Facile Rearrangement of the 6,11-Diphenyldibenzo[b,f][1,4]diazocine Skeleton into a Substituted 2-(2-Aminophenyl)-1,3-diphenylisoindole via Anomalous Carbo­lithiation or Hydrolithiation: Corroboration of Operative SET Processes

The starting 6,11‐diphenyldibenzo[b,f][1,4]diazocine has been individually treated with R–Li reagents in THF, where R = AlH4, PhCH2, Ph2CH, Ph3C, CH3, CH3(CH2)3, C6H5 or Ph–C≡C, to learn whether an expected 1,2‐ or 1,4‐addition would cleanly occur. Contrary to such an assumption based on nucleophilic attack, this [1,4]diazocine with PhCH2Li yielded only the enantiomers of (4b,11R)‐11‐benzyl‐4b,11‐diphenyl‐4b,11‐dihydro‐5H‐benzo[4,5]imidazo[2,1‐a]isoindole; with Ph2CHLi yielded 2‐[1‐(4‐benzhydrylphenyl)‐phenyl‐2H‐isoindol‐2‐yl]analine; and with LiAlH4 2‐(2‐aminophenyl)‐1,3‐diphenylisoindole. Finally, individual reactions of the [1,4]diazocine with CH3Li, nBuLi or PhLi gave 4–5 inseparable products, instead of any simple 1,2 or 1,4 adduct. The anomalous carbolithiations and hydrolithiation observed are irreconcilable with a nucleophilic mechanism but in excellent accord with a SET radical‐anion pathway. Attempted 1,2‐carbolithiation or hydrolithiation of 6,11‐diphenyldibenzo[b,f][1,4]diazocine with benzyllithium, benzhydryllithium or lithium aluminum hydride led instead to anomalous additions involving skeletal rearrangements having SET character.