Proximity effect in bergman cyclization: a semiempirical AM1 investigation

摘要

Semiempirical quantum chemical methodology (AM1) with limited configurtion interactions has been employed to explore the proximity effect on Bergman cyclization process. The energy profiles of the acyclic enediyne (Z)-hexa-1,5-diyne-3-ene 1 and a series of monocyclic enediynes have been determined considering the newly formed C-C bond distance as the reaction coordinate. The theory adequately reproduces the experimentally observed pi-bond proximity effect on activation barrier in Bergman cyclization reaction.