Novel ruthenium(II) complexes were obtained as a result of a stoichiometric reaction of Grubbs’ benzylidene second generation catalysts with 3-nitropropene. These stable complexes, formally ruthenaisoxazole N-oxide derivatives, display activity in both metathesis and non-metathetic processes such as cycloisomerisation, isomerisation and transfer hydrogenation.
Hydrazone and Oxime Olefination via Ruthenium Alkylidenes
作者:Daniel J. Nasrallah、Troy E. Zehnder、Jacob R. Ludwig、Daniel C. Steigerwald、John J. Kiernicki、Nathaniel K. Szymczak、Corinna S. Schindler
DOI:10.1002/anie.202112101
日期:2022.5.23
Olefination of carbon–heteroatom double bonds is a powerful approach to access highly functionalized olefins. An approach is reported here that uses air-stable and commercially available rutheniumalkylidenes to promote C=N/olefin ring closure. The enabling strategy for this reaction is the use of hydrazones and oximes as readily accessible substrates that preferentially react with ruthenium alkylidenes
Photoinduced Acylations Via Azolium-Promoted Intermolecular Hydrogen Atom Transfer
作者:Joshua L. Zhu、Cullen R. Schull、Anthony T. Tam、Ángel Rentería-Gómez、Achyut Ranjan Gogoi、Osvaldo Gutierrez、Karl A. Scheidt
DOI:10.1021/jacs.2c12845
日期:2023.1.25
Photoinduced hydrogenatomtransfer (HAT) has been developed as a powerful tool to generate synthetically valuable radical species. The direct photoexcitation of ketones has been known to promote HAT or to generate acyl radicals through Norrish-type pathways, but these modalities remain severely limited by radical side reactions. We report herein a catalyst- and transition metal-free method for the
光致氢原子转移 (HAT) 已被开发为生成具有合成价值的自由基物种的强大工具。已知酮的直接光激发可促进 HAT 或通过 Norrish 型途径产生酰基自由基,但这些方式仍然受到自由基副反应的严重限制。我们在此报告了一种无催化剂和过渡金属的 C-H 键酰化方法,该方法利用了稳定、可分离的酰基唑鎓物种的独特性质。具体而言,酰基唑盐显示在 LED 照射下会发生分子间和区域选择性 HAT,一系列底物带有活性 C-H 键,随后形成 C-C 键以提供酮。
pyridine-boronyl radical catalyzed intramolecular ring expansions. This metal-free radical pathway harnesses readily available catalysts and unactivated vinylcyclopropane starting materials, providing an array of cyclopentene derivatives chemoselectively under relatively mild conditions. Mechanistic studies support the idea that the boronyl radical engages in the generation of allylic/ketyl radical species
Intermolecular cross-carbonylation of aryl iodides with five-membered cyclic olefins such as dihydrofurans and cyclopentene was found to proceed by using a catalyst system of PdCl2/PPh(3) under CO (3-5 atm) in the presence of a tertiary amine. With 2,3- and 2,5-dihydrofurans, 2-aroyl-4,5-dihydro- and 3-aroyl-2,3-dihydrofurans were obtained as the predominant products, respectively, while the reaction of iodobenzene with cyclopentene gave a mixture of three regioisomers of benzoylcyclopentene. The yields of the products were observed to be markedly influenced by the amount of triphenylphosphine added.