Asymmetric Synthesis of Nonracemic Primary Amines via Spiroborate-Catalyzed Reduction of Pure (<i>E</i>)- and (<i>Z</i>)-<i>O</i>-Benzyloximes: Applications toward the Synthesis of Calcimimetic Agents
作者:Wenhua Ou、Sandraliz Espinosa、Héctor J. Meléndez、Silvia M. Farré、Jaime L. Alvarez、Valerie Torres、Ileanne Martínez、Kiara M. Santiago、Margarita Ortiz-Marciales
DOI:10.1021/jo400371x
日期:2013.6.7
Highly enantiopure (1-aryl)- and (1-naphthyl)-1-ethylamines were synthesized by the borane-mediated reduction of single-isomeric (E)- and (Z)-O-benzyloxime ethers using the stable spiroborate ester derived from (S)-diphenyl valinol and ethylene glycol as the chiral catalyst. Primary (R)-arylethylamines were prepared by the reduction of pure (Z)-ethanone oxime ethers in up to 99% ee using 15% of catalyst
使用衍生自稳定的螺硼酸酯,通过硼烷介导的单一异构体 ( E )- 和 ( Z ) -O-苄基肟醚的还原,合成了高对映体纯的 (1-芳基)-和 (1-萘基)-1-乙胺( S )-二苯基缬氨醇和乙二醇作为手性催化剂。伯 ( R )-芳基乙胺是通过使用 15% 的催化剂将纯 ( Z )-乙酮肟醚还原至 99% ee来制备的。描述了使用对映纯(1-萘-1-基)乙胺作为手性前体合成新的和已知的拟钙剂类似物的两种方便且容易的方法。
Cobalt-Catalyzed Aerobic Oxidative C–H/C–H Cross-Coupling of Unactivated Arenes for the Synthesis of Biaryls
A mild and efficient protocol for the synthesis of 2,2′-difunctional biaryls from readily available benzamides and oximes by Co(OAc)2·4H2O catalysis has been developed. The catalytic cycle that includes aerobic oxidation of Co(I) to Co(III) is successfully achieved for the first time through dual-chelation-assisted C–H/C–H coupling with the assistance of catalytic Mn(acac)3. The catalytic system exhibits
A novel protocol for the activation of the Beckmannrearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol %) has been developed. A unique self-propagating mechanism for the substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol
Cp*-Free Cobalt-Catalyzed C–H Activation/Annulations by Traceless <i>N</i>,<i>O</i>-Bidentate Directing Group: Access to Isoquinolines
作者:Xiao-Cai Li、Cong Du、He Zhang、Jun-Long Niu、Mao-Ping Song
DOI:10.1021/acs.orglett.9b00866
日期:2019.4.19
N,O-Bidentate directing-enabled, traceless heterocycle synthesis is described via Cp*-free cobalt-catalyzedC–Hactivation/annulation. The weakly coordinating nature of the carboxylic acid was employed for the preparation of isoquinolines. Meanwhile, the N–Obond of the α-imino-oxy acid can serve as an internaloxidant. Terminal as well as internalalkynes can be efficiently applied to the catalytic
o-Phthalic Anhydride/Zn(OTf)2 co-catalyzed Beckmann rearrangement under mild conditions
作者:Ze-Feng Xu、Teng Zhang、Wenjun Hong
DOI:10.1016/j.tet.2019.04.056
日期:2019.6
o-Phthalic anhydride/Zn(OTf)2 co-catalyzed Beckmann rearrangement was developed, producing the corresponding amide in up to 99% yield with acid-sensitive functionalities tolerated well, and the scale of the reaction could be enlarged to 77 mmol and the excellent yield was maintained. A successive procedure was developed. Moreover, the reaction was carried out at rt under nearly neutral conditions,