Synthesis and Optical Properties of Tetraaryl‐1,4‐dihydropyrrolo[3,2‐b]pyrroles

A practical synthesis of nonfused 1,4‐dihydropyrrole[3,2‐b]pyrroles in a domino reaction of aldehydes, primary amines, and butane‐2,3‐dione has been discovered. Six bonds are formed in a tandem process, which gives rise to tetrasubstituted pyrrole[3,2‐b]pyrroles—the least studied among heteropentalenes. Unparalleled simplicity and versatility of this one‐pot reaction, no chromatography, as well as superb optical properties have the potential to make 1,4‐dihydropyrrole[3,2‐b]pyrroles the molecules of choice for various applications. As a proof of principle, cell uptake of selected dyes was demonstrated.