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1.
Synthesis of Branched‐Chain Sugars with a DHAP‐Dependent Aldolase: Ketones are Electrophile Substrates of Rhamnulose‐1‐phosphate Aldolases 下载免费PDF全文
Victor Laurent Dr. Ekaterina Darii Angelina Aujon Marine Debacker Jean‐Louis Petit Dr. Virgil Hélaine Dr. Tibor Liptaj Martin Breza Aline Mariage Lionel Nauton Dr. Mounir Traïkia Dr. Marcel Salanoubat Prof. Dr. Marielle Lemaire Dr. Christine Guérard‐Hélaine Dr. Véronique de Berardinis 《Angewandte Chemie (International ed. in English)》2018,57(19):5467-5471
Dihydroxyacetone phosphate (DHAP)‐dependent rhamnulose aldolases display an unprecedented versatility for ketones as electrophile substrates. We selected and characterized a rhamnulose aldolase from Bacteroides thetaiotaomicron (RhuABthet) to provide a proof of concept. DHAP was added as a nucleophile to several α‐hydroxylated ketones used as electrophiles. This aldol addition was stereoselective and produced branched‐chain monosaccharide adducts with a tertiary alcohol moiety. Several aldols were readily obtained in good to excellent yields (from 76 to 95 %). These results contradict the general view that aldehydes are the only electrophile substrates for DHAP‐dependent aldolases and provide a new C?C bond‐forming enzyme for stereoselective synthesis of tertiary alcohols. 相似文献
2.
Rhodium‐catalyzed Asymmetric Hydrogenation of α‐Dehydroamino Ketones: A General Approach to Chiral α‐amino Ketones 下载免费PDF全文
Rhodium/DuanPhos‐catalyzed asymmetric hydrogenation of aliphatic α‐dehydroamino ketones has been achieved and afforded chiral α‐amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β‐amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α‐amino ketones and chiral β‐amino alcohols. 相似文献
3.
Rhodium‐Catalyzed Ketone Methylation Using Methanol Under Mild Conditions: Formation of α‐Branched Products 下载免费PDF全文
Dr. Louis K. M. Chan Darren L. Poole Di Shen Dr. Mark P. Healy Prof. Timothy J. Donohoe 《Angewandte Chemie (International ed. in English)》2014,53(3):761-765
The rhodium‐catalyzed methylation of ketones has been accomplished using methanol as the methylating agent and the hydrogen‐borrowing method. The sequence is notable for the relatively low temperatures that are required and for the ability of the reaction system to form α‐branched products with ease. Doubly alkylated ketones can be prepared from methyl ketones and two different alcohols by using a sequential one‐pot iridium‐ and rhodium‐catalyzed process. 相似文献
4.
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
5.
Katharina Tauber Michael Fuchs Johann H. Sattler Julia Pitzer Desiree Pressnitz Dr. Dominik Koszelewski Prof. Kurt Faber Jan Pfeffer Thomas Haas Prof. Wolfgang Kroutil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):4030-4035
Various artificial network designs that involve biocatalysts were tested for the asymmetric amination of sec‐alcohols to the corresponding α‐chiral primary amines. The artificial systems tested involved three to five redox enzymes and were exemplary of a range of different sec‐alcohol substrates. Alcohols were oxidised to the corresponding ketone by an alcohol dehydrogenase. The ketones were subsequently aminated by employing a ω‐transaminase. Of special interest were redox‐neutral designs in which the hydride abstracted in the oxidation step was reused in the amination step of the cascade. Under optimised conditions up to 91 % conversion of an alcohol to the amine was achieved. 相似文献
6.
7.
Xiaoge Yang Zhuqing Liu Prof. Chenglin Sun Prof. Dr. Jiping Chen Prof. Dr. Zhengkun Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14085-14094
Efficient palladium‐catalyzed cross‐coupling reactions of the internal olefins α‐cyanoketene dithioacetals with a variety of olefins were achieved in dioxane/HOAc/DMSO (9:3:1 v/v/v) under air atmosphere or by means of AgOAc as the terminal oxidant. Electron‐deficient terminal olefins reacted to form the linear diene derivatives with air as the oxidant. Styrenes underwent the cross‐coupling to give both the linear and branched dienes when using AgOAc as the oxidant. Unactivated cyclic and linear internal olefin substrates both reacted in the presence of a catalytic amount of benzoquinone in air to produce skipped dienes. The typical products were structurally confirmed by X‐ray crystallography. 相似文献
8.
Design of New Ligands for the Palladium‐Catalyzed Arylation of α‐Branched Secondary Amines 下载免费PDF全文
Nathaniel H. Park Ekaterina V. Vinogradova Dr. David S. Surry Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (International ed. in English)》2015,54(28):8259-8262
In Pd‐catalyzed C? N cross‐coupling reactions, α‐branched secondary amines are difficult coupling partners and the desired products are often produced in low yields. In order to provide a robust method for accessing N‐aryl α‐branched tertiary amines, new catalysts have been designed to suppress undesired side reactions often encountered when these amine nucleophiles are used. These advances enabled the arylation of a wide array of sterically encumbered amines, highlighting the importance of rational ligand design in facilitating challenging Pd‐catalyzed cross‐coupling reactions. 相似文献
9.
Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (International ed. in English)》2020,59(40):17641-17647
Catalytic enantioselective α‐fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α‐fluorinated carbonyl compounds. Nevertheless, α‐fluorination of α‐nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α‐hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3‐(2‐naphthyl)‐l ‐alanine‐derived amides are highly effective catalysts for the enantio‐ and site‐selective α‐fluorination of N‐(α‐arylacetyl) and N‐(α‐alkylacetyl) 3,5‐dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α‐fluorinated α‐amino acid derivative). α‐Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield. 相似文献
10.
Copper‐Catalyzed Borylative Cross‐Coupling of Allenes and Imines: Selective Three‐Component Assembly of Branched Homoallyl Amines 下载免费PDF全文
Dr. James Rae Kay Yeung Dr. Joseph J. W. McDouall Prof. Dr. David J. Procter 《Angewandte Chemie (International ed. in English)》2016,55(3):1102-1107
A copper‐catalyzed three‐component coupling of allenes, bis(pinacolato)diboron, and imines allows regio‐, chemo‐, and diastereoselective assembly of branched α,β‐substituted‐γ‐boryl homoallylic amines, that is, products bearing versatile amino, alkenyl, and borane functionality. Alternatively, convenient oxidative workup allows access to α‐substituted‐β‐amino ketones. A computational study has been used to probe the stereochemical course of the cross‐coupling. 相似文献
11.
Substrate‐Directed Hydroacylation: Rhodium‐Catalyzed Coupling of Vinylphenols and Nonchelating Aldehydes 下载免费PDF全文
Stephen K. Murphy Dr. Achim Bruch Dr. Vy M. Dong 《Angewandte Chemie (International ed. in English)》2014,53(9):2455-2459
We report a protocol for the hydroacylation of vinylphenols with aryl, alkenyl, and alkyl aldehydes to form branched products with high selectivity. This cross‐coupling yields α‐aryl ketones that can be cyclized to benzofurans, and it enables access to eupomatenoid natural products in four steps or less from eugenol. Excellent reactivity and high levels of regioselectivity for the formation of the branched products were observed. We propose that aldehyde decarbonylation is avoided by the use of an anionic directing group on the alkene and a diphosphine ligand with a small bite angle. 相似文献
12.
Ligand‐free Pd/Cu‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates 下载免费PDF全文
This paper describes a palladium/copper‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates. The cross‐coupling reaction gives high chemical yields of aryl ketones and has wide functional group tolerance, making the transformation an attractive alternative to the traditional cross‐coupling approaches for aryl ketones. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation 下载免费PDF全文
Fei Huang Zhuqing Liu Prof. Dr. Zhengkun Yu 《Angewandte Chemie (International ed. in English)》2016,55(3):862-875
Transition‐metal‐catalyzed C‐alkylation of ketones and secondary alcohols, with alcohols, avoids use of organometallic or environmentally unfriendly alkylating agents by means of borrowing hydrogen (BH) or hydrogen autotransfer (HA) activation of the alcohol substrates. Water is formed as the only by‐product, thus making the BH process atom‐economical and environmentally benign. Diverse homogeneous and heterogeneous transition‐metal catalysts, ketones, and alcohols can be used for this transformation, thus rendering the BH process promising for replacing those procedures that use traditional alkylating agents. This Minireview summarizes the advances during the last five years in transition‐metal‐catalyzed BH α‐alkylation of ketones, and β‐alkylation of secondary alcohols with alcohols. A discussion on the application of the BH strategy for C?C bond formation is included. 相似文献
14.
Starting with the N‐substituted anilines 4/12 and the α‐branched ketones 3 the 3H‐indolium salts 1 and their fused derivatives 13 are prepared by combining a sodium nitrite nitrosation, a zinc dust reduction, a hydrazone formation and a Fischer indolization to a reaction sequence in which the isolation and purification of intermediates is not necessary. The scope and limitations of this effective one‐pot synthesis are discussed. 相似文献
15.
Catalyst‐Free Dehydrative α‐Alkylation of Ketones with Alcohols: Green and Selective Autocatalyzed Synthesis of Alcohols and Ketones 下载免费PDF全文
Prof. Dr. Qing Xu Jianhui Chen Haiwen Tian Xueqin Yuan Shuangyan Li Chongkuan Zhou Dr. Jianping Liu 《Angewandte Chemie (International ed. in English)》2014,53(1):225-229
Direct dehydrative α‐alkylation reactions of ketones with alcohols are now realized under simple, practical, and green conditions without using external catalysts. These catalyst‐free autocatalyzed alkylation methods can efficiently afford useful alkylated ketone or alcohol products in a one‐pot manner and on a large scale by C?C bond formation of the in situ generated intermediates with subsequent controllable and selective Meerwein–Pondorf–Verley–Oppenauer‐type redox processes. 相似文献
16.
《应用有机金属化学》2017,31(3)
Polystyrene‐supported N ,N ‐dimethylethylenediamine Pd(II) complex C was used as an efficient catalyst for the synthesis of aromatic ketones via ortho ‐acylation of sp2 C─H bonds of 2‐arylpyridines with alcohols as effective coupling partners. The alcohols were oxidized with tert ‐butyl hydroperoxide to their corresponding aldehydes in situ and efficiently coupled with 2‐arylpyridines to form aryl ketones under solvent‐free conditions. Furthermore, catalyst C could be easily recovered by simple filtration and reused for five cycles without any significant decrease in its activity. 相似文献
17.
Jiang Wang Brian P. Cary Peyton D. Beyer Samuel H. Gellman Daniel J. Weix 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12209-12213
Synthesis of the C?C bonds of ketones relies upon one high‐availability reagent (carboxylic acids) and one low‐availability reagent (organometallic reagents or alkyl iodides). We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N‐hydroxyphthalimide esters and S‐2‐pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl2 to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α‐heteroatoms. The conditions can be employed in the coupling of complex fragments, including a 20‐mer peptide fragment analog of Exendin(9–39) on solid support. 相似文献
18.
Jiang Wang Brian P. Cary Peyton D. Beyer Samuel H. Gellman Daniel J. Weix 《Angewandte Chemie (International ed. in English)》2019,58(35):12081-12085
Synthesis of the C?C bonds of ketones relies upon one high‐availability reagent (carboxylic acids) and one low‐availability reagent (organometallic reagents or alkyl iodides). We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N‐hydroxyphthalimide esters and S‐2‐pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl2 to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α‐heteroatoms. The conditions can be employed in the coupling of complex fragments, including a 20‐mer peptide fragment analog of Exendin(9–39) on solid support. 相似文献
19.
Enrico Marelli Dr. Martin Corpet Sian R. Davies Prof. Dr. Steven P. Nolan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17272-17276
A general catalytic protocol for the α‐arylation of aryl ketones has been developed. It involves the use of a preformed, bench‐stable Pd–N‐heterocyclic carbene pre‐catalyst bearing IHept as an ancillary ligand, and allows the coupling of various functionalized coupling partners at very low catalyst loading. Careful choice of the solvent/base system was crucial to obtain optimum catalyst performance. The pre‐catalyst was also successfully tested in the synthesis of an industrially relevant compound. 相似文献
20.
Gabriele Pupo Dr. Roberta Properzi Prof. Dr. Benjamin List 《Angewandte Chemie (International ed. in English)》2016,55(20):6099-6102
Quaternary stereocenters are found in numerous bioactive molecules. The Tsuji–Trost reaction has proven to be a powerful C?C bond forming process, and, at least in principle, should be well suited to access quaternary stereocenters via the α‐allylation of ketones. However, while indirect approaches are known, the direct, catalytic asymmetric α‐allylation of branched ketones has been elusive until today. By combining “enol catalysis” with the use of CO2 as a formal catalyst for asymmetric catalysis, we have now developed a solution to this problem: we report a direct, highly enantioselective and highly atom‐economic Tsuji–Trost allylation of branched ketones with allylic alcohol. Our reaction delivers products bearing quaternary stereocenters with high enantioselectivity and water as the sole by‐product. We expect our methodology to be of utility in asymmetric catalysis and inspire the design of other highly atom‐economic transformations. 相似文献