diindolo[2,3-b:2‘,3‘–f]pyrrolo[3,2-b]pyrroles. These compounds constitute the most electron-rich ladder-type heteroacenes known to date – E_HOMO was located at ca. −4.6 eV. Strongly fluorescent diindolo[2,3-b:2‘,3‘–f]pyrrolo[3,2-b]pyrroles represent the only existing compounds bearing the pyrrolo[3,2-b]pyrrolo[2′,3′:4,5]pyrrolo[2,3-d]pyrrole core.

References:

1. Krzeszewski, M.; Gryko, D.; Gryko, D. T. Acc. Chem. Res., 2017, 50, 2334.
2. Mishra, S.; Krzeszewski, M.; Pignedoli, C. A.; Ruffieux, P.; Fasel, R.; Gryko, D. T. ‘, Nature Commun. 2018, 1714.

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Wed. April 3 | 11:25 am-11:50 am – Pyrrolo[3,2-b]pyrroles – Electron-rich Functional Heterocycles