312 g (2.26 moles) of potassium carbonate, 11 g (0.066 moles) of potassium iodide and 11 g (0.034 moles) of tetrabutylammonium bromide are added to a solution of 222 g (0.655 moles) of 2-butyl-3-(4-hydroxybenzoyl)-5-nitro-benzofuran (formula (V)) in 1780 ml of DMF. The reaction mixture is heated to 50° C. and after approximately 30 minutes 100 g of 3-chloro-1-propanol are added dropwise. At the end of the dropwise addition, the reaction mixture is brought to 80-85° C. and left under stirring for 4-5 hours. Once the reaction is complete, the mixture is cooled to 40-50° C. and the inorganic salts are removed by filtering. The organic solvent is distilled at reduced pressure, maintaining the temperature around 60-70° C., and the residue is dissolved in 2220 ml of toluene. After performing three washing operations on the organic phase, each with 1130 ml of deionised water, the toluene is concentrated to residue. The crude product is dissolved with approximately 100 ml of ethyl acetate and the mixture is left under cooling at 0-4° C. for approximately 12 hours. The solid is filtered, the wet product is washed with a little ethyl acetate pre-cooled to 0-5° C. and it is dried under a vacuum at 40° C. for 6-7 hours. 181 g of 3-{4-[(2-butyl-5-nitro-1-benzofuran-3-yl)carbonyl]phenoxyl}propan-1-ol (formula (II)) are obtained.
