Synthesis of Fluorescent Pyrrolo[1,2-a]pyrimidines from Fischer Carbene Complexes as Building Blocks

A novel synthetic methodology is reported for the synthesis of fluorescent pyrrolo[1,2-a]pyrimidines. Fischer carbene complexes served as the synthetic platform for (3+3) cyclization to form the heterocyclic moiety. The reaction process furnished two products, their ratio being modulated by the metal, base, and solvent. The selectivity exhibited was studied by analyzing the potential energy surface with density functional theory tools. The photophysical properties of absorption and emission were also evaluated. The dyes absorbed at wavelengths of 240–440 nm, depending on the substituents. The maximum emission wavelength was in the range of 470–513 nm, with quantum yields of 0.36–1.0 and a high Stokes shift range of 75–226 nm.