Ohmic heating assisted synthesis of coumarinyl porphyrin derivatives

Ohmic heating offers a very efficient way of performing organic reactions using water as solvent. An efficient access to new coumarinyl porphyrin derivatives bearing pyrano[3,2-c]coumarin motifs at the β-pyrrolic position of porphyrin macrocycles is disclosed by using this type of heating. The synthetic strategy involved a sequential Knoevenagel and hetero-Diels-Alder reaction between 2-vinyl-5,10,15,20-tetraphenylporphyrinatozinc(ii) and α-methylenechromane derivatives generated in situ from 4-hydroxycoumarin and aromatic aldehydes in aqueous media. The results obtained under ohmic heating were compared with those obtained under conventional heating using water and also organic solvents.