A Proton-Responsive Annulated Mesoionic Carbene (MIC) Scaffold on Ir Complex for Proton/Hydride Shuttle: An Experimental and Computational Investigation on Reductive Amination of Aldehyde
作者:Pragati Pandey、Prosenjit Daw、Noor U Din Reshi、Kira R. Ehmann、Markus Hölscher、Walter Leitner、Jitendra K. Bera
DOI:10.1021/acs.organomet.0c00568
日期:2020.11.9
A Cp*Ir(III) complex (1) bearing a proton-responsive hydroxy unit on an annulated imidazo[1,2-a][1,8]naphthyridine based mesoionic carbene scaffold was synthesized by two different synthetic routes. The molecular structure of 1 revealed an anionic lactam form of the ligand. The acid–base equilibrium between the lactam-lactim tautomers on the ligand scaffold was examined by 1H NMR and UV–vis spectra
通过两种不同的合成途径合成了在环状咪唑并[1,2- a ] [1,8]萘吡啶基介电卡宾骨架上带有质子响应性羟基单元的Cp * Ir(III)配合物(1)。的分子结构1揭示了配体的阴离子内酰胺形式。通过1 H NMR和UV-vis光谱检查了配体支架上内酰胺-内酯互变异构体之间的酸碱平衡。估算内酰胺形式为1的附件-OH基团的p K a,以评估催化剂的质子转移性能。1的催化功效通过使用三种不同的氢源(分子H 2,i PrOH / KO t Bu组合和HCOOH / Et 3 N(5:2)共沸混合物)评估醛的还原胺化反应。发现在三种不同的氢化方法中,HCOOH / Et 3 N(5:2)共沸混合物是最好的。在反应条件下,催化剂1在羰基上化学选择性地氢化亚胺。使用HCOOH / Et 3 N(5:2)共沸混合物将一系列醛还原为相应的仲胺。此外,催化剂1在还原多种N-杂环亚胺衍生物方面显示出高效率。提