Applications of MCD Spectroscopy: MO Ordering and Transannular Interaction in 1,6-Methanoannulenes from Analysis of Substituent Effects

Article abstract of DOI:10.1021/ja00349a001

Eight 2-substituted and nine 3-substituted 1,6-methano<10>annulenes have been synthesized, and their magnetic circular dichroism has been measured.The B terms of the L_b transition depend on the ?-electron effect of the substituent in a way which reveals the ordering of the four frontier molecular orbitals: a₁, a₂, b₁, and b₂ in the order of increasing energy.This result implies the presence of a strong transannular interaction between the bridgehead positions 1 and 6 on the bridged <10>annulene ring.