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首页> 外文期刊>Chemistry: A European journal >Mild, single-pot hydrocarboxylation of gaseous alkanes to carboxylic acids in metal-free and copper-promoted aqueous systems
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Mild, single-pot hydrocarboxylation of gaseous alkanes to carboxylic acids in metal-free and copper-promoted aqueous systems

机译：在无金属和铜促进的水性体系中，气态烷烃温和的单锅加氢羧化为羧酸

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摘要

A direct, selective and highly efficient method has been developed for the hydrocarboxylation of C_n gaseous alkanes into C_(n+1) carboxylic acids, in aqueous acid-solvent-free medium at low temperatures. The approach is based on a metal-free or copper-promoted reaction of ethane, propane or n-butane with carbon monoxide and water, in a H_2O/MeCN medium at 50-60 °C, in the presence of potassium peroxodisulfate. The effects of various reaction parameters, such as the absence or presence of a copper promoter, solvent composition, temperature, time, CO and alkane pressure, were studied. A free radical mechanism was confirmed by radical trap experiments involving acyl radical formation, oxidation and subsequent hydroxylation by water. Remarkable yields (based on alkane) of carboxylic acids in the 34- 41% range were achieved even in the metal-free systems, although in the presence of a tetracopper(II) triethanolaminate derived promoter they reach superior values of 58 and 87% for the hydrocarboxylations of propane and nbutane, respectively; in these cases, branched isobutyric and 2-methylbutyric acids were the predominant products. From a green perspective, important features of the present alkane hydrocarboxylations include the exceptional metal-free, mild and acid-solvent- free reaction conditions, the operation in aqueous medium with a rare hydroxylating role of water, with high selectivities, and yields of carboxylic acids. Taken together, these conditions correspond to the mildest and the most efficient method so far reported for the oxidative functionalisation of gaseous alkanes.
机译：已经开发了一种直接，选择性和高效的方法，用于在低温无酸溶剂介质中将C_n气态烷烃加氢羧化为C_（n + 1）羧酸。该方法基于在过氧二硫酸钾存在下，在H_2O / MeCN介质中，50-60°C的条件下，乙烷，丙烷或正丁烷与一氧化碳和水的无金属或铜促进反应。研究了各种反应参数的影响，例如是否存在铜助催化剂，溶剂组成，温度，时间，CO和烷烃压力。自由基捕获实验证实了自由基的机理，该实验涉及酰基自由基的形成，氧化和随后的水羟基化。即使在无金属的体系中，羧酸的收率（基于烷烃）也达到了34-41％的显着水平，尽管在四铜（II）三乙醇胺衍生的促进剂存在下，它们的优异收率分别为58和87％丙烷和正丁烷的加氢羧化反应在这些情况下，支链异丁酸和2-甲基丁酸是主要产物。从绿色的角度来看，本烷烃加氢羧化反应的重要特征包括：优异的无金属，温和和无酸溶剂的反应条件，在水介质中的操作具有罕见的水羟基化作用，高选择性以及羧酸的收率酸。总而言之，这些条件对应于迄今为止报道的用于气态烷烃氧化官能化的最温和，最有效的方法。

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