共查询到20条相似文献,搜索用时 15 毫秒
1.
Zengbing Bai Chuangxu Cai Wangjian Sheng Yuxiang Ren Huan Wang 《Angewandte Chemie (International ed. in English)》2020,59(34):14686-14692
Transition‐metal‐catalyzed C?H activation has shown potential in the functionalization of peptides with expanded structural diversity. Herein, the development of late‐stage peptide macrocyclization methods by palladium‐catalyzed site‐selective C(sp2)?H olefination of tryptophan residues at the C2 and C4 positions is reported. This strategy utilizes the peptide backbone as endogenous directing groups and provides access to peptide macrocycles with unique Trp–alkene crosslinks. 相似文献
2.
Errika Voutyritsa Christoforos G. Kokotos 《Angewandte Chemie (International ed. in English)》2020,59(4):1735-1741
Direct alkylation of C(sp2)?H bonds to convert an aldehyde into a ketone is a notorious transformation, due to the laborious challenge of the formation of ketyl or acyl radicals. Herein, we report a green, cheap, metal‐free and efficient method for the hydroacylation of olefins in water. This photochemical protocol utilizes phenylglyoxylic acid, a commercially available small organic molecule, as the photoinitiator, water as the solvent and household fluorescent lamps as the irradiation source, leading to a broad substrate scope of products in moderate to good yields. A wide range of aromatic and aliphatic aldehydes, terminal and non‐terminal alkenes and pharmaceutically relevant molecules can be employed, without the need of directing groups and additives or metal catalysts. 相似文献
3.
Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2020,59(41):17798-17809
In the past decade, multiple catalytic C?H bond functionalization has been successfully applied in natural product synthesis as a strategy to reduce the number of steps, increase overall yield and employ more easily available starting materials. This minireview presents selected examples making use of multiple C?H bond functionalization in conceptually different ways. First, linear syntheses are discussed, wherein multiple C?H functionalization is employed either from simple (hetero)cyclic cores, at a late stage, or to build polycyclic systems. Second, the use of multiple C?H functionalization as a strategic tool in convergent synthesis to access and couple complex fragments is discussed. Information on the scalability of the employed methods is provided when available. The presented cases indicate that multiple C?H functionalization strategies should play a great role to shape the future synthesis of functional complex molecules with improved sustainability. 相似文献
4.
Synthesis of Strained γ‐Lactams by Palladium(0)‐Catalyzed C(sp3)−H Alkenylation and Application to Alkaloid Synthesis 下载免费PDF全文
Dr. Philipp M. Holstein David Dailler Julien Vantourout Janah Shaya Dr. Anthony Millet Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2016,55(8):2805-2809
A variety of strained α‐alkylidene‐γ‐lactams were synthesized by palladium(0)‐catalyzed intramolecular C(sp3)?H alkenylation from easily accessible acyclic and monocyclic bromoalkene precursors. These lactams are valuable intermediates for accessing various classes of mono‐ and bicylic alkaloids containing a pyrrolidine ring, as illustrated with the synthesis of an advanced model of the marine natural product plakoridine A and of the indolizidine alkaloid δ‐coniceine. 相似文献
5.
Xianhai Tian Lina Song A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2020,59(30):12342-12346
While direct nitrene insertions into C?H bonds have become an important tool for building C?N bonds in modern organic chemistry, the generation of nitrene intermediates always requires transition metals, high temperatures, ultraviolet or laser light. We report a mild synthesis of carbazoles and related building blocks through a visible light‐induced intramolecular C?H amination reaction. A striking advantage of this new method is the use of more reactive aryl sulfilimines instead of the corresponding hazardous azides. Different catalysts and divergent light sources were tested. The reaction scope is broad and the product yield is generally high. An efficient gram‐scale synthesis of Clausine C demonstrates the applicability and scalability of this new method. 相似文献
6.
David B. Konrad James A. Frank Prof. Dr. Dirk Trauner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4364-4368
Azobenzenes are versatile photoswitches that can be cycled between their trans‐ and cis‐configuration with light. The wavelengths required for this isomerization are substantially shifted from the UV to the visible range through tetra‐ortho‐chlorination. These halogenated azobenzenes display unique photoswitching characteristics, but their syntheses remain limited and inefficient. A new general method for the synthesis of tetra‐ortho‐chloro azobenzenes has been developed, which relies on direct palladium(II)‐catalyzed C?H activation of pre‐existing standard azobenzenes. This late‐stage functionalization has a broad substrate scope and can be used to create a variety of useful building blocks for the construction of more elaborate redshifted photopharmaceuticals. This method is used to prepare red‐ AzCA‐4 , a photoswitchable vanilloid that enables optical control of the cation channel TRPV1 with visible light. 相似文献
7.
Lin Guo Prof. Dr. Magnus Rueping 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16787-16790
A new and efficient nickel‐catalyzed decarbonylative borylation reaction of carboxylic acid esters with bis(pinacolato)‐diboron has been developed. This transformation allows access to structurally diverse aryl as well as alkenyl and alkyl boronate esters with high reactivity, broad substrate scope, and excellent functional‐group tolerance. Further experiments show that this protocol can be carried out on a gram scale and applied to orthogonal synthetic strategies. 相似文献
8.
Direct Synthesis of Protoberberine Alkaloids by Rh‐Catalyzed C−H Bond Activation as the Key Step 下载免费PDF全文
Dr. Jayachandran Jayakumar Prof. Dr. Chien‐Hong Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1800-1804
A one‐pot reaction of substituted benzaldehydes with alkyne–amines by a Rh‐catalyzed C?H activation and annulation to afford various natural and unnatural protoberberine alkaloids is reported. This reaction provides a convenient route for the generation of a compound library of protoberberine salts, which recently have attracted great attention because of their diverse biological activities. In addition, pyridinium salt derivatives can also be formed in good yields from α,β‐unsaturated aldehydes and amino–alkynes. This reaction proceeds with excellent regioselectivity and good functional group compatibility under mild reaction conditions by using O2 as the oxidant. 相似文献
9.
Mizuho Uryu Taito Hiraga Yoshito Koga Yutaro Saito Kei Murakami Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2020,59(16):6551-6554
Polycyclic aromatic hydrocarbons (PAHs) represent an emerging class of π‐conjugated molecules in the area of optoelectronic devices and materials. Unprecedented synthetic routes to various PAHs from simple phenol derivatives by a palladium‐catalyzed annulative dimerization of phenylene triflate through twofold inter‐ and intramolecular C?H activation have been established. The initially formed partially fused PAHs can be smoothly transformed into a variety of fully fused PAHs by the Scholl reaction. Furthermore, the reactions of phenanthrene‐substituted aryl triflates proceeded regioselectively. The findings inspired the development of a rapid and efficient synthesis of polybenzoacene derivatives. This study not only allows transformation of phenyl triflates, but also discloses a new retrosynthetic strategy towards PAHs, especially polybenzoacenes. 相似文献
10.
Ruthenium(II)‐Catalyzed Synthesis of Spirobenzofuranones by a Decarbonylative Annulation Reaction 下载免费PDF全文
Partha P. Kaishap Gauri Duarah Dr. Bipul Sarma Prof. Dr. Dipak Chetia Dr. Sanjib Gogoi 《Angewandte Chemie (International ed. in English)》2018,57(2):456-460
The first decarbonylative insertion of an alkyne through C?H/C?C activation of six‐membered compounds is reported. The Ru‐catalyzed reaction of 3‐hydroxy‐2‐phenyl‐chromones with alkynes works most efficiently in the presence of the ligand PPh3 to provide spiro‐indenebenzofuranones. Unlike previously reported metal‐catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide. 相似文献
11.
Teresa Ksel Gran Schulz Gerald Drger Andreas Kirschning 《Angewandte Chemie (International ed. in English)》2020,59(30):12376-12380
This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer‐bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2‐functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols. 相似文献
12.
Friedel–Crafts‐Type Intermolecular C−H Silylation of Electron‐Rich Arenes Initiated by Base‐Metal Salts 下载免费PDF全文
Dr. Qin Yin Dr. Hendrik F. T. Klare Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2016,55(9):3204-3207
An electrophilic aromatic substitution (SEAr) with a catalytically generated silicon electrophile is reported. Essentially any commercially available base‐metal salt acts as an initiator/catalyst when activated with NaBArF4 . The thus‐generated Lewis acid then promotes the SEAr of electron‐rich arenes with hydrosilanes but not halosilanes. This new C?H silylation was optimized for FeCl2 /NaBArF4 , affording good yields at catalyst loadings as low as 0.5 mol %. The procedure is exceedingly straightforward and comes close to typical Friedel–Crafts methods, where no added base is needed to absorb the released protons. 相似文献
13.
C−H Activation Enables a Concise Total Synthesis of Quinine and Analogues with Enhanced Antimalarial Activity 下载免费PDF全文
Dr. Daniel H. O' Donovan Dr. Paul Aillard Martin Berger Dr. Aurélien de la Torre Dr. Desislava Petkova Christian Knittl‐Frank Dr. Danny Geerdink Dr. Marcel Kaiser Prof. Dr. Nuno Maulide 《Angewandte Chemie (International ed. in English)》2018,57(33):10737-10741
We report a novel approach to the classical natural product quinine that is based on two stereoselective key steps, namely a C?H activation and an aldol reaction, to unite the two heterocyclic moieties of the target molecule. This straightforward and flexible strategy enables a concise synthesis of natural (?)‐quinine, the first synthesis of unnatural (+)‐quinine, and also provides access to unprecedented C3‐aryl analogues, which were prepared in only six steps. We additionally demonstrate that these structural analogues exhibit improved antimalarial activity compared with (?)‐quinine both in vitro and in mice infected with Plasmodium berghei. 相似文献
14.
Riki Das Dr. Manmohan Kapur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16986-16990
A new class of Weinreb amides has been developed as directing groups for the ruthenium‐catalysed regioselective oxidative C?H olefination. The new Weinreb amides successfully inhibit the N?O bond reductive cleavage usually associated with the cationic ruthenium system, thereby keeping intact the synthetic utility of Weinreb amides. Mechanistic studies reveal interesting aspects of the directing group capabilities of Weinreb amides when compared to simple amides of similar structures. 相似文献
15.
M. Sc. Markus Warnke Tobias Jung Dr. Juri Dermer Karin Hipp Dr. Nico Jehmlich Prof. Dr. Martin von Bergen Sascha Ferlaino Dr. Alexander Fries Prof. Dr. Michael Müller Prof. Dr. Matthias Boll 《Angewandte Chemie (International ed. in English)》2016,55(5):1881-1884
The hydroxylation of vitamin D3 (VD3, cholecalciferol) side chains to give 25‐hydroxyvitamin D3 (25OHVD3) is a crucial reaction in the formation of the circulating and biologically active forms of VD3. It is usually catalyzed by cytochrome P450 monooxygenases that depend on complex electron donor systems. Cell‐free extracts and a purified Mo enzyme from a bacterium anaerobically grown with cholesterol were employed for the regioselective, ferricyanide‐dependent hydroxylation of VD3 and proVD3 (7‐dehydrocholesterol) into the corresponding tertiary alcohols with greater than 99 % yield. Hydroxylation of VD3 strictly depends on a cyclodextrin‐assisted isomerization of VD3 into preVD3, the actual enzymatic substrate. This facile and robust method developed for 25OHVD3 synthesis is a novel example for the concept of substrate‐engineered catalysis and offers an attractive alternative to chemical or O2 /electron‐donor‐dependent enzymatic procedures. 相似文献
16.
Takeru Torigoe Dr. Toshimichi Ohmura Prof. Michinori Suginome 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10415-10419
Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C?H bond of a methoxy group in 1‐methoxy‐2‐(arylethynyl)benzenes across a carbon–carbon triple bond took place efficiently either in toluene at 110 °C or in p‐xylene at 135 °C in the presence of an iridium catalyst. The initial 5‐exo cyclization products underwent double‐bond migration during the reaction to give 3‐(arylmethyl)benzofurans in high yields. 相似文献
17.
Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent‐ and Metal‐Free Anodic Cross‐Coupling Reaction 下载免费PDF全文
Anton Wiebe Dr. Dieter Schollmeyer Dr. Katrin M. Dyballa Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2016,55(39):11801-11805
The oxidative cross‐coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2′‐biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent‐free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale‐up and inherently safe. The implementation of O‐silyl‐protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2′‐biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl‐protected 2,2′‐biphenols are versatile building blocks that usually require tedious or low‐yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross‐coupling reactions. 相似文献
18.
Yan Lin Wei‐Yang Ma Zheng Xu Zhan‐Jiang Zheng Jian Cao Ke‐Fang Yang Yu‐Ming Cui Li‐Wen Xu 《化学:亚洲杂志》2019,14(12):2082-2085
A palladium‐catalyzed chelation‐assisted enantioselective C?H olefination of symmetrically diaryl‐substituted tetraorganosilicon derivatives was developed, enabling the generation of nitrogen‐containing silicon‐stereogenic tetraorganosilicon compounds with modest to good yields and good to excellent enantioselectivities (up to 95.5:4.5 e.r.). The Thorpe–Ingold effect exerted by the substituents on silicon was observed to have a profound influence on formation of olefinated products which were further converted into other relevant chiral organosilanes without the loss of enantiomeric purity, thus demonstrating the synthetic utility of the developed enantioselective olefination. 相似文献
19.
Daniel Zell Qingqing Bu Dr. Milica Feldt Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2016,55(26):7408-7412
Cationic cobalt complexes enable unprecedented cobalt‐catalyzed C?H/C?C functionalizations with unique selectivity features. The versatile cobalt catalyst proved broadly applicable, enabled efficient C?H/C?C cleavage at room temperature, and delivered Z‐alkenes with excellent diastereocontrol. 相似文献
20.
Dr. Naoki Ishida Yusuke Masuda Sho Uemoto Prof. Dr. Masahiro Murakami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6524-6527
A photo‐induced carboxylation reaction of allylic C?H bonds of simple alkenes with CO2 is prompted by means of a ketone and a copper complex. The unique carboxylation reaction proceeds through a sequence of an endergonic photoreaction of ketones with alkenes forming homoallyl alcohol intermediates and a thermal copper‐catalyzed allyl transfer reaction from the homoallyl alcohols to CO2 through C?C bond cleavage. 相似文献