Amino acid-derived bisphenolate palladium complexes as C-C coupling catalysts.
Amino acid-derived bisphenolate palladium complexes as C-C coupling catalysts.
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氨基酸衍生的双酚钯配合物作为 C-C 偶联催化剂。
DOI：
10.1039/d1dt03068j
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Fazekas E
中科院分区：
文献类型：
--
作者：
Fazekas E
制备了一系列具有氨基酸酯悬垂臂的胺双酚（ABP）前配体。该合成方法的优化使得天然存在的手性氨基酸能够以最小的外消旋作用轻易地结合到ABP支架中。在胺的存在下，前配体（LH2）与Pd(OAc)2发生反应，导致在PdII中心周围形成具有前所未有的钳状O，N，O配位模式的配合物。在三烷基胺（NR3）存在下的络合作用产生了LPdNR3和LPdNHR2的混合物。后者被证明是通过不稳定的Pd(OAc)2(NHR2)2中间体在室温下的C-N裂解形成的。以吡啶为碱消除了这种脱烷基反应，导致高收率的LPd（py）配合物的形成。共制备了7种新型PdII ABP配合物，它们具有扭曲的方平面几何形状，配体不对称部分朝向金属中心。空气稳定和湿稳定的LPd（py）配合物成功地用作两种类型的C-C偶联反应的催化剂。4 ' -溴苯乙酮和苯硼酸的Suzuki-Miyaura偶联获得了高收率（高达81%），同时在低催化剂负载（1 mol%）和温和温度（40°C）下也有效地转化了一系列烷基溴。此外，pd -吡啶配合物在苯乙烯和4′-溴苯乙酮的Mizoroki-Heck偶联中具有高活性。
A series of amine bisphenol (ABP) pro-ligands featuring amino acid ester pendant arms were prepared. Optimisation of the synthetic method allowed the facile incorporation of naturally occurring, chiral amino acids into the ABP scaffold with minimal racemisation. Reaction of the pro-ligands (LH2) with Pd(OAc)2, in the presence of amines, led to the formation of complexes with an unprecedented pincer-like O,N,O coordination mode around the PdII centre. The complexations in the presence of trialkylamines (NR3) afforded a mixture of LPdNR3 and LPdNHR2 species. The latter was shown to form via an ambient-temperature C–N cleavage involving unstable Pd(OAc)2(NHR2)2 intermediates. Using pyridine as base eliminated this dealkylation and resulted in the exclusive formation of LPd(py) complexes in high yields. In total, seven novel PdII ABP complexes were prepared, exhibiting distorted square-planar geometries with the asymmetric ligand moieties orientated towards the metal centre. The air- and moisture-stable LPd(py) complexes were successfully employed as catalysts in two types of C–C coupling reactions. The Suzuki–Miyaura coupling of 4′-bromoacetophenone and phenylboronic acid reached high yields (up to 81%), while a scope of further alkyl bromides was also efficiently converted using low catalyst loadings (1 mol%) and mild temperatures (40 °C). Furthermore, a Pd–pyridine complex achieved high activity in the Mizoroki–Heck coupling of styrene and 4′-bromoacetophenone.