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

N -(4-Biphenylyl)- N -cyclopropyl nitrenium ion 5 and N -benzyl- N -cyclopropyl nitrenium ion ( 6 ) were generated through photolysis of their corresponding N -aminopyridinium ion photoprecursors. In the case of 5 , stable products result from a combination of cyclopropyl ring expansion ( N -biphenylazetium ion) and ethylene elimination (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 the N -benzyl- N -cyclopropyl nitrenium ion ( 6 ) is benzylisonitrile, resulting from the elimination of ethylene. Density functional theory (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.