Abstract 5, 7-Dichlorocoumaran-3-one has been prepared from methyl 2-hydroxy-3, 5- dichlorobenzoate by a three stage synthesis. It could not be prepared by (i) intramolecular cyclization of 2, 4-dichlorophenoxy-acetic acid or 2, 4-dichlorophenoxyacetyl chloride or (ii) by the reaction of ω-bromo-2-hydroxy-3, 5-dichloroacetophenone with bases. The reaction of 2, 4-dichlorophenoxyacetic acid with phosphorus pentoxide in benzene gave 2, 4- ...
