Controllable, Sequential, and Stereoselective C–H Allylic Alkylation of Alkenes
作者:Ling Qin、Mohammed Sharique、Uttam K. Tambar
DOI:10.1021/jacs.9b08801
日期:2019.10.30
new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylicposition of propylene and other simple terminal
将 CH 键直接转化为新的 CC 键代表了一种从简单的起始材料生成复杂分子的强大方法。然而,将甲基顺序转化为完全取代的碳中心的通用且可控的方法仍然是一个挑战。我们报告了一种新方法,用于选择性和顺序替换丙烯和其他简单末端烯烃的烯丙基位置的三个 CH 键,该烯烃具有源自格氏试剂的不同碳基团。铜催化剂和富电子联芳膦配体有助于以高支链选择性形成烯丙基烷基化产物。我们还提出了在催化铜和手性膦配体存在下生成对映体富集的烯丙基烷基化产物的条件。通过这种方法,
Urea as a Redox-Active Directing Group under Asymmetric Photocatalysis of Iridium-Chiral Borate Ion Pairs
diastereo- and enantioselective [3 + 2]-cycloaddition of N-cyclopropylurea with α-alkylstyrenes is reported. This asymmetric radical cycloaddition relies on the strategic placement of urea on cyclopropylamine as a redox-active directing group (DG) with anion-binding ability and the use of an ion pair, comprising an iridium polypyridyl complex and a weakly coordinating chiral borate ion, as a photocatalyst
a suitable photosensitizer, which enables precise modulation of sulfenamides by promoting unprecedented energy transfer rather than traditional single-electron oxidation. This novel strategy leads to the concurrent formation of N- and S-radical species, ensuring high regioselectivity for both electron-neutral and electron-deficient alkenes. As a result, a wide range of valuable β-amino sulfides, including
β-氨基硫化物具有重要的生物学意义,推动了烯烃亚磺胺化的几种方法的发展。然而,这些方法通常涉及烯烃底物范围有限的三组分系统。在这项研究中,我们提出了一种开创性的双组分方法,利用易于获得的次磺酰胺作为高效的双官能团化试剂。其成功的关键是精心选择合适的光敏剂,通过促进前所未有的能量转移而不是传统的单电子氧化,实现次磺酰胺的精确调制。这种新颖的策略导致 N 和 S 自由基物种的同时形成,确保对电子中性和缺电子烯烃的高区域选择性。因此,可以很容易地合成各种有价值的 β-氨基硫化物,包括那些具有拥挤胺基的硫化物。这些发现突出了该方法在高效合成多种官能化 β-氨基硫化物方面的潜力。
Intramolecular nucleophilic addition to unsaturated carbon. Dependence of cyclization efficiency on the method of carbon-carbon bond cleavage utilized to generate the reactive species
作者:Leo A. Paquette、John P. Gilday、George D. Maynard