Enantioselective Photoredox Catalysis Enabled by Proton-Coupled Electron Transfer: Development of an Asymmetric Aza-Pinacol Cyclization
作者:Lydia J. Rono、Hatice G. Yayla、David Y. Wang、Michael F. Armstrong、Robert R. Knowles
DOI:10.1021/ja4100595
日期:2013.11.27
protocol for the reductive coupling of ketones and hydrazones is reported. These reactions proceed through neutral ketyl radical intermediates generated via a concerted proton-coupled electron transfer (PCET) event jointly mediated by a chiral phosphoric acid catalyst and the photoredox catalyst Ir(ppy)2(dtbpy)PF6. Remarkably, these neutral ketyl radicals appear to remain H-bonded to the chiral conjugate
报道了第一个用于酮和腙还原偶联的高度对映选择性催化方案。这些反应通过由手性磷酸催化剂和光氧化还原催化剂 Ir(ppy)2(dtbpy)PF6 共同介导的协同质子耦合电子转移 (PCET) 事件产生的中性羰基自由基中间体进行。值得注意的是,在随后的 CC 键形成步骤过程中,这些中性羰基自由基似乎保持与布朗斯台德酸的手性共轭碱 H 键合,从而提供具有优异水平的非对映选择性和对映选择性的顺式 1,2-氨基醇衍生物. 这项工作首次证明了不对称催化中协同 PCET 活化的可行性和潜在益处。
Iodomesitylene-Catalyzed Oxidative Cleavage of Carbon−Carbon Double and Triple Bonds Using <i>m</i>-Chloroperbenzoic Acid as a Terminal Oxidant
Transition metal-catalyzed oxidativecleavage of carbon-carbon multiple bonds has emerged as a powerful tool in organic synthesis. High-valent oxometals, mostly of Ru, Os, Mn, Mo, W, and Re, were used catalytically as reactive oxygen transfer agents to the multiple bonds. Reported here for the first time are the organocatalytic versions of the oxidativecleavage reactions. Our method involves use of
Nickel-catalyzed cross-couplings of cyclohexenyl phosphate and arylboronic acids
作者:Yang Nan、Zhen Yang
DOI:10.1016/s0040-4039(99)00517-1
日期:1999.4
The Nickel-catalyzedcross-coupling reaction of cyclohexenylphosphate with a variety of arylboronicacids is described here for the first time. This methodology opens the door to other palladium or nickel-catalyzed coupling reactions involving vinyl phosphates.
Enantioselective Nickel-Catalyzed Alkyne–Azide Cycloaddition by Dynamic Kinetic Resolution
作者:En-Chih Liu、Joseph J. Topczewski
DOI:10.1021/jacs.1c01354
日期:2021.4.14
α-chiral, being derived from amino acids. This makes α-N-chiral triazoles attractive building blocks. This report describes the first enantioselective triazole synthesis that proceeds via nickel-catalyzed alkyne–azide cycloaddition (NiAAC). This dynamic kineticresolution is enabled by a spontaneous [3,3]-sigmatropic rearrangement of the allylic azide. The 1,4,5-trisubstituted triazole products, derived
here for the first time are the developments of an efficient method for oxidativecleavage of carbon−carbon double bonds yielding carbonyl compounds by using aryl-λ3-iodanes, which involve a combination of iodosylbenzene and HBF4 in the presence of water. The method serves as a safety alternative to ozonolysis. The oxidativecleavage of olefins probably involves the hitherto unknown direct vicinal dihydroxylations