Copper-Catalyzed Silacarboxylation of Internal Alkynes by Employing Carbon Dioxide and Silylboranes
Copper-Catalyzed Silacarboxylation of Internal Alkynes by Employing Carbon Dioxide and Silylboranes
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DOI：
10.1002/anie.201207148
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Tsuji, Yasushi
中科院分区：
文献类型：
--
作者：
Fujihara, Tetsuaki;Tani, Yosuke;Tsuji, Yasushi
二氧化碳(CO2)是一种无毒、丰富和可再生的碳源。[1]这种环境友好的原料在碳-碳键形成反应中的利用是均相过渡金属催化中最重要的挑战之一。[2]到目前为止，人们已经深入研究了两种类型的二氧化碳催化转化：a)用CO2取代Ar-Y(方案1a)和b)C-C不饱和物的羟基化(方案1b)。前者包括有机锌[3a，b]和有机硼烷[3c-f]的羧化反应，C±H键，[3g-j]和溴代芳烃[3k](方案1a)。最近，我们报道了在常温下，在锰粉存在下，镍催化的氯芳烃与二氧化碳的羧化反应。[4a]至于氢羧化反应(方案1b)，已经报道了二烯、[5a，b]烯、[5c]和[5d]的反应。然而，在所有这些情况下，必须使用高活性和易燃的Et3Al[5a，b]或Et2Zn[5a，c，d]作为氢化物来源。我们最近报道了使用稳定和易于操作的氢硅烷作为氢化物来源的炔烃的氢羧化反应。[4B]除了这些反应外，催化杂羧化反应非常有用，在该反应中，杂原子官能团和二氧化碳同时催化结合到不饱和底物中，因为该反应将提供一条利用二氧化碳合成高度官能化的羧酸衍生物的有价值的合成路线。对于炔烃的硅羧化，唯一的先例是Fleming等人报道的1-己炔的化学计量反应(一个例子)，他们进行了1-己炔与化学计量比的(Me2PhSi)2CuLi·LiCN的反应，然后用二氧化碳捕获生成的铜物种(方案2a)。[6]在这里，我们报道了第一次在铜催化剂的存在下，以二氧化碳和硅基硼烷催化的内部炔烃的硅羧化反应(方案2b)。[7]该反应提供了区域选择性的硅丙内酯产物。
Carbon dioxide (CO2) is a nontoxic, abundant, and renewable carbon source.[1] The utilization of this environmentally friendly raw material in carbon–carbon bond-forming reactions is one of the most important challenges in homogeneous transition metal catalysis.[2] To date, two types of catalytic transformations using CO2 with CÀC bond formation have been investigated intensively: a) the substitution of Ar–Y with CO2 (Scheme 1 a) and b) the hydrocarboxylation of C–C unsaturates (Scheme 1b). The former reactions involve the carboxylations of organozinc [3a, b] and organoborane [3c–f] compounds, CÀH bonds,[3g-j] and bromoarenes [3k](Scheme 1 a). Recently, we reported the Ni-catalyzed carboxylation of chloroarenes with CO2 in the presence of Mn powder under ambient conditions.[4a] As for the hydrocarboxylation (Scheme1b), the reactions of dienes,[5a, b] alkenes,[5c] and alkynes [5d] have been reported. However, in all these cases, highly reactive and pyrophoric Et3Al [5a, b] or Et2Zn [5a, c, d] must be used as a hydride source. We recently reported the hydrocarboxylation of alkynes, by employing stable and easyto-handle hydrosilanes as the hydride source.[4b]Besides these reactions, catalytic heterocarboxylation, in which the heteroatom functionality and CO2 are simultaneously and catalytically incorporated into unsaturated substrates, is extremely useful, since the reaction will provide a valuable synthetic route employing CO2 for the formation of highly functionalized carboxylic acid derivatives. For the silacarboxylation of alkynes, the only precedent is the stoichiometric reaction of 1-hexyne (one example) reported by Fleming et al., who carried out the reaction of 1-hexyne with a stoichiometric amount of (Me2PhSi) 2CuLi· LiCN followed by trapping of the resulting Cu species with CO2 (Scheme 2 a).[6] Herein, we report the first catalytic silacarboxylation of internal alkynes employing CO2 and silylborane in the presence of a copper catalyst (Scheme2b).[7] The reaction afforded silalactone products regioselectively in good to high yields.