Enantioselective Vanadium-Catalyzed Oxidative Coupling: Development and Mechanistic Insights
作者:Houng Kang、Madison R. Herling、Kyle A. Niederer、Young Eun Lee、Peddiahgari Vasu Govardhana Reddy、Sangeeta Dey、Scott E. Allen、Paul Sung、Kirsten Hewitt、Carilyn Torruellas、Gina J. Kim、Marisa C. Kozlowski
DOI:10.1021/acs.joc.8b02083
日期:2018.12.7
vanadium catalyst for enantioselective oxidative coupling of phenols is reported, ultimately resulting in a simple monomeric vanadium species combined with a Brønsted or Lewis acid additive. The resultant vanadium complex is found to effect the asymmetric oxidative ortho–ortho coupling of simple phenols and 2-hydroxycarbazoles with good to excellent levels of enantioselectivity. Experimental and quantum
据报道,用于苯酚的对映选择性氧化偶合反应的反应性更强的手性钒催化剂的发展,最终导致与布朗斯台德或路易斯酸添加剂结合的简单单体钒物种。发现所生成的钒配合物会影响不对称氧化邻位-邻位简单的酚和2-羟基咔唑的对映选择性良好至极好。该机理的实验和量子力学研究表明,添加剂使钒单体聚集。另外,在碳-碳键形成之前,涉及单重态到三重态的交叉。导致对映体产物的两个最低能量的非对映体过渡态在涉及较小的对映体的路径上有很大不同,所述较小的对映体在两个酚部分之间具有较大的扭转应变。