Methods for the synthesis of chiral sulfur heterocycles and their application in the asymmetric Baylis–Hillman reactions
摘要:
Enantiomerically pure (2S,6S)-2,6-diphenyltetrahydro-2H-thiopyran, (2S)-2-phenyltetrahydro thiophene, and (2S)-2-phenyltetrahydro-2H-thiopyran were prepared in 70-72% yields and with 86-99% ee via cyclization of the corresponding dimesylate in an S(N)2 cyclization reaction using sodium sulfide nonahydrate. The results on the application of various chiral sulfides in asymmetric Baylis-Hillman reactions are also described. (C) 2013 Elsevier Ltd. All rights reserved.
Methods for the synthesis of chiral sulfur heterocycles and their application in the asymmetric Baylis–Hillman reactions
摘要:
Enantiomerically pure (2S,6S)-2,6-diphenyltetrahydro-2H-thiopyran, (2S)-2-phenyltetrahydro thiophene, and (2S)-2-phenyltetrahydro-2H-thiopyran were prepared in 70-72% yields and with 86-99% ee via cyclization of the corresponding dimesylate in an S(N)2 cyclization reaction using sodium sulfide nonahydrate. The results on the application of various chiral sulfides in asymmetric Baylis-Hillman reactions are also described. (C) 2013 Elsevier Ltd. All rights reserved.
Enantioselective Radical Cyclization for Construction of 5-Membered Ring Structures by Metalloradical C–H Alkylation
作者:Yong Wang、Xin Wen、Xin Cui、X. Peter Zhang
DOI:10.1021/jacs.8b01662
日期:2018.4.11
use of unsaturated substrates. Guided by the concept of metalloradicalcatalysis, a different mode of radical cyclization that can employ saturated C-H substrates is demonstrated through the development of a Co(II)-based system for catalytic activation of aliphatic diazo compounds for enantioselective radical alkylation of various C(sp3)-H bonds. It allows for efficient construction of chiral pyrrolidines
自由基环化代表了构建环状结构的强大策略。传统的自由基环化以自由基加成为关键步骤,需要使用不饱和底物。在金属自由基催化概念的指导下,通过开发基于Co(II)的系统,展示了一种可以使用饱和CH底物的不同自由基环化模式,该系统用于催化活化脂肪族重氮化合物,以实现各种C(sp3)的对映选择性自由基烷基化)-H键。它可以有效构建手性吡咯烷和其他有价值的五元环状化合物。这种自由基环化的替代策略提供了一种新的逆合成范例,通过 CH 和 C=O 元素的结合形成 CC 键,从容易获得的开链醛制备五元环状分子。
Brønsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
作者:Anon Bunrit、Christian Dahlstrand、Sandra K. Olsson、Pemikar Srifa、Genping Huang、Andreas Orthaber、Per J. R. Sjöberg、Srijit Biswas、Fahmi Himo、Joseph S. M. Samec
DOI:10.1021/jacs.5b02013
日期:2015.4.15
intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as
富含对映体的苄基、炔丙基、烯丙基和烷基醇的羟基已被不带电荷的 O-、N-和 S 中心亲核试剂在分子内置换,在次膦酸催化下产生富含对映体的四氢呋喃、吡咯烷和四氢噻吩衍生物。五元杂环产物的产率很高,手性转移程度高,水是唯一的副产物。消旋化实验表明次膦酸不会促进 SN1 反应性。密度泛函理论计算证实了一种反应途径,其中次膦酸在分子内取代反应中充当双功能催化剂。在该机制中,次膦酸的酸质子使羟基质子化,从而增强离去基团能力。同时地,次膦酸的氧代基团作为碱提取亲核质子,从而增强亲核性。该反应将开辟新的原子高效技术,使醇在未来能够在取代反应中用作核离剂。
Phosphorothioic Acids and Related Compounds as Surrogates for H<sub>2</sub>S—Synthesis of Chiral Tetrahydrothiophenes
作者:Forest J. Robertson、Jimmy Wu
DOI:10.1021/ja210758n
日期:2012.2.8
The convenient preparation of chiral tetrahydrothiophenes (THTs) in high enantiopurity via phosphorothioic acids and relatedcompounds is reported. We consider these to be safer alternatives to the use of H(2)S which is a highly toxic gas. Each of the THTs is derivedfrom a common intermediate, thereby greatly enhancing the flexibility of the synthesis. The key transformation is a base-promoted, intramolecular
Methods for the synthesis of chiral sulfur heterocycles and their application in the asymmetric Baylis–Hillman reactions
作者:Mariappan Periasamy、Ramani Gurubrahamam、Gopal P. Muthukumaragopal
DOI:10.1016/j.tetasy.2013.03.021
日期:2013.5
Enantiomerically pure (2S,6S)-2,6-diphenyltetrahydro-2H-thiopyran, (2S)-2-phenyltetrahydro thiophene, and (2S)-2-phenyltetrahydro-2H-thiopyran were prepared in 70-72% yields and with 86-99% ee via cyclization of the corresponding dimesylate in an S(N)2 cyclization reaction using sodium sulfide nonahydrate. The results on the application of various chiral sulfides in asymmetric Baylis-Hillman reactions are also described. (C) 2013 Elsevier Ltd. All rights reserved.