Symmetry-enforced conformational control of photochemical reactivity in 2-vinyl-1,3-terphenyl.
The photocyclization of o-vinylbiphenyl to 9,10-dihydrophenanthrene occurs with very low quantum yield because of the low ground-state population of the reactive syn rotamer. 2-Vinyl-1,3-terphenyl exists as a single rotamer which undergoes highly efficient photocyclization. Irradiation at 77 K in a rigid glass permits observation of the 8a,9-dihydrophenanthrene which rearranges to the 9,10-dihydrophenanthrene upon warming of the glass. The barriers for photocyclization and the thermal sigmatropic hydrogen shift are both remarkably small.
Lewis
Frederick D
FD
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA. lewis@chem.nwu.edu
Zuo
Xiaobing
X
Gevorgyan
Vladimir
V
Rubin
Michael
M