Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
J Am Chem Soc. 2010 Jun 16;132(23):7884-6. doi: 10.1021/ja102436z.
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.
(E)-O-炔丙基肟-α,β-不饱和醛在铜催化下发生环化反应，以良好到较高的收率得到相应的吡啶氧化物。例如，（E）-丙烯醛 O-1,3-二苯基丙-2-炔基肟（1b）在 120°C 下，在 DMSO 中，CuBr(PPh(3))(3)（10mol%）和 PPh(3)（10mol%）的存在下反应 5 小时，以 84%的收率得到 3-苄基-2-苯基吡啶-N-氧化物（2b）。在这种情况下，反应通过铜催化的炔丙基肟-烯丙基硝酮重排，接着是 6pi-3-氮杂环丙烯电环化进行。
