Site-selective and stereoselective intramolecular (2pi + 2pi) photocycloaddition of arylalkenes to pyrene and its photocycloreversion
Irradiation of a benzene solution containing methyl p-(1-pyrenylmethoxymethyl)cinnamate (1a) with a high-pressure Hg lamp through Pyrex filter stereoselectively gave an intramolecular (2pi + 2pi) photocycloadduct (2a) in an 83% yield in a site-selective manner at the 4,5-position of the pyrene ring. Similar irradiation of an ortho-substituted derivative (3) afforded the corresponding (2pi + 2pi) cycloadduct (4) as a sole product at the 9,10-position of pyrene. The site-selective photocycloaddition can be reasonably explained by the intramolecular sandwich-type singlet exciplexes between the pyrene and phenyl rings.
Maeda
H
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
Sugimoto
A
Mizuno
K