Abstract Synthetic routes to o-carboxyphenyl derivatives of certain heterocyclic compounds, required for testing as plant growth regulators, were investigated. The preparation of 2-(5- phenyl-1, 3, 4-oxadiazol-2-yl) benzoic acid (3), 2-(5-phenyl-1, 3, 4-thiadiazol-2-yl) benzoic