TY - JOUR
T1 - Novel, intramolecular hydrogen-transfer and cyclo-addition photochemistry of cyclic 1,3-dienes
AU - Miesen, F.W.A.M.
AU - Baeten, H.C.M.
AU - Langermans, H.A.
AU - Koole, L.H.
AU - Claessens, H.A.
PY - 1991
Y1 - 1991
N2 - With use of one- and two-dimensional NMR spectroscopy and deuterium labelling, the photochemistry of 9-endo-hydroxy-9-exo-vinyl-bicyclo[4.2.1]nonadiene (1) and the 9-exo-(11-dimethylvinyl)- (2) and 9-exo-ethyl- (3) analogues has been studied. Irradiation of 1–3 gave novel 8-membered ring systems 4–6 by a light-induced rearrangement process, in which the hydroxyl proton is transferred on one side of the molecule toward one of the termini of the endocyclic diene. This rearrangement process thus involves a formal hydrogen transfer, during which either H+ or H• may be transferred to a reactive diene intermediate. Replacement of the hydroxyl proton by deuterium in 1–3, and 2H NMR of the corresponding photoproducts, confirmed that the hydrogen translocation occurs intramolecularly. Prolonged irradiation of 4 and 5 results in the formation of pyran products 10 and 11 by an intramolecular photocycloaddition of the triplet excited state of the a,ß-unsaturated ketone to 1,3-cis,cis-cyclooctadiene, via a stabilized bisallylic biradical intermediate. Conformational studies of the structurally more rigid system 10, which is derived from 4, revealed that the hydroxyl proton was transferred on the endo side of the molecule
AB - With use of one- and two-dimensional NMR spectroscopy and deuterium labelling, the photochemistry of 9-endo-hydroxy-9-exo-vinyl-bicyclo[4.2.1]nonadiene (1) and the 9-exo-(11-dimethylvinyl)- (2) and 9-exo-ethyl- (3) analogues has been studied. Irradiation of 1–3 gave novel 8-membered ring systems 4–6 by a light-induced rearrangement process, in which the hydroxyl proton is transferred on one side of the molecule toward one of the termini of the endocyclic diene. This rearrangement process thus involves a formal hydrogen transfer, during which either H+ or H• may be transferred to a reactive diene intermediate. Replacement of the hydroxyl proton by deuterium in 1–3, and 2H NMR of the corresponding photoproducts, confirmed that the hydrogen translocation occurs intramolecularly. Prolonged irradiation of 4 and 5 results in the formation of pyran products 10 and 11 by an intramolecular photocycloaddition of the triplet excited state of the a,ß-unsaturated ketone to 1,3-cis,cis-cyclooctadiene, via a stabilized bisallylic biradical intermediate. Conformational studies of the structurally more rigid system 10, which is derived from 4, revealed that the hydroxyl proton was transferred on the endo side of the molecule
U2 - 10.1139/v91-230
DO - 10.1139/v91-230
M3 - Article
SN - 0008-4042
VL - 69
SP - 1554
EP - 1562
JO - Canadian Journal of Chemistry
JF - Canadian Journal of Chemistry
IS - 10
ER -