Copper-catalyzed tandem [2,3]-rearrangement and 6pi-3-azatriene electrocyclization in (E)-O-propargylic alpha,beta-unsaturated oximes.
Cu-catalyzed cyclizations of (E)-O-propargylic oximes of alpha,beta-unsaturated aldehydes were successfully carried out to afford the corresponding pyridine oxides in good to high yields. As an example, (E)-acrylaldehyde O-1,3-diphenylprop-2-ynyl oxime (1b) was reacted for 5 h in the presence of CuBr(PPh(3))(3) (10 mol %) and PPh(3) (10 mol %) in DMSO at 120 degrees C to afford 3-benzyl-2-phenylpyridine-N-oxide (2b) in 84% yield. In this case, the reaction proceeded via Cu-catalyzed propargyl oxime-allenyl nitrone rearrangement followed by 6pi-3-azatriene electrocyclization.
Nakamura
Itaru
I
Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. itaru-n@m.tains.tohoku.ac.jp
Zhang
Dong
D
Terada
Masahiro
M