Electronically flexible PYA ligands for efficient palladium-catalyzed α-arylation of ketones
作者:Esaïe Reusser、Martin Albrecht
DOI:10.1039/d3dt03182a
日期:——
Palladium-catalyzed cross-coupling chemistry and in particular ketone α-arylation has been relying on a rather narrow range of supporting ligands with almost no alternatives to phosphines and N-heterocyclic carbenes. Here we introduce a class of well-defined palladium(II) complexes supported by N,N′-chelating and electronically flexible pyridylidene amide (PYA)-pyridyl ligands as catalysts for efficient
钯催化的交叉偶联化学,特别是酮的 α-芳基化一直依赖于相当窄范围的支持配体,几乎没有膦和 N-杂环卡宾的替代品。在这里,我们介绍了一类由N , N '-螯合和电子柔性吡啶基酰胺 (PYA)-吡啶基配体支撑的明确的钯 ( II ) 配合物,作为酮有效 α-芳基化的催化剂。N , N'-二齿配体的空间和电子变化表明,在PYA配体的吡啶杂环上引入邻甲基基团可提高芳基化速率并防止催化剂失活,周转数高达7300,周转频率为几乎10 000 h -1,这与迄今为止已知的最好的膦配合物相似。引入屏蔽二甲苯基取代基进一步加速催化,但代价是对芳基化酮的选择性较低。底物范围研究表明,富电子和贫电子芳基溴以及各种电子和空间修饰的酮都可以有效转化,包括脂肪族酮。使用 Hammett 和 Eyring 分析进行的机理研究表明,氧化加成和还原消除都相对较快,这可能是 PYA 配体的电子灵活性的结果,而烯醇配位被确定为转换限制步骤。
Modulation of N^N′-bidentate chelating pyridyl–pyridylidene amide ligands offers mechanistic insights into Pd-catalysed ethylene/methyl acrylate copolymerisation
作者:Gearóid M. Ó Máille、Anna Dall'Anese、Philipp Grossenbacher、Tiziano Montini、Barbara Milani、Martin Albrecht
DOI:10.1039/d1dt00389e
日期:——
Careful ligand design led to the detection of either an unprecedented, stable, 4-membered palladacycle or an off-cycle catalyst degradation product.