The reaction of isobutylene hydroalcoxycarbonylation with CO and polyhydric alcohols (ethylene glycol, glycerol) in the presence of the catalytic system Pd(aacac)(2)-PPh3-TsOH has been investigated. It was found that carbonylation of isobutylene with CO in the presence of ethylene glycol yields a mixture of mono-and diglycol esters of isovaleric acid, irrespective of the initial reactant ratio. During the hydroalcoxycarbonylation of isobutylene with glycerol, either mono- and di- or mono-, di-, and triglycerides of isovaleric acid are formed depending on the reactant ratio.