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1.
Jin‐Miao Tian Ai‐Fang Wang Ju‐Song Yang Xiao‐Jing Zhao Yong‐Qiang Tu Shu‐Yu Zhang Zhi‐Min Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11139-11143
A novel chiral 1,5‐N,N‐bidentate ligand based on a spirocyclic pyrrolidine oxazoline backbone was designed and prepared, and it coordinates CuBr in situ to form an unprecedented catalyst that enables efficient oxidative cross‐coupling of 2‐naphthols. Air serves as an external oxidant and generates a series of C1‐symmetric chiral BINOL derivatives with high enantioselectivity (up to 99 % ee) and good yield (up to 87 %). This approach is tolerant of a broader substrates scope, particularly substrates bearing various 3‐ and 3′‐substituents. A preliminary investigation using one of the obtained C1‐symmetric BINOL products was used as an organocatalyst, exhibiting better enantioselectivity than the previously reported organocatalyst, for the asymmetric α‐alkylation of amino esters. 相似文献
2.
Dong Xing Xiaotian Qi Daniel Marchant Peng Liu Guangbin Dong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4410-4414
Herein, we describe an intermolecular direct branched‐selective α‐alkylation of cyclic ketones with simple alkenes as the alkylation agents. Through an enamine‐transition metal cooperative catalysis mode, the α‐alkylation is realized in an atom‐ and step‐economic manner with excellent branched selectivity for preparing β‐branched ketones. Employment of a pair of bulky Brønsted acid and base as additives is responsible for enhanced efficiency. Promising enantioselectivity (74 % ee) has been obtained. Experimental and computational mechanistic studies suggest that a pathway through alkene migratory insertion into the Ir?C bond followed by C?H reductive elimination is involved for the high branched selectivity. 相似文献
3.
Umpolung Reactions of α‐Imino Esters: Useful Methods for the Preparation of α‐Amino Acid Frameworks 下载免费PDF全文
This paper summarizes our recent efforts toward the development of tandem reactions utilizing umpolung reactions of α‐imino esters. A highly diastereoselective tandem N‐alkylation–Mannich reaction of α‐imino esters was developed. A tandem N‐alkylation–addition reaction of α‐imino esters derived from ethyl glyoxylate with various aldehydes proceeded to give 1,2‐amino alcohols. The same reaction also proceeded efficiently using a novel flow system comprising two connected microreactors. Novel syntheses of α‐quaternary alkynyl amino esters and allenoates were developed through the use of umpolung N‐addition to β,γ‐alkynyl α‐imino esters, followed by regioselective acylation. In addition, a highly regioselective tandem N‐alkylation–vinylogous aldol reaction of β,γ‐alkenyl α‐imino esters was discovered. N‐Alkylation of α‐iminophosphonates followed by a Horner–Wadsworth–Emmons reaction with aldehydes occurred to afford enamines, which can be used in a four‐component coupling reaction with methyl vinyl ketone. α‐N‐Acyloxyimino esters served as highly efficient substrates for the N,N,C‐trialkylation reaction to introduce various nucleophiles at the imino nitrogen and carbon atoms. 相似文献
4.
Beln Rubial Beatrice S. L. Collins Raphael Bigler Stefan Aichhorn Adam Noble Varinder K. Aggarwal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1380-1384
The one‐pot sequential coupling of benzylamines, boronic esters, and aryl iodides has been investigated. In the presence of an N‐activator, the boronate complex formed from an ortho‐lithiated benzylamine and a boronic ester undergoes stereospecific 1,2‐metalate rearrangement/anti‐SN2′ elimination to form a dearomatized tertiary boronic ester. Treatment with an aryl iodide under palladium catalysis leads to rearomatizing γ‐selective allylic Suzuki–Miyaura cross‐coupling to generate 1,1‐diarylalkanes. When enantioenriched α‐substituted benzylamines are employed, the corresponding 1,1‐diarylalkanes are formed with high stereospecificity. 相似文献
5.
Highly Enantioselective Formation of α‐Allyl‐α‐Arylcyclopentanones via Pd‐Catalysed Decarboxylative Asymmetric Allylic Alkylation 下载免费PDF全文
Dr. Ramulu Akula Dr. Robert Doran Prof. Patrick J. Guiry 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9938-9942
A highly enantioselective Pd‐catalysed decarboxylative asymmetric allylic alkylation of cyclopentanone derived α‐aryl‐β‐keto esters employing the (R,R)‐ANDEN‐phenyl Trost ligand has been developed. The product (S)‐α‐allyl‐α‐arylcyclopentanones were obtained in excellent yields and enantioselectivities (up to >99.9 % ee). This represents one of the most highly enantioselective formations of an all‐carbon quaternary stereogenic center reported to date. This reaction was demonstrated on a 4.0 mmol scale without any deterioration of enantioselectivity and was exploited as the key enantioselective transformation in an asymmetric formal synthesis of the natural product (+)‐tanikolide. 相似文献
6.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(40):12480-12484
An unprecedented enantioselective allylic alkylation of readily available aldimine esters has been developed, and is catalyzed by a synergistic Cu/Pd catalyst system. This strategy provides facile access to nonproteinogenic α,α‐disubstituted α‐amino acids in high yield with excellent enantioselectivity. The more challenging double allylic alkylation of glycinate‐derived imine esters was also realized. Furthermore, this methodology was applied for the construction of the key intermediate of PLG peptidomimetics. 相似文献
7.
Fang Zhou Yao Zhang Xianfeng Xu Shaolin Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1768-1772
Reported here is a terminal‐selective, remote asymmetric hydroalkylation of olefins with racemic α‐bromo amides. The reaction proceeds by NiH‐catalyzed alkene isomerization and subsequent alkylation reaction, and can enantioconvergently introduce an unsymmetrical secondary alkyl group from a racemic α‐bromo amide onto a terminal C(sp3)?H position along the hydrocarbon chain of the alkene. This mild process affords a range of structurally diverse chiral α‐alkylalkanoic amides in excellent yields, and high regio‐ and enantioselectivities. In addition, the synthetic utility of this protocol is further highlighted by the regioconvergent conversion of industrial raw materials of isomeric olefin mixtures into enantioriched α‐alkylalkanoic amides on large scale. 相似文献
8.
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(38):11703-11706
The first highly enantioselective iridium‐catalyzed allylic alkylation that provides access to products bearing an allylic all‐carbon quaternary stereogenic center has been developed. The reaction utilizes a masked acyl cyanide (MAC) reagent, which enables the one‐pot preparation of α‐quaternary carboxylic acids, esters, and amides with a high degree of enantioselectivity. The utility of these products is further explored through a series of diverse product transformations. 相似文献
10.
Sri Krishna Nimmagadda Mingyu Liu Malkanthi K. Karunananda De‐Wei Gao Omar Apolinar Jason S. Chen Peng Liu Keary M. Engle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3963-3967
A palladium(II)‐catalyzed enantioselective α‐alkylation of azlactones with nonconjugated alkenes is described. The reaction employs a chiral BINOL‐derived phosphoric acid as the source of stereoinduction, and a cleavable bidentate directing group appended to the alkene to control the regioselectivity and stabilize the nucleopalladated alkylpalladium(II) intermediate in the catalytic cycle. A wide range of azlactones were found to be compatible under the optimal reaction conditions to afford products bearing α,α‐disubstituted α‐amino‐acid derivatives with high yields and high enantioselectivity. 相似文献
11.
Yiyang Liu Scott C. Virgil Robert H. Grubbs Brian M. Stoltz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(40):11966-11969
The direct α‐vinylation of carbonyl compounds to form a quaternary stereocenter is a challenging transformation. It was discovered that δ‐oxocarboxylic acids can serve as masked vinyl compounds and be unveiled by palladium‐catalyzed decarbonylative dehydration. The carboxylic acids are readily available through enantioselective acrylate addition or asymmetric allylic alkylation. A variety of α‐vinyl quaternary carbonyl compounds are obtained in good yields, and an application in the first enantioselective total synthesis of (−)‐aspewentins A, B, and C is demonstrated. 相似文献
12.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):10890-10894
α‐Amino nitriles tethered to alkenes through a urea linkage undergo intramolecular C‐alkenylation on treatment with base by attack of the lithionitrile derivatives on the N′‐alkenyl group. A geometry‐retentive alkene shift affords stereospecifically the E or Z isomer of the 5‐alkenyl‐4‐iminohydantoin products from the corresponding starting E ‐ or Z ‐N ′‐alkenyl urea, each of which may be formed from the same N ‐allyl precursor by stereodivergent alkene isomerization. The reaction, formally a nucleophilic substitution at an sp2 carbon atom, allows the direct regioselective incorporation of mono‐, di‐, tri‐, and tetrasubstituted olefins at the α‐carbon of amino acid derivatives. The initially formed 5‐alkenyl iminohydantoins may be hydrolyzed and oxidatively deprotected to yield hydantoins and unsaturated α‐quaternary amino acids. 相似文献
13.
Enantioselective Alkylation of N‐Arylhydrazones Derived from α‐Keto Esters and Isatin Derivatives through Asymmetric Phase‐Transfer Catalysis 下载免费PDF全文
Dr. Qi‐Kai Kang Dr. Sermadurai Selvakumar Prof. Dr. Natarajan Arumugam Prof. Dr. Abdulrahman I. Almansour Prof. Dr. Raju Suresh Kumar Prof. Dr. Keiji Maruoka 《化学:亚洲杂志》2018,13(14):1780-1783
The phase‐transfer‐catalyzed asymmetric alkylation reactions of N‐arylhydrazones derived from α‐keto‐esters and isatin derivatives afford enantioenriched azo compounds that bear a tetra‐substituted carbon stereocenter in good yields with high chemo‐ and enantioselectivity. The alkylation products can be readily converted into chiral amino esters, hydrazine derivatives, and aza‐β‐lactams without loss of enantiopurity. 相似文献
14.
Da Zhao Jiji Zhang Zuowei Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(47):13116-13120
o‐Carboryne can undergo α‐C H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes. 相似文献
15.
Taiki Hayashi Gerald Kehr Klaus Bergander Ryan Gilmour 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3854-3858
Sialic acids are ubiquitous components of mammalian cell membranes and key regulators of cellular recognition events. Located at the non‐reducing termini of bioactive gangliosides, these essential building blocks are fused to the polysaccharide core via a characteristic α‐linkage, and rarely occur in the monomeric form. Effective chemical strategies to enable α‐sialylation are urgently required to construct well‐defined tools for glycomics. To complement existing chemoenzymatic strategies, an α‐selective process has been devised based on the site‐selective introduction of fluorine at C3 (more than 20 examples, up to 90 % yield). Predicated on localized particle charge inversion (C?Hδ+→C?Fδ?), fluorine insertion simultaneously augments the anomeric effect, enhances electrophilicity at C2 and mitigates elimination. A stereochemical induction model is postulated that spans the SN continuum and validates the role of the C?F bond in orchestrating α‐selectivity. 相似文献
16.
Daniel Clare Benjamin C. Dobson Phillip A. Inglesby Christophe Aïssa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16344-16348
The functionalization of aryl and heteroaryls using α‐carbonyl sulfoxonium ylides without the help of a directing group has remained so far a neglected area, despite the advantageous safety profile of sulfoxonium ylides. Described herein are the cyclizations of α‐carbonyl sulfoxonium ylides onto benzenes, benzofurans and N‐p‐toluenesulfonyl indoles in the presence of a base in HFIP, whereas pyrroles and N‐methyl indoles undergo cyclization in the presence of an iridium catalyst. Significantly, these two sets of conditions are chemospecific for each groups of substrates. 相似文献
17.
Timothy B. Wright Ben W. H. Turnbull P. Andrew Evans 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9991-9995
An enantioselective rhodium‐catalyzed allylic alkylation of β,γ‐unsaturated α‐amino nitriles is described. This protocol provides a novel approach for the construction of β‐stereogenic carbonyl derivatives via the catalytic asymmetric alkylation of a homoenolate equivalent. The particularly challenging nature of this transformation is highlighted by the fact that three modes of selectivity must be manipulated, namely regio‐ and enantioselectivity, in addition to geometrical control. The γ‐stereogenic cyanoenamine products can be readily hydrolyzed in situ to afford the β‐substituted carboxylic acids, which in turn provide expedient access to a number of related carbonyl derivatives. Additionally, control experiments indicate that the chiral rhodium‐allyl intermediate facilitates the selective formation of the E‐cyanoenamine products, which is critical since the Z‐isomer affords significantly lower enantiocontrol. 相似文献
18.
Michael Z. Liang Simon J. Meek 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14372-14377
A catalytic enantioselective method for the synthesis of 1,4‐keto‐alkenylboronate esters by a rhodium‐catalyzed conjugate addition pathway is disclosed. A variety of novel, bench‐stable alkenyl gem‐diboronate esters are synthesized. These easily accessible reagents react smoothly with a collection of cyclic α,β‐unsaturated ketones, generating a new C?C bond and stereocenter. Products are isolated in up to 99 % yield with greater than 20:1 E/Z and greater than 99:1 e.r. Mechanistic studies show the site‐selectivity of transmetalation and reactivity is ligand dependent. The utility of the approach is highlighted by gram‐scale synthesis of enantioenriched cyclic 1,4‐diketones, and stereoselective transformations of the products by hydrogenation, allylation, and isomerization. 相似文献
19.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(4):1075-1078
Strecker synthesis has long been considered one of the prebiotic reactions for the synthesis of α‐amino acids. However, the correlation between the origin of chirality and highly enantioenriched α‐amino acids through this method remains a puzzle. In the reaction, it may be conceivable that the handedness of amino acids has been determined at the formation stage of the chiral intermediate α‐aminonitrile, that is, the enantioselective addition of hydrogen cyanide to an imine. Herein, an enantiotopic crystal surface of an achiral imine acted as an origin of chirality for the enantioselective formation of α‐aminonitriles by the addition of HCN. In conjunction with the amplification of the enantiomeric excess and multiplication of enantioenriched aminonitrile, a large amount of near enantiopure α‐amino acids, with the l ‐ and d ‐handedness corresponding to the molecular orientation of the imine, is reported. 相似文献
20.
Saravanakumar Elangovan Dr. Jean‐Baptiste Sortais Prof. Dr. Matthias Beller Prof. Dr. Christophe Darcel 《Angewandte Chemie (International ed. in English)》2015,54(48):14483-14486
A general and benign iron‐catalyzed α‐alkylation reaction of ketones with primary alcohols has been developed. The key to success of the reaction is the use of a Knölker‐type complex as catalyst (2 mol %) in the presence of Cs2CO3 as base (10 mol %) under hydrogen‐borrowing conditions. Using 2‐aminobenzyl alcohol as alkylation reagent allows for the “green” synthesis of quinoline derivatives. 相似文献