[2-(methoxymethyl)-6-(trifluoromethyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl]methanol a3 (3.26 g, 0.122 mol, 1 eq) and p-toluenesulphonic acid (2.10 g, 0.122 mol, 1 eq) are successively added to a solution of 4-(3,3,3-trifluoropropyl)imidazolidin-2-one a10 (2.22 g, 0.122 mol, 1 eq) in toluene (450 ml). The mixture is heated at 110° C. overnight. The reaction is not complete and another portion of intermediate a10 (1 g, 5.49 mmol, 0.45 eq) is added. The mixture is heated at 110° C. overnight, then the solvent is evaporated under reduced pressure. Water is added to the residue, the mixture is extracted with CH2Cl2, the organic layer is dried over MgSO4, filtered and condensed under reduced pressure. The residue is purified by chromatography over silicagel (eluent: CH2Cl2/MeOH/NH4OH 98/2/0.2) to afford 336 mg of 1-{[2-(methoxymethyl)-6-(trifluoromethyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl]methyl}-4-(3,3,3-trifluoropropyl)imidazolidin-2-one 5 as a yellow oil.
