Photorearrangement of vinylidenecyclopropanes to 1,2,3-butatriene derivatives.
[reaction: see text] Photoirradiation of benzene solutions containing 1-diarylvinylidene-2,2,3,3-tetramethylcyclopropanes (2a--d) afforded rearranged products 1,2,3-butatrienes (3a-d) in good to high yields. Photorearrangement from 2,2,3-trimethyl and 2,2- and 2,3-dimethyl derivatives 2e--g also proceeded, but the rates of the rearrangement were lower than those of 2a--d. A singlet mechanism is proposed for this photorearrangement, where alkyl migration occurs from 1,3-biradical intermediates generated via the homolysis of the C1-C2 bond. Generation of diarylvinylidene carbenes from 1,3-biradicals might be competitive with the formation of 3.
Mizuno
K
K
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Japan. mizuno@chem.osakafu-u.ac.jp
Maeda
H
H
Sugita
H
H
Nishioka
S
S
Hirai
T
T
Sugimoto
A
A