The reactions of nitrosobenzenes have been the subject of much study and many publications. However, not unlike other projects, at least as many questions have been raised as have been answered. There are several nitrosobenzene reactions which are of particular interest to us and we would like to raise a few more questions concerning their mechanisms. Nitrosoarenes are reported to undergo cycloaddition reactions with diphenylketene to yield 3 or 4-oxazetidinones depending upon ring substituents in the nitrosoarene.1More recently nitrosoarenes have been shown to undergo a similar cycloaddition reaction with ketenimines (nitrogen analogs of ketenes), but only the 3-iminosubstituted oxazetidine (the isomer unexpected from polar theory) is obtained regardless of ring substituents in the nitrosoarene.2A related problem is the 1,4-cycloaddition of nitrosobenzene and cycloheptadiene and the 1,6-cycloaddition of nitrosobenzene and cycloheptatriene.3,4The observed differences in products have been attributed to a variation in the mode of reaction.4Concerted processes were postulated to give 1,4-addition while stepwise processes lead to 1,6-addition.