Synthesis of Benzopyran–Phenylpropanoid Hybrids via Matsuda–Heck-Arylation and Allylic Oxidation

The synthesis of
coumarin– and flavonoid–chalcone
hybrids via Pd-catalyzed Heck-type coupling of arene diazonium salts
and 8-allylcoumarins and −flavonoids is reported. The β-hydride
elimination step proceeds with high regioselectivity if an OMOM-substituent
is present at the position C7, adjacent to the allyl group. A selective
allylic oxidation of the coupling products was accomplished using
DDQ in the presence of silica to furnish the chalcones.