Addition, Elimination, and Rearrangement Reactions of Cyclopropyl-Substituted Nitrenium Ions: A Computational and Experimental Investigation

Two cyclopropyl substituted nitrenium ions were generated through photolysis of their corresponding N-aminopyridinium ion photoprecursors. In the case of N-biphenyl-N-cyclopropyl nitrenium ion (5). Stable products are derived from a combination of cyclopropyl ring expansion, forming N-biphenylazetium ion, and ethylene elimination, forming biphenylisonitrilium ion. When present in high concentrations, methanol can add to the cyclopropyl ring forming N-3-methoxypropyl-N-biphenyl iminium ion. In contrast, the only detectable product from N-benzyl-N-cyclopropyl nitrenium ion (6) is benzylisonitrile, resulting from elimination of ethylene. DFT calculations predict the product distributions from the more stable biphenyl system 5 with reasonable accuracy. However product distributions from the less stable benzyl system 6 are forecast with less accuracy.