Synthesis of optically active bicyclo[2.2.2]octanes. Substitution effect of the cyclohexenone ring on the sequential Michael reaction
作者:Hiroto Nagaoka、Kimiyuki Shibuya、Kaoru Kobayashi、Isao Miura、Michitaka Muramatsu、Yasuji Yamada
DOI:10.1016/s0040-4039(00)60610-x
日期:1993.6
Reactions of the cross-conjugated dienolate of 3-substituted 2-cyclohexenone 1b and 1c, 2-cyclohexenone (1d), and 2,3-disubstituted 2-cyclohexenone 1e with methyl (S)-3-(2,2-dimethyl-1,3-dioxolan-4-yl)-2-propenate (Z)-2 gave highly diastereoselectively 3b, 3c, 3d and 3e, respectively. The presence of a methyl group at C-6 on cyclohexenone ring caused the stereoselectivity to change completely, so that
3-取代的2-环己烯酮1b和1c,2-环己烯酮(1d)和2,3-二取代的2-环己烯酮1e的交叉共轭二烯酸酯与甲基(S)-3-(2,2-二甲基- 1,3-二氧杂戊环-4-基)-2-丙酸酯(Z)-2分别具有高度非对映选择性3b,3c,3d和3e。环己烯酮环上C-6处甲基的存在导致立体选择性完全改变,因此9的烯醇锂与(Z)-2和与(E)-2的反应主要产生11和分别为12。