Mechanism of Cyclization of Divinyl-N-phenylboranamines

Article abstract of DOI:10.1021/ja00390a025

High-resolution NMR and mass spectral data were used to deduce the mechanism of nonoxidative photocyclization of divinyl-N-phenylboranamines.Cyclization was found to proceed through an excited singlet state conrotatory electrocyclic ring closure between phenyl and ajacent vinyl groups, followed by an intramolecular suprafacial 1,5-hydrogen shift.Such a mechanism was found to be operating in both the divinylboranamines and the dicycloalkenylboranamines.Irradiation in acetonitrile inhibited vinylic photochemical trans-cis isomerization, yielding predominantly the cycloadduct fron starting material vinyl stereochemistry.