[reaction: see text] New Lewis acid-assisted Bronsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimeticpolyenecyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1'R,2'R)-trans-2'-(3' ',5' '-xylyl)cyclohexanoxy]phenol gave a trans-fused tricyclic compound with 85% ee.
Asymmetric Induction via a Helically Chiral Anion: Enantioselective Pentacarboxycyclopentadiene Brønsted Acid-Catalyzed Inverse-Electron-Demand Diels–Alder Cycloaddition of Oxocarbenium Ions
作者:Chirag D. Gheewala、Jennifer S. Hirschi、Wai-Hang Lee、Daniel W. Paley、Mathew J. Vetticatt、Tristan H. Lambert
DOI:10.1021/jacs.8b00260
日期:2018.3.14
An enantioselective catalytic inverse-electron-demand Diels-Alder reaction of salicylaldehyde acetal-derived oxocarbenium ions and vinyl ethers to generate 2,4-dioxychromanes is described. Chiral pentacarboxycyclopentadiene (PCCP) acids are found to be effective for a variety of substrates. Computational and X-ray crystallographic analyses support the unique hypothesis that an anion with point-chirality-induced
描述了水杨醛缩醛衍生的氧代碳鎓离子和乙烯基醚的对映选择性催化逆电子需求 Diels-Alder 反应,以生成 2,4-二氧色满。发现手性五羧基环戊二烯 (PCCP) 酸对多种底物有效。计算和 X 射线晶体学分析支持独特的假设,即具有点手性诱导的螺旋手性的阴离子决定了该反应中立体化学的绝对意义。
Organolithium/Chiral Lewis Base/BF3: a Versatile Combination for the Enantioselective Desymmetrization ofmeso-Epoxides
BF3 can be used in combination with organolithium/strong Lewis base complexes for the enantioselective nucleophilic ring-opening or the carbenoidic rearrangement of various meso-oxiranes with excellent yields and ee values of up to 87 %. Mechanistic aspects of these reactions are considered.
Aryl lithium reagents, complexed with (-)-sparteine, react enantioselectively with cyclic meso epoxides, to afford chiral aryl cyclanols. The enantiomeric excess, though moderate (27-87%), is the best in the literature for such a reaction. Activation by BF3 · OEt2 is needed, and is compatible with a diamine such as (-)-sparteine.
Palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones for the synthesis of <i>trans</i> cycloalkanols through dynamic kinetic resolution under acidic conditions
The first efficient palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones has been described through dynamickineticresolution under acidic conditions, providing a facile access to chiral trans cycloalkanol derivatives with excellent enantioselectivities.