In chemical industries, conversion of reaction solvents from organic solvents to water has been actively investigated for the purpose of cost reduction, safety, reduction of environmental loads and the like. However, there are only few examples of succeeding such conversion because of the problems of solubility of the reaction substrate or catalyst, safety and the like. In recent years, the inventors of the present invention succeeded in developing a Lewis acid catalyst which is stable even in water, and subsequently a Lewis acid catalyst integrated with a surfactant (see Patent Document 1), thereby greatly increased the possibility of carrying out synthesis reactions in water (see Non-Patent Document 1). Furthermore, the inventors of the present invention conducted investigation on the immobilization of a catalyst onto an insoluble support, for the purpose of facilitating the isolation of catalysts from products or the recovery/reuse of catalysts, and found that a Lewis acid catalyst which is bound to a hydrophobic polymer support and is stable in water, accelerates various reactions in water, compared with in an organic solvent (see Non-Patent Document 2, Patent Document 2 and Patent Document 3). Nevertheless, Lewis acid catalysts supported on organic polymers have problems such as that production of such catalysts is relatively difficult and expensive.