共查询到20条相似文献,搜索用时 15 毫秒
1.
Dr. Bo Peng Dr. Xueliang Huang Dr. Lan‐Gui Xie Prof. Dr. Nuno Maulide 《Angewandte Chemie (International ed. in English)》2014,53(33):8718-8721
A Brønsted acid catalyzed redox arylation of ynamides that employs aryl sulfoxides as the arylating agents is reported. This metal‐free transformation proceeds at room temperature and efficiently affords α‐arylated oxazolidinones in a redox‐neutral, atom‐economic fashion. 相似文献
2.
3.
Brønsted Acid Catalyzed Asymmetric Hydroamination of Alkenes: Synthesis of Pyrrolidines Bearing a Tetrasubstituted Carbon Stereocenter 下载免费PDF全文
Dr. Jin‐Shun Lin Peng Yu Lin Huang Pan Zhang Prof. Dr. Bin Tan Prof. Dr. Xin‐Yuan Liu 《Angewandte Chemie (International ed. in English)》2015,54(27):7847-7851
The first highly enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes enables the efficient construction of a series of chiral (spirocyclic) pyrrolidines with an α‐tetrasubstituted carbon stereocenter with excellent functional group tolerance. A unique feature of this strategy is the use of a thiourea group acting as both the activating and the directing group through cooperative multiple hydrogen bonding with a Brønsted acid and the double bond. The utility of this method is highlighted by the facile construction of chiral synthetic intermediates and important structural motifs that are widely found in organic synthesis. 相似文献
4.
5.
Kai Yang Yixian Lou Chenglan Wang Liang‐Wen Qi Tongchang Fang Feng Zhang Hetao Xu Lu Zhou Wangyang Li Guan Zhang Peiyuan Yu Qiuling Song 《Angewandte Chemie (International ed. in English)》2020,59(8):3294-3299
A new chiral Brønsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This “designer acid catalyst”, which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2‐aryl‐substituted N‐unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3‐protonation and hydride‐transfer processes. Besides, bulky C2‐alkyl‐substituted N‐unprotected indoles are also suitable for this system. 相似文献
6.
Estela Álvarez Dr. Olalla Nieto Faza Dr. Carlos Silva López Dr. Manuel A. Fernández‐Rodríguez Prof. Dr. Roberto Sanz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):12889-12893
A cascade reaction of indoles with propargylic diols involving an unprecedented metal‐free 1,2‐indole migration onto an alkyne was carried out. DFT calculations support a mechanism consisting of a concerted nucleophilic attack of the indole nucleus with loss of water, followed by the 1,2‐migration and subsequent Nazarov cyclization. This Brønsted acid‐catalyzed protocol affords indole‐functionalized benzofulvene derivatives in high yields. 相似文献
7.
Salicylato Titanocene Complexes as Cooperative Organometallic Lewis Acid and Brønsted Acid Catalysts for Three‐Component Mannich Reactions 下载免费PDF全文
Dr. Ya Wu Chun Chen Gai Jia Xuyang Zhu Dr. Huaming Sun Prof. Guofang Zhang Prof. Weiqiang Zhang Prof. Ziwei Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8530-8535
A binary acid system has been developed that features an air‐stable organometallic precursor, titanocene dichloride, and simple organic cooperative Brønsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including 1H NMR titration, X‐ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system. 相似文献
8.
Dr. Weijun Tang Steven Johnston Dr. Chaoqun Li Dr. Jonathan A. Iggo Dr. John Bacsa Prof. Jianliang Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14187-14193
Asymmetric hydrogenation of imines leads directly to chiral amines, one of the most important structural units in chemical products, from pharmaceuticals to materials. However, highly effective catalysts are rare. This article reveals that combining an achiral pentamethylcyclopentadienyl (Cp*)–iridium complex with a chiral phosphoric acid affords a catalyst that allows for highly enantioselective hydrogenation of imines derived from aryl ketones, as well as those derived from aliphatic ones, with ee values varying from 81 to 98 %. A range of achiral iridium complexes containing diamine ligands were examined, for which the ligands were shown to have a profound effect on the reaction rate, enantioselectivity and catalyst deactivation. The chiral phosphoric acid is no less important, inducing enantioselection in the hydrogenation. The induction occurs, however, at the expense of the reaction rate. 相似文献
9.
Tetiana Krachko Volodymyr Lyaskovskyy Martin Lutz Koop Lammertsma J. Chris Slootweg 《无机化学与普通化学杂志》2017,643(14):916-921
Recently, Brønsted acids, such as phosphoric acids, carboxylic acids, and triflic acid, were found to catalyze the reduction of phosphine oxides to the corresponding phosphines. In this study, we fully characterize the HCl, HOTf, and Me2SiHOTf adducts of triphenylphosphine oxide and find that the thermally stable adduct Ph3POH+OTf– is efficiently converted into triphenylphosphine at 100 °C in the presence of readily available hydrosiloxanes. Under the same reaction conditions, also Ph3POSiMe2H+OTf– selectively affords triphenylphosphine indicating that silylated phosphine oxides are likely intermediates in this process. 相似文献
10.
11.
12.
13.
Kinetic Resolution of Azomethine Imines by Brønsted Acid Catalyzed Enantioselective Reduction 下载免费PDF全文
Amanda Bongers Patrick J. Moon Prof. Dr. André M. Beauchemin 《Angewandte Chemie (International ed. in English)》2015,54(51):15516-15519
Azomethine imines are valuable substrates in asymmetric catalysis, and can be precursors to β‐amino carbonyl compounds and complex hydrazines. However, their utility is limited because complex and enantioenriched azomethine imines are often unavailable. Reported herein is a kinetic resolution of N,N′‐cyclic azomethine imines by enantioselective reduction (s=13–43). This resolution was accomplished using a Brønsted acid catalyst, and represents the first example of the asymmetric reduction of azomethine imines. The pyrazolidinone product (up to 86 % ee) and the recovered azomethine imine (up to 99 % ee) can both be used to access the opposite enantiomers of valuable products. 相似文献
14.
Liwen Fan Chunyu Han Xuerong Li Jiasheng Yao Zhengning Wang Chaochao Yao Weihao Chen Prof. Dr. Tao Wang Prof. Dr. Junfeng Zhao 《Angewandte Chemie (International ed. in English)》2018,57(8):2115-2119
The first enantioselective polyene cyclization initiated by a BINOL‐derived chiral N‐phosphoramide (NPA) catalyzed protonation of an imine is described. The ion‐pair formed between the iminium ion and chiral counter anion of the NPA plays an important role for controlling the stereochemistry of the overall transformation. This strategy offers a highly efficient approach to fused tricyclic frameworks containing three contiguous stereocenters, which are widely found in natural products. In addition, the first catalytic asymmetric total synthesis of (?)‐ferruginol was accomplished with an NPA catalyzed enantioselective polyene cyclization, as the key step for the construction of the tricyclic core, with excellent yield and enantioselectivity. 相似文献
15.
16.
Sandra Rodriguez Uxue Uria Efraim Reyes Luisa Carrillo Toms Tejero Pedro Merino Jose L. Vicario 《Angewandte Chemie (International ed. in English)》2020,59(17):6780-6784
The enantioselective synthesis of tropanols has been accomplished through chiral phosphoric acid catalyzed pseudotransannular ring opening of 1‐aminocyclohept‐4‐ene‐derived epoxides. The reaction proceeds together with the desymmetrization of the starting material and leads to the direct formation of the 8‐azabicyclo[3.2.1]octane scaffold with excellent stereoselectivity. The synthetic applicability of the reaction was demonstrated by the enantioselective synthesis of the two natural products (?)‐α‐tropanol and (+)‐ferruginine. 相似文献
17.
Waqar Ahmed Sheng Zhang Xiaoqiang Yu Xiujuan Feng Yoshinori Yamamoto Ming Bao 《Angewandte Chemie (International ed. in English)》2019,58(8):2495-2499
The cooperative catalysis of copper, silver, and Brønsted acid is presented as a new strategy for olefin functionalization. The catalytic direct carbohydroxylation of arylalkenes with allylic alcohols provided a straightforward and efficient approach for preparing 4,5‐unsaturated alcohols. Synthetically useful functional groups, such as Cl, Br, carbonyl, and chloromethyl, remained intact during the functionalization reaction. 相似文献
18.
19.
20.
Highly Enantioselective Kinetic Resolution of Axially Chiral BINAM Derivatives Catalyzed by a Brønsted Acid 下载免费PDF全文
Dr. Dao‐Juan Cheng Liang Yan Prof. Dr. Shi‐Kai Tian Ming‐Yue Wu Lu‐Xin Wang Zi‐Li Fan Dr. Sheng‐Cai Zheng Prof. Dr. Xin‐Yuan Liu Prof. Dr. Bin Tan 《Angewandte Chemie (International ed. in English)》2014,53(14):3684-3687
A highly efficient strategy for the kinetic resolution of axially chiral BINAM derivatives involving a chiral Brønsted acid‐catalyzed imine formation and transfer hydrogenation cascade process was developed. The kinetic resolution provides a convenient route to chiral BINAM derivatives in high yields with excellent enantioselectivities. 相似文献