Novel chiral thiourea organocatalysts for the catalytic asymmetric oxaziridination
摘要:
Catalytic enantioselective oxaziridination is one of the challenging reactions in the oxidation of organic molecules. In this article, a series of novel chiral thiourea moleculars were synthesized from natural cinchona alkaloids and primary amines. By using these molecules as organocatalysts and m-chloroper-oxybenzoicacid (m-CPBA) as the oxidant, a methodology on highly enantioselective epoxidation of al-dimines has been developed. Several optically active oxaziridines have been constructed in good yields (up to 95%) and moderate to excellent enantioselectivities (up to 99% ee). A plausible transition state was also proposed. (C) 2015 Elsevier Ltd. All rights reserved.
Branched Amine Synthesis via Aziridine or Azetidine Opening with Organotrifluoroborates by Cooperative Brønsted/Lewis Acid Catalysis: An Acid-Dependent Divergent Mechanism
作者:Truong N. Nguyen、Jeremy A. May
DOI:10.1021/acs.orglett.8b01394
日期:2018.6.15
A practical catalytic method to synthesize β,β- and γ,γ-substituted amines by opening aziridines and azetidines, respectively, using alkenyl, alkynyl, or aryl/heteroaryl trifluoroborate salts is described. This reaction features simple open-flask reaction conditions, the use of transition-metal-free catalysis, complete regioselectivity, and high diastereoselectivity. Preliminary mechanistic studies
Chiral‐Directing‐Group‐Assisted Rhodium(III)‐Catalyzed Asymmetric Addition of Inert Arene C−H Bond to Aldimines with Subsequent Intramolecular Cyclization
作者:Xuhong Cai、Wenkun Chen、Ruifang Nie、Jun Wang
DOI:10.1002/chem.202103319
日期:2021.12
An asymmetric rhodium(III)-catalyzed C−H bond addition to aldimines followed by subsequent intramolecular cyclization to form chiral isoindolinones has been achieved by using a chiral directing group. Various substituted benzamides and aldimines have been smoothly transformed to the corresponding products in up to 68 % yield with up to 93 % ee.
A nickel(0)‐catalyzed hydroalkenylation of imines with styrene and its derivatives is described. A wide range of aromatic and aliphatic imines directly coupled with styrene and its derivatives, thus providing various synthetically useful allylic amines with up to 95 % yield. The reaction offers a new atom‐ and step‐economical approach to allylic amines by using alkenes instead of alkenyl‐metallic reagents
N‐tosylarylimines and alkynes via ruthenium(II)‐catalyzed CH bond activation and annulation is described. The catalytic reaction proceeds well with a broad substrate scope and in good yields. A possible mechanism is proposed that involves imine nitrogen chelation‐assisted ortho‐CH bond activation of the substrate, alkyne insertion, and intramolecular insertion of the CN Ts group into the CRu bond. Isotope‐labeling
Pd/Al<sub>2</sub>O<sub>3</sub>-catalysed redox isomerisation of allyl alcohol: application in aldol condensation and oxidative heterocyclization reactions
作者:Dániel Zsolnai、Péter Mayer、Kornél Szőri、Gábor London
DOI:10.1039/c5cy01722j
日期:——
The application of the Pd/Al2O3 catalyst in allylalcohol isomerization and subsequent aldol condensation and heterocyclization reactions is described. The activity of Pd/Al2O3 in these transformations is suggested to be due to the participation of the Lewis acidic sites of the support in the activation of the alcohol towards oxidative dehydrogenation by the metal and subsequent hydride transfer. The
描述了Pd / Al 2 O 3催化剂在烯丙醇异构化以及随后的醛醇缩合和杂环化反应中的应用。Pd / Al 2 O 3的活性这些转化的推测是由于载体的路易斯酸性位点参与了醇向金属的氧化脱氢和随后的氢化物转移的活化。所得的烯醇(酸酯)/醛可能会因载体的酸碱性质而进一步发生反应。在异构化产物的醛醇缩合反应中,贫电子的芳族醛和杂芳族醛显示出最高的活性,而带有给电子取代基的芳族醛在转化为相应的N-甲苯磺酰基亚胺后反应。1,2-二取代的芳族化合物在一锅多步反应序列中得到杂环产物。