Regioselective Synthesis of Chrom-4-ones and Fused Flavones

Significance

Whereas treatment of the α-cyano acetophenone 1 with aromatic aldehydes under Et₃N/MeOH conditions leads to the expected Knoevenagel-Michael addition products iso­flavones A and B. Change of solvent to toluene ­results in the polycondensation products X in modest to very good yields. Alternatively, the ­cyanoflavanones A and B can be converted into the condensed flavones X under the same conditions thus establishing precursor/product relationships. The substrate scope was reasonably well studied. Compounds B show intense fluorescent properties with high quantum yields in the range of 0.82-0.87.