Regioselective photocycloaddition of pyridine derivatives to electron-rich alkenes.
Irradiation of a benzene solution of 3-cyano-2,6-dimethoxypyridine in the presence of ethyl vinyl ether (EVE) gave 1:1 photoadducts, 3-cyano-5-ethoxy-2,8-dimethoxy-4,5-dihydroazocine, in good yields, whose structure was established by X-ray single-crystal analysis. The photoadduct was produced via cycloaddition between the C3-C4 position of the pyridine derivatives and an alkene chromophore. On the other hand, 3-cyano-2,6-dimethoxy-4-methylpyridine cycloadds to EVE at the C2-C3 position of the pyridine ring upon irradiation. The difference is explained on the basis of the steric effect.
Sakamoto
Masami
M
Department of Materials Technology, Faculty of Engineering, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. sakamotom@faculty.chiba-u.jp
Sano
Takeru
T
Fujita
Shohei
S
Ando
Masaru
M
Yamaguchi
Kentaro
K
Mino
Takashi
T
Fujita
Tsutomu
T