A general and efficient method for the formylation of aryl and heteroaryl bromides
A general and efficient method for the formylation of aryl and heteroaryl bromides
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DOI：
10.1002/anie.200502697
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Beller, M
中科院分区：
文献类型：
--
作者：
Klaus, S;Neumann, H;Beller, M
基于我们在羰基化反应中的经验，[17]我们开始探索我们的配体在芳基卤化物的还原羰基化反应中的潜力。在这里，我们描述了我们的调查，这导致了最普遍的，活性和生产钯催化剂迄今已知的芳基和杂芳基溴的还原羰基化的第一个结果。最初在模型系统中研究了4-溴苯甲醚（失活的芳基溴）的分解（表1）。通常，所有实验都在改进的六重并联高压釜中进行，这允许快速测试催化剂和条件。关于适合于实际应用的条件，应用低催化剂负载（<0.5mol%）和存在最经济的甲酰基源（其为合成气）。使用三倍过量的配体（P/Pd= 3：1）来稳定钯催化剂并防止钯羰基簇的形成。在我们的研究中，在100 ℃和低压（5巴CO/H2= 1：1）下测试了超过20种膦和卡宾配体（方案2）。令人满意的是，在这些条件下，不需要使用昂贵的高压钢高压釜设备，因为也可以在更简单的玻璃高压釜中进行反应。表1显示了所得结果的总结。标准的二齿配体如1，3-双（二苯基膦基）丙烷（dppp，1a）、1，4-双（二苯基膦基）丁基（dppp，1a）、1，
Based on our experience of carbonylation reactions,[17] we started to explore the potential of our ligands in reductive carbonylations of aryl halides. Here, we describe the first results of our investigations, which led to the most general, active and productive palladium catalyst known to date for reductive carbonylations of aryl and heteroaryl bromides. The formylation of 4-bromoanisole (deactivated aryl bromide) was initially investigated in a model system (Table 1). Typically, all experiments were carried out in a modified sixfold-parallel autoclave, which allows a rapid testing of catalysts and conditions. With regard to conditions suitable for practical applications, low catalyst loadings (< 0.5 mol%) and the presence of the most economical formyl source, which is synthesis gas, were applied. A threefold excess of the ligand (P/Pd= 3: 1) was used to stabilize the palladium catalyst and to prevent the formation of palladium carbonyl clusters. More than 20 phosphine and carbene ligands (Scheme 2) were tested at 1008C and low pressure (5 bar CO/H2= 1: 1) in our study. Gratifyingly, under these conditions it is not necessary to use expensive highpressure steel autoclave equipment, as it is also possible to perform the reactions in simpler glass autoclaves. Table 1 shows a summary of the results obtained. Standard bidentate ligands such as 1, 3-bis (diphenylphosphanyl) propane (dppp, 1a), 1, 4-bis (diphenylphosphanyl) bu-