The present invention provides a process from preparing isocoumarin-3-yl derivatives comprising reacting a homophthalic anhydride derivative with a carbonyl compound, wherein the carbonyl group is substituted with an acyl activating group, in the presence of a reaction medium comprising a solvent and a base. The invention also encompasses a process for the preparation of homophthalate esters useful in the preparation of homophthalic anhydride reactants as well as an integrated process wherein the twp reactions are carried out sequentially to afford the desired isocoumarin derivative.