On Homogeneous Gold/Palladium Catalytic Systems
On Homogeneous Gold/Palladium Catalytic Systems
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DOI：
10.1002/adsc.201000044
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发表时间：
2012-01-01
影响因子：
5.4
通讯作者：
Rominger, Frank
中科院分区：
文献类型：
--
作者：
Hashmi, A. Stephen K.;Lothschuetz, Christian;Rominger, Frank
制备了两种含有芳基碘和丙二烯酸酯的底物，并研究了金诱导的乙烯基金（I）物种的环化异构化和它们的原脱氧以及分子内钯催化的交叉偶联反应。转换为催化量的金和钯以及化学计量量的银确实提供了环异构化/分子内交叉偶联的产物。对照实验表明，在这些反应中，银不能代替金或钯，但不同氧化态的不同钯催化剂也以仅略微降低的产率提供环异构化/分子内交叉偶联产物。通过ICP分析，钯显示仅含有亚ppm水平的金。这表明如何仔细的结果得到这样的系统必须加以解释。然后研究了一系列烯丙基和苄基邻炔基苯甲酸酯在金和钯催化下的反应。对于苯甲醇和肉桂醇的酯，不需要钯助催化剂用于转化。通过ICP分析彻底检查所有试剂的钯痕量，以彻底排除金/钯共催化。金络合物、抗衡离子和溶剂的优化表明，金（I）异腈预催化剂和三氟甲磺酸银作为活化剂在二氧六环中适合于转化许多具有芳基、烷基和甚至环丙基取代基的底物。交叉实验证明了分子间的烯丙基转移。
Two substrates containing an aryl iodide and an allenoate ester were prepared and the gold-induced cycloisomerisation to vinylgold(I) species and their proto-deauration as well as the intramolecular palladium-catalysed cross-coupling reactions were investigated. Switching to catalytic amounts of gold and palladium and stoichiometric amounts of silver did indeed furnish the product of a cycloisomerisation/intramolecular cross-coupling. Control experiments revealed that silver cannot substitute for gold or palladium in these reactions, but a different palladium catalyst in a different oxidation state also afforded the cycloisomerisation/intramolecular cross-coupling products in only slightly reduced yields. By ICP analysis the palladium was shown to contain gold only at the sub-ppm level. This shows how carefully results obtained with such systems have to be interpreted. Then a series of allylic and benzylic o-alkynylbenzoates were investigated in gold- and palladium-catalysed reactions. For esters of benzyl alcohol and cinnamyl alcohol no palladium co-catalyst was needed for the conversion. All reagents were thoroughly checked for palladium traces by ICP analysis in order to thoroughly exclude a gold/palladium co-catalysis. Optimisation of the gold complex, counter ion and solvent showed that gold(I) isonitrile pre-catalysts and silver triflate as activator in dioxane are suitable to convert a number of substrates with aryl, alkyl and even cyclopropyl substituents. Crossover experiments proved an intermolecular allyl transfer.