Preparation of unsaturated carboxylic acid esters

A transesterification process comprising reacting an unsaturated carboxylic acid ester of formula: H2C=C(R)-C(O)-OR' in which: R is hydrogen atom or a methyl radical, R' is a linear or branched alkyl radical having 1 to 3 carbon atoms, with an alcohol of formula: R''OH in which: R'' is an alkyl radical possessing a number of carbon atoms between 2 and 30 and greater than the abovementioned radical R', in the presence of at least one polymerization inhibitor, optionally at least one solvent and at least one transesterification catalyst which is a tetravalent chelate of zirconium corresponding to the following characteristics: ZrO2 content (in % by weight) : from 24 to 30, viscosity at 20 DEG C (in MPa.s) : 400-12,000, refractive index at 20 DEG C : 1.45-1.52, and in that the tetravalent chelate of zirconium is such that: at least one of these chelating groups is a (poly)-glycol ether, one or two of these chelating groups are acetylacetonategroups, the other chelating groups for attaining the valency IV of zirconium are alkoxy groups.