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.