A nucleophilic substitution reaction on optionally substituted dihalobenzenes is carried out in the presence of an optional catalyst followed by formation of and subsequent carboxylation of a Grignard reaction intermediate. In particular the present invention provides a process leading to optionally substituted hydroxybenzoic, alkanoyloxybenzoic, formyloxybenzoic and alkoxybenzoic acids from 1-substituted 2,6-dihalobenzenes. The invention also provides a process for the direct formation of an acyl chloride from a Grignard reagent by quenching with phosgene.