NOVELTY - Preparing a 3-formylmethyl-benzoic acid derivative (II) comprises: (a) oxidizing a 3-allyl-benzoic acid derivative (III) with a suitable oxidizing agent in the presence or absence of a base, optionally in the presence of a phase transfer catalyst, to produce a 3-(2,3-dihydroxypropyl)-benzoic acid derivative (IV); and (b) reacting (IV) with a glycol cleavage agent to produce the 3-formylmethyl-benzoic acid derivative (II), and optionally purifying (II) using a suitable solvent or a mixture of suitable solvents.    USE - The process is useful for preparing (II) (claimed), which is useful as intermediates in the preparation of benzofurancarboxamide derivatives, preferably prucalopride having gastrointestinal motility stimulating properties.    ADVANTAGE - The improved process easily provides 3-formylmethyl-benzoic acid derivative with high yield and purity in an environmentally friendly and industrial manner.    DETAILED DESCRIPTION - Preparing 3-formylmethyl-benzoic acid derivative of formula (II) or its salt, comprises: either (a) oxidizing a 3-allyl-benzoic acid derivative of formula (III) or its salt with a suitable oxidizing agent in the presence or absence of a base, optionally in the presence of a phase transfer catalyst, to produce a 3-(2,3-dihydroxypropyl)-benzoic acid derivative of formula (IV), and (b) reacting (IV) with a glycol cleavage agent to produce the 3-formylmethyl-benzoic acid derivative of formula (II) or its salt, and optionally purifying (II) using a suitable solvent or a mixture of suitable solvents; or the step of (b) as above per se.    R = H or alkyl;    R1 = H or nitrogen protecting group P;    R2 = H or halo; and    R3 = H, or alkali or alkaline earth metal ion.    INDEPENDENT CLAIMS are included for:    (1) preparing (IV) comprising oxidizing (III) with a suitable oxidizing agent in the presence or absence of a base, optionally in the presence of a phase transfer catalyst, to produce (IV) or its salt, and optionally purifying (IV) using a suitable solvent or a mixture of suitable solvents; and    (2) the compound (IV).