New 1-hetarylfuropyridines and chromenes based on pyridoxal and 4-hydroxycoumarin

Pyridoxal in the absence of catalyst forms furo[3,4-c]pyridine species (ortho aldehyde and hydroxymethyl groups are involved) which is further transformed into C–C hybrid with 4-hydroxycoumarin. Different products of chromeno-[3′,4′:5,6]pyrano[2,3-c]pyridine type are formed when pyridoxal hydrochloride or more sophisticated 2,4-dihydroxybenzaldehyde derivative are applied (herein, ortho aldehyde and hydroxy groups are involved into heterocyclization).