Regioselective preparation of 6-allyl-7-hydroxycoumarin from 7-allyloxycoumarin via boron halide catalysed ortho-Claisen rearrangement of 4′-allyloxycoumaric acid derivatives

An efficient synthesis of 6-allyl-7-hydroxycoumarin, a key intermediate for the preparation of linear coumarins, is described via a regioselective catalysed ortho-Claisen rearrangement of methyl 4′-allyloxy-2′-methoxycinnamate.