Diphosgene → 5-Isocyanato-2-(2,2,2-trifluoroethyl)-2-trifluoromethyl-1,3-benzodioxole

37 g of the product of Example 33 were dissolved in 50 ml of absolute 1,4-dioxane, and a solution of 13.5 g of diphosgene in 80 ml of absolute 1,4-dioxane was added. The mixture was then stirred for 6 hours at 110° C. (bath temperature), the solvent was then removed under vacuum and the remaining residue was subjected to fractional distillation under vacuum to give 18 g of product (=44% of theory) with a boiling point of 63° C. at 0.1 mbar. NMR: -59.3 and -85.0 ppm. 1H NMR: 3.0 ppm.