TY - JOUR
T1 - Quantum chemical calculations on the photochemistry of germacrene and germacrol. The exclusive role of the exocyclic double bond isomerization
AU - Peijnenburg, W.J.G.M.
AU - Dormans, G.J.M.
AU - Buck, H.M.
PY - 1988
Y1 - 1988
N2 - The different photochemistry of the title compounds (reactions of the endocyclic 1,5-dlene moiety versus a photochemical [1,3]-OH shift) can be explained assuming an initial isomerization of the exocyclic double bond. MNDO/CI calculations of the potential energy curves and nonadiabatic couplings for the rotation of this bond showed that the 90° twisted conformation can easily be reached. For germacrol the lowest excited state has a zwitterionic character which is favourable for a planar photochemical [1,3]-OH shift. For germacrene, this polarized state is strongly coupled to two diradicalar states. In these twisted diradicalar states a redistribution of the charges in the endocyclic double bonds is found which is eminently suited for intramolecular bond formation.
AB - The different photochemistry of the title compounds (reactions of the endocyclic 1,5-dlene moiety versus a photochemical [1,3]-OH shift) can be explained assuming an initial isomerization of the exocyclic double bond. MNDO/CI calculations of the potential energy curves and nonadiabatic couplings for the rotation of this bond showed that the 90° twisted conformation can easily be reached. For germacrol the lowest excited state has a zwitterionic character which is favourable for a planar photochemical [1,3]-OH shift. For germacrene, this polarized state is strongly coupled to two diradicalar states. In these twisted diradicalar states a redistribution of the charges in the endocyclic double bonds is found which is eminently suited for intramolecular bond formation.
U2 - 10.1016/S0040-4020(01)81743-9
DO - 10.1016/S0040-4020(01)81743-9
M3 - Article
VL - 44
SP - 2339
EP - 2350
JO - Tetrahedron
JF - Tetrahedron
SN - 0040-4020
IS - 8
ER -