Migratory decarboxylative coupling of coumarins: synthetic and mechanistic aspects.
Migratory decarboxylative coupling of coumarins: synthetic and mechanistic aspects.
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DOI：
10.1002/anie.201100765
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发表时间：
2011-05-23
影响因子：
16.6
通讯作者：
Tunge, Jon A.
中科院分区：
文献类型：
--
作者：
Jana, Ranjan;Partridge, James J.;Tunge, Jon A.
通过脱羧偶联来构建新的C2 H2 C键是一种强大的合成方法，因为它避免了产生化学计量金属废物的高度碱性反应条件和预先形成的有机金属试剂。[1]此外，副产物（CO2）无毒，不需要特殊的分离程序。因此，几个研究小组已经证明，脱羧偶联是标准交叉偶联反应的实际替代方案。[1-6]例如，Gooßen和同事已经报道了苯甲酸与卤代芳族化合物的Pd II催化偶联以产生联芳基产物。[3]此外，Myers等人已经展示了Heck反应的Pd II催化的脱羧变体。[4]我们的研究主要集中在脱羧烯丙基化和苄基化反应的发展。[5]在这个竞技场中，我们已经报道了在温和条件下杂芳族香豆素底物的脱羧烯丙基化（DcA）[Eq.（1）]。[6]香豆素不仅是具有生物学和药学意义的“特权”支架，[7，8]而且由于其生物物理性质，它们也被广泛用于染料中。[9]在我们对香豆素的DcA的持续研究中，我们将注意力转向了对4-取代香豆素的脱羧偶联的研究。因此，合成了4-甲基-3-烯丙基香豆酸酯1a，并在508 ℃下进行我们先前的Pd 0催化的脱羧偶联条件。[6]令人惊讶的是，即使在长时间加热后，起始材料仍保持完整。然而，在1108 ° C下在甲苯中加热底物6小时后，我们观察到脱羧和C2 H2 C键形成（2a）以及质子脱羧[Eq.（2）]。通过1H NMR光谱对产物进行更仔细的分析显示，烯丙基化发生在甲基末端，提供4-高烯丙基香豆素代替
Construction of new CÀC bonds by decarboxylative coupling is a powerful synthetic method since it avoids highly basic reaction conditions and preformed organometallic reagents that produce stoichiometric metal waste.[1] In addition, the byproduct (CO2) is nontoxic and requires no special separation procedures. Thus several research groups have demonstrated that decarboxylative couplings are practical alternatives to standard cross-coupling reactions.[1–6] For example, Gooßen and co-workers have reported a PdII-catalyzed coupling of benzoic acids with haloaromatics to generate biaryl products.[3] Furthermore, Myers et al. have shown a PdII-catalyzed decarboxylative variant of the Heck reaction.[4] Our research has focused on the development of decarboxylative allylation and benzylation reactions.[5] In this arena we have reported the decarboxylative allylation (DcA) of heteroaromatic coumarin substrates under mild conditions [Eq.(1)].[6]Coumarins are not only “privileged” scaffolds of biological and pharmaceutical interest,[7, 8] but they are also widely used in dyes because of their photophysical properties.[9] In our continuing investigations of the DcA of coumarins, we turned our attention to the investigation of decarboxylative couplings of 4-substituted coumarins. Thus, 4-methyl-3-allylcoumarate 1a was synthesized and subjected to our previous conditions for Pd0-catalyzed decarboxylative coupling at 508C.[6] Disappointingly, the starting material remained intact even after prolonged heating. However, upon heating the substrate at 1108C in toluene for 6h, we observed decarboxylation and CÀC bond formation (2a) as well as protiodecarboxylation [Eq.(2)]. Closer analysis of the products by 1H NMR spectroscopy revealed that allylation occurs at the methyl terminus providing 4-homoallylcoumarin in lieu
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影响因子：
5.2
作者：
Jana R;Trivedi R;Tunge JA
通讯作者：
Tunge JA
影响因子：
15
作者：
Goossen, Lukas J.;Rodriguez, Nuria;Levy, Laura M.
通讯作者：
Levy, Laura M.
影响因子：
5.1
作者：
Ito, C;Itoigawa, M;Furukawa, H
通讯作者：
Furukawa, H
影响因子：
5.2
作者：
Grenning AJ;Tunge JA
通讯作者：
Tunge JA
影响因子：
5.2
作者：
Burger, EC;Tunge, JA
通讯作者：
Tunge, JA