1,3-Dipolar cycloaddition of α-alkoxycarbonylnitrones with vinyl ethers and allyl alcohols in the presence of Eu(fod)3: selective activation of (Z)-isomers of the nitrones
作者:Osamu Tamura、Naka Mita、Yasuharu Imai、Takuya Nishimura、Tamiko Kiyotani、Mikio Yamasaki、Motoo Shiro、Nobuyoshi Morita、Iwao Okamoto、Tetsuya Takeya、Hiroyuki Ishibashi、Masanori Sakamoto
DOI:10.1016/j.tet.2006.10.014
日期:2006.12
Uncatalyzed cycloaddition of α-alkoxycarbonylnitrones 1 with vinyl ethers 7 gave mixtures of cis- and trans-cycloadducts 8, whereas Eu(fod)3-catalyzed cycloaddition of 1 with 7 gave the trans-cycloadducts trans-8 in a highly stereoselective manner. NMR studies indicated that Eu(fod)3 selectively activated (Z)-nitrones (Z)-1 in E,Z-equilibrium mixtures of nitrones 1. In contrast, the reaction of 1 with
α-alkoxycarbonylnitrones的非催化环加成1与乙烯基醚7,得到的混合物的顺式-和反式-cycloadducts 8,而铕(FOD)3的催化的环加成1与7,得到反式-cycloadducts反式- 8在高度立体选择性的方式。NMR研究表明,铕(FOD)3选择性地激活(ż)-nitrones(Ž) - 1中ë,ž -equilibrium硝酮的混合物1。相反,在Eu(fod)3存在下1与烯丙醇12的反应导致顺序酯基转移和分子内环加成反应产生分子内环加合物13。