in tetrahydrofuran byproducts: KCl; operations carried out under moisture-free conditions; soln. of Me3SnCl in anhydrous THF added dropwise to a susp. of potassium phthalimide in THF; stirred at ambient temp. under nitrogen for 8 h; KCl filtered off; solvent evaporated in vacuo; residue purified by vacuum sublimation; elem. anal.;