Synthesis, Structure, and Fluorescence of Isomeric Indolizinediones. Carbonyl-Bridged Isodipyrrinones

Summary.

In “one-pot” reactions, pyrrole-α- and β-aldehydes condense readily with 4-ethyl-3-methyl-3-pyrrolin-2-one to give isodipyrrinone analogs, which undergo intramolecular cyclization when the pyrrolealdehyde possesses an α or β-CO₂R group. The resulting regioisomeric pyrroloindolizinediones, with structures confirmed by NMR analysis, exhibit strong fluorescence, with quantum yields (φ_F) as high as 0.91 at λ_em∼450–550 nm.