general, and functional group tolerant intramolecular hydroalkoxylation and hydroacyloxylation of unactivated olefins using a Co(salen) complex, an N-fluoropyridinium salt, and a disiloxane reagent is described. This reaction was carried out at room temperature and afforded five- and six-membered oxygen heterocyclic compounds, such as cyclic ethers and lactones. The Co complex was optimized for previously
描述了使用 Co(salen) 配合物、N-氟吡啶鎓盐和二硅氧烷试剂对未活化烯烃进行温和、通用和官能团耐受的分子内加氢烷氧基化和加氢酰氧基化。该反应在室温下进行,得到五元和六元氧杂环化合物,如环醚和内酯。通过未活化烯烃的加氢官能化,Co 配合物针对先前稀有介质环的形成进行了优化。强大的 Co 催化剂体系还可以使 O-保护的链烯醇脱保护加氢烷氧基化和链烯基酯加氢酰氧基化,直接得到环醚和内酯。研究了脱保护的底物范围和机理证明。
On the choice of Lewis acids for the Prins reaction; two total syntheses of (±)-Civet
作者:Freda K. Chio、Julie Warne、Damien Gough、Mark Penny、Sasa Green (née Martinović)、Simon J. Coles、Mike B. Hursthouse、Peter Jones、Lorraine Hassall、Thomas M. McGuire、Adrian P. Dobbs
DOI:10.1016/j.tet.2011.05.019
日期:2011.7
While developing new variations of the Prins cyclisation reaction, the effect of the choice of Lewis acid on the outcome of the reaction and the product(s) has been investigated, yielding hitherto unseen dihydropyran products in the Prins cyclisation reaction of homoallylic alcohols, and two new modifications of the reaction: the triflate-trapped Prins adduct and the Mukaiyama-Aldol-silyl-Prins reaction. Two of these methods are employed in two complementary total syntheses of the important perfumery compound, (+/-)-Civet. (C) 2011 Elsevier Ltd. All rights reserved.
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。