. . . "The bis-azidophthalimidyl derivatives of the formula I can be prepared by reacting a compound of the formula XIII ##STR18## in which R is as defined under formula I and Q1 is a halogen atom, such as chlorine, fluorine or bromine, or, preferably, the nitro group, in an inert organic solvent at a temperature between about 30??? and 120??? C., especially between about 70??? and 100??? C., with an azi" .