Loss of hydroxyl radical from cis‐ and trans‐1‐cyclohexyl 2‐phenyl‐3‐benzoylaziridines: A unique eight‐centered rearrangement elimination

Following electron impact ionization of the title compounds, a rapid electrocyclic ring opening of the [M]⁺˙ of both isomers occurs. A subsequent fragmentation of each is loss of hydroxyl which occurs by rearrangement to the carbonyl function. Properties of [MOH]⁺ are in accord with a stable structure for this ion and therefore it is assigned as the 4‐phenylisoquinium ion. The proposed mechanism and ion structures are supported by deuterium labeling and defocused metastable ion studies.