Treatment of N-alkyl-2-benzylseleno-N-trimethylsilylbenzamides, prepared from the N-substituted benzamide (3) or (8; R = primary alkyl, phenyl) by reaction with trimethylsilyl triflate, with phosgene in ether affords the benzoselenazine-2,4-dione ring system (7) or (9) in good yield.