Development and applications of remote stereocontrol using allylic organobismuth reagents
Development and applications of remote stereocontrol using allylic organobismuth reagents
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DOI：
10.1039/c3ob41931b
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发表时间：
2013-12-28
影响因子：
3.2
通讯作者：
Thomas, Eric J.
中科院分区：
文献类型：
--
作者：
Basar, Norazah;Donnelly, Sam;Thomas, Eric J.
5-苄基氧基-4-甲基戊基-2-烯基（三丁基）锡烷与碘化铋促进的醛的反应具有立体选择性，有利于(E)-1,5-抗-6-苄基氧基-5-甲基烷烃-3-烯-1-醇。类似的5-苯氧基-4-甲基戊-2-烯基溴与醛的反应也观察到类似的立体选择性，当由三碘化铋（III）与粉状锌还原制备的低价铋促进时，从而提供了“无锡”程序。4-苄基氧氧苯-2-烯基（三丁基）锡烷与碘化铋促进的醛的类似反应也具有立体选择性，但产率较低。试图用这些反应控制1,6-立体反应，结果只有适度的立体选择性。研究了产物的化学方面，特别是它们的立体选择性转化为脂肪族化合物，在脂肪链上的1,5,9,13-和1,3,5-位置上有甲基立体中心。从机理上讲，烯丙基有机铋可能参与了这两组反应，但这还没有得到证实，尽管在碘化铋介导的2-戊基锡烷反应和低价铋促进的2-戊基溴的反应中观察到相似的立体选择性，这与类似中间体的参与一致。
Reactions of 5-benzyloxy-4-methylpent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were usefully stereoselective in favour of the (E)-1,5-anti-6-benzyloxy-5-methylalk-3-en-1-ols. Similar stereoselectivity was observed for reactions of analogous 5-benzyloxy-4-methylpent-2-enyl bromides with aldehydes when promoted by a low valency bismuth species prepared by reduction of bismuth(III) triiodide with powdered zinc so providing a "tin-free" procedure. The analogous reactions of 4-benzyloxypent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were also stereoselective but gave lower yields. Attempted 1,6-stereocontrol using these reactions resulted in only modest stereoselectivities. Aspects of the chemistry of the products were studied in particular their stereoselective conversion into aliphatic compounds with methyl bearing stereogenic centres at 1,5,9,13- and 1,3,5-positions along the aliphatic chain. Mechanistically, allylic organobismuth species may be involved in both sets of reactions but this was not confirmed although the similar stereoselectivities observed for both the bismuth(III) iodide mediated reactions of the pent-2-enylstannanes and the low valency bismuth promoted reactions of the pent-2-enyl bromides are consistent with participation of similar intermediates.