Efficient Formation of Ring Structures Utilizing Multisite Activation by Indium Catalysis
Efficient Formation of Ring Structures Utilizing Multisite Activation by Indium Catalysis
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DOI：
10.1021/ja805657h
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发表时间：
2008-12-17
影响因子：
15
通讯作者：
Nakamura, Eiichi
中科院分区：
文献类型：
--
作者：
Itoh, Yoshimitsu;Tsuji, Hayato;Nakamura, Eiichi
Lewis酸性铟(III)盐，特别是在(NTF2)(3)中，以被称为锥烯反应的方式影响α-(欧米伽‘-炔基)-β-酮酯和欧米伽-炔基-β-酮酯转化为相应的环状产物。该反应可产生五至十五元环碳环和杂环，产率良好至极佳。该反应的合成特点是催化剂负载量相对较低，最佳情况下最低可达0.01mol%，五元环的形成不需要溶剂，中等环的形成只需要适度稀释的反应条件。铟盐的高活性是由于含有乙炔功能的β-酮酸酯底物的双重活化。金属铟通过形成烯醇化铟来激活β-酮酯部分，而这种金属铟通过亲电作用激活炔部分。这种由单一金属对衬底的强烈推拉激活绕过了通常与形成中大型环相关的熵和热焓因素的不利因素。该反应允许容易地形成十五元环碳环，从该碳环合成二麝香酮。
Lewis acidic indium(III) salts, in particular In(NTf2)(3), effect the conversion of alpha-(omega'-alkynyl)-beta-ketoesters; and omega-alkynyl-beta-ketoesters to the corresponding cyclic products in a manner known as the Coniaene reaction. This reaction can lead to the creation of five- to fifteen-membered-ring carbocycles and heterocycles in good to excellent yields. The synthetic features of the reaction are a relatively low catalyst loading, as low as 0.01 mol % in the best case, as well as no requirement of solvent for five-membered-ring formation and the requirement of only moderately dilute reaction conditions for medium-sized-ring formation. The high reactivity of indium salts is due to the double activation of the beta-ketoester substrate containing an acetylene function. The indium metal activates the beta-ketoester moiety by the formation of an indium enolate, and this indium metal electrophilically activates the alkyne moiety. Such a strong push-pull activation of the substrate by a single metal circumvents the disadvantage of entropic and enthalpic factors generally associated with the formation of medium- and large-sized rings. The reaction allows the ready formation of a fifteen-membered-ring carbocycle, from which di-muscone has been synthesized.