共查询到20条相似文献,搜索用时 15 毫秒
1.
Dr. Amanda Sølvhøj Andreas Ahlburg Prof. Dr. Robert Madsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16272-16279
A new coupling reaction has been developed in which β‐bromostyrenes react with ethers and tertiary amines to introduce the styryl group in the α‐position. The transformation is mediated by Me2Zn/O2 with 10 % MnCl2 and is believed to proceed by a radical addition–elimination mechanism. The ether and the amine are employed as solvent and the coupling takes place through the most stable α radical for unsymmetrical substrates. The products are obtained in moderate to good yields as the pure E isomers. The coupling can be achieved with a range of smaller cyclic and acyclic ethers/amines as well as various substituted β‐bromostyrenes. 相似文献
2.
Ruthenium‐Catalyzed Oxidative Coupling of Primary Amines with Internal Alkynes through CH Bond Activation: Scope and Mechanistic Studies 下载免费PDF全文
Sara Ruiz Dr. Pedro Villuendas Dr. Manuel A. Ortuño Prof. Dr. Agustí Lledós Dr. Esteban P. Urriolabeitia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8626-8636
The oxidative coupling of primary amines with internal alkynes catalyzed by Ru complexes is presented as a general atom‐economy methodology with a broad scope of applications in the synthesis of N‐heterocycles. Reactions proceed through regioselective C?H bond activation in 15 minutes under microwave irradiation or in 24 hours with conventional heating. The synthesis of 2,3,5‐substituted pyridines, benzo[h]isoquinolines, benzo[g]isoquinolines, 8,9‐dihydro‐benzo[de]quinoline, 5,6,7,8‐tetrahydroisoquinolines, pyrido[3,4g]isoquinolines, and pyrido[4,3g]isoquinolines is achievable depending on the starting primary amine used. DFT calculations on a benzylamine substrate support a reaction mechanism that consists of acetate‐assisted C?H bond activation, migratory‐insertion, and C?N bond formation steps that involve 28–30 kcal mol?1. The computational study is extended to additional substrates, namely, 1‐naphthylmethyl‐, 2‐methylallyl‐, and 2‐thiophenemethylamines. 相似文献
3.
A Bioinspired Catalytic Aerobic Oxidative CH Functionalization of Primary Aliphatic Amines: Synthesis of 1,2‐Disubstituted Benzimidazoles 下载免费PDF全文
Khac Minh Huy Nguyen Dr. Martine Largeron 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12606-12610
Aerobic oxidative C?H functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2‐disubstituted benzimidazoles that play an important role as drug discovery targets. This one‐pot atom‐economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non‐activated aliphatic amines that remain challenging substrates for non‐enzymatic catalytic aerobic systems. 相似文献
4.
Ligand‐Enabled Catalytic CH Arylation of Aliphatic Amines by a Four‐Membered‐Ring Cyclopalladation Pathway 下载免费PDF全文
Dr. Chuan He Prof. Matthew J. Gaunt 《Angewandte Chemie (International ed. in English)》2015,54(52):15840-15844
A palladium‐catalyzed C? H arylation of aliphatic amines with arylboronic esters is described, proceeding through a four‐membered‐ring cyclopalladation pathway. Crucial to the successful outcome of this reaction is the action of an amino‐acid‐derived ligand. A range of hindered secondary amines and arylboronic esters are compatible with this process and the products of the arylation can be advanced to complex polycyclic molecules by sequential C? H activation reactions. 相似文献
5.
Palladium‐Catalyzed Construction of Heteroatom‐Containing π‐Conjugated Systems by Intramolecular Oxidative CH/CH Coupling Reaction 下载免费PDF全文
Kenta Saito Dr. Prasanna Kumara Chikkade Prof. Dr. Motomu Kanai Prof. Dr. Yoichiro Kuninobu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8365-8368
Synthesis of heteroatom‐containing ladder‐type π‐conjugated molecules was successfully achieved via a palladium‐catalyzed intramolecular oxidative C?H/C?H cross‐coupling reaction. This reaction provides a variety of π‐conjugated molecules bearing heteroatoms, such as nitrogen, oxygen, phosphorus, and sulfur atoms, and a carbonyl group. The π‐conjugated molecules were synthesized efficiently, even in gram scale, and larger π‐conjugated molecules were also obtained by a double C?H/C?H cross‐coupling reaction and successive oxidative cycloaromatization. 相似文献
6.
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
7.
M. Sc. Jie Li Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2015,54(12):3635-3638
Carboxylate assistance proved to be the key for the success of efficient cobalt(III)‐catalyzed C? H cyanations. Thus, an in situ generated cationic cobalt complex was identified as a versatile catalyst for the site‐selective synthesis of various aromatic and heteroaromatic nitriles with ample substrate scope. 相似文献
8.
Classical‐Reaction‐Driven Stereo‐ and Regioselective C(sp3)–H Functionalization of Aliphatic Amines 下载免费PDF全文
A large variety of synthetic methods have been developed for the synthesis of functionalized aliphatic amines because of their broad spectrum of application. Metallic reagents/catalysts and/or toxic oxidants are involved in most of the cases. Direct C? H functionalization of aliphatic amines via their classical condensation reactions with suitable carbonyl compounds is advantageous because this method avoids hazardous metallic reagents, toxic oxidants and pre‐activation/pre‐functionalization step(s). In this account, the concept of direct C? H functionalization of aliphatic amines based on the classical condensation–isomerization–addition (CIA) strategy followed by recent contributions from our ongoing research in the field along with relevant examples from other groups are described. Successes in stereo‐ and regioselective C? C and C? O bond formation via direct α‐ as well as β‐C(sp3)–H functionalization are discussed.
9.
Yang Yang Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (International ed. in English)》2014,53(33):8677-8681
A copper‐based catalytic technique for the regioselective ortho C? H cyanation of vinylarenes has been developed. This method provides an effective means for the selective functionalization of vinylarene derivatives. A copper‐catalyzed cyanative dearomatization mechanism is proposed to account for the regiochemical course of this reaction. 相似文献
10.
Mechanistic Study on Rh‐Catalyzed Stereoselective CC/CH Activation of tert‐Cyclobutanols 下载免费PDF全文
Dr. Haizhu Yu Dr. Chen Wang Yimeng Yang Prof. Zhi‐Min Dang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3839-3848
A mechanistic study was performed on the Rh‐catalyzed stereoselective C?C/C?H activation of tert‐cyclobutanols. The present study corroborated the previous proposal that the reaction occurs by metalation, β‐C elimination, 1,4‐Rh transfer, C?O insertion, and a final catalyst‐regeneration step. The rate‐determining step was found to be the 1,4‐Rh transfer step, whereas the stereoselectivity‐determining step did not correspond to any of the aforementioned steps. It was found that both the thermodynamic stability of the product of the β‐C elimination and the kinetic feasibility of the 1,4‐Rh transfer and C?O insertion steps made important contributions. In other words, three steps (i.e., β‐C elimination, 1,4‐Rh transfer, and C?O insertion) were found to be important in determining the configurations of the two quaternary stereocenters. 相似文献
11.
A Highly Efficient Gold‐Catalyzed Photoredox α‐C(sp3)H Alkynylation of Tertiary Aliphatic Amines with Sunlight 下载免费PDF全文
Dr. Jin Xie Dr. Shuai Shi M. Sc. Tuo Zhang M. Sc. Nina Mehrkens Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2015,54(20):6046-6050
A new α‐C(sp3)? H alkynylation of unactivated tertiary aliphatic amines with 1‐iodoalkynes as radical alkynylating reagents in the presence of [Au2(μ‐dppm)2]2+ in sunlight provides propargylic amines. Based on mechanistic studies, a C? C coupling of an α‐aminoalkyl radical and an alkynyl radical is proposed for the C(sp3)? C(sp) bond formation. The mild, convenient, efficient, and highly selective C(sp3)? H alkynylation reaction shows excellent regioselectivity and good functional‐group compatibility. A scale‐up to gram quantities is possible with sunlight used as a clean and sustainable energy source. 相似文献
12.
Dehydrogenative Carbon–Carbon Bond Formation Using Alkynyloxy Moieties as Hydrogen‐Accepting Directing Groups 下载免费PDF全文
Dr. Yasunori Minami Tatsuro Kodama Prof. Dr. Tamejiro Hiyama 《Angewandte Chemie (International ed. in English)》2015,54(40):11813-11816
In the presence of a catalyst system consisting of Pd(OAc)2, PCy3, and Zn(OAc)2, the reaction of alkynyl aryl ethers with bicycloalkenes, α,ß‐unsaturated esters, or heteroarenes results in the site‐selective cleavage of two C? H bonds followed by the formation of C? C bonds. In all cases, the alkynyloxy group acts as a directing group for the activation of an ortho C? H bond and as a hydrogen acceptor, thus rendering the use of additives such as an oxidant or base unnecessary. 相似文献
13.
Divergent Reactivity in Palladium‐Catalyzed Annulation with Diarylamines and α,β‐Unsaturated Acids: Direct Access to Substituted 2‐Quinolinones and Indoles 下载免费PDF全文
Dr. Rajesh Kancherla Togati Naveen Prof. Debabrata Maiti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8723-8726
A palladium‐catalyzed C?H activation strategy has been successfully employed for exclusive synthesis of a variety of 3‐substituted indoles. A [3+3] annulation for synthesizing substituted 2‐quinolinones was recently developed by reaction of α,β‐unsaturated carboxylic acids with diarylamines under acidic conditions. In the present work, an analogous [3+2] annulation is achieved from the same set of starting materials under basic conditions to generate 1,3‐disubstituted indoles exclusively. Mechanistic studies revealed an ortho‐palladation–π‐coordination–β‐migratory insertion–β‐hydride elimination reaction sequence to be operative under the reaction conditions. 相似文献
14.
Dr. Rishikesh Narayan Dr. Kiran Matcha Dr. Andrey P. Antonchick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14678-14693
The formation of C?C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C?C bond‐forming reactions are well‐known challenges. To achieve this goal through direct functionalization of C?H bonds in both of the coupling partners represents the state‐of‐the‐art in organic synthesis. Oxidative C?C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C?C bond‐forming reactions through direct C?H bond functionalization under completely metal‐free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms. 相似文献
15.
Ruthenium(II)‐Catalyzed Oxidative CH Alkenylations of Sulfonic Acids,Sulfonyl Chlorides and Sulfonamides 下载免费PDF全文
Wenbo Ma Ruhuai Mei Giammarco Tenti Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15248-15251
Twofold C?H functionalization of aromatic sulfonic acids was achieved with an in situ generated ruthenium(II) catalyst. The optimized cross‐dehydrogenative alkenylation protocol proved applicable to differently substituted arenes and a variety of alkenes, including vinyl arenes, sulfones, nitriles and ketones. The robustness of the ruthenium(II) catalyst was demonstrated by the chemoselective oxidative olefination of sulfonamides as well as sulfonyl chlorides. Mechanistic studies provided support for a reversible, acetate‐assisted C?H ruthenation, along with a subsequent olefin insertion. 相似文献
16.
Regio‐ and Diastereoselective and Enantiospecific Metal‐Free C(sp3)H Arylation: Facile Access to Optically Active 5‐Aryl 2,5‐Disubstituted Pyrrolidines 下载免费PDF全文
Surajit Haldar Subhra Kanti Roy Bholanath Maity Prof. Dr. Debasis Koley Prof. Dr. Chandan K. Jana 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15290-15298
Optically active 5‐aryl 2,5‐disubstituted pyrrolidines are the principal structural moiety of many bioactive compounds including natural products and catalysts for asymmetric synthesis. A highly regio‐ and diastereoselective and enantiospecific method for direct C?H arylation of aliphatic amine has been developed. Structurally diverse enantiopure arylated pyrrolidines were synthesized from commercially available starting materials, through a single‐step three‐component reaction under metal‐ and oxidant‐free conditions. Furthermore, the complex analogous structure of CCK antagonist RP 66803 and angiotensin‐converting enzyme inhibitors was easily constructed using the synthesized arylated pyrrolidine derivative. Detailed theoretical calculations (M06‐2X/TZVPP/SMD//M06‐2X/6‐31+G(d,p) level) were also carried to investigate the mechanism and high level of stereocontrol involved in this direct sp3 C?H arylation reaction. Preference for a given regio‐ and stereoselectivity in the arylated product can be explained through elucidation of the mechanism for dehydration, generating azomethine ylide, and for the final re‐aromatization step. The calculated energies reveals that the re‐aromatization step is essentially rate determining, accompanying an activation barrier of Δ≠${G{{{\rm S}\hfill \atop {\rm L}\hfill}}}$ =25.6 kcal mol?1. 相似文献
17.
Synthesis of Spirocyclic Enones by Rhodium‐Catalyzed Dearomatizing Oxidative Annulation of 2‐Alkenylphenols with Alkynes and Enynes 下载免费PDF全文
Szymon Kujawa Dr. Daniel Best Dr. David J. Burns Prof. Hon Wai Lam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8599-8602
The dearomatizing oxidative annulation of 2‐alkenylphenols with alkynes and enynes proceeds with high yields and regioselectivities under RhIII catalysis. These reactions are successful using Cu(OAc)2 or air as the stoichiometric oxidant, and provide spirocyclic enones, the basic ring system of which appears in several natural products. Application of this process to the preparation of a highly functionalized tetracycle is also demonstrated. 相似文献
18.
Shuo Guo Xiaofei Zhang Prof. Dr. Pingping Tang 《Angewandte Chemie (International ed. in English)》2015,54(13):4065-4069
The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic C? H bonds employs a silver‐based reagent. The reaction is operationally simple, scalable, and proceeds under aqueous conditions in air. Furthermore, its broad scope and good functional‐group compatibility were demonstrated by applying this method to the selective trifluoromethylthiolation of natural products and natural‐product derivatives. 相似文献
19.
Dr. Brian N. Laforteza Kelvin S. L. Chan Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2015,54(38):11143-11146
The commonly used para‐nitrobenzenesulfonyl (nosyl) protecting group is employed to direct the C? H activation of amines for the first time. An enantioselective ortho‐C? H cross‐coupling between nosyl‐protected diarylmethylamines and arylboronic acid pinacol esters has been achieved utilizing chiral mono‐N‐protected amino acid (MPAA) ligands as a promoter. 相似文献
20.
Rhodium‐Catalyzed Annulative Coupling of 3‐Phenylthiophenes with Alkynes Involving Double C‐H Bond Cleavages 下载免费PDF全文
Tomonori Iitsuka Dr. Koji Hirano Prof. Dr. Tetsuya Satoh Prof. Dr. Masahiro Miura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):385-389
Double C?H bond activation took place efficiently upon treatment of 3‐phenylthiophenes with alkynes in the presence of a rhodium catalyst and a copper salt oxidant to form the corresponding naphthothiophene derivatives. Dehydrogenative coupling with alkenes was also found to occur on the phenyl moiety rather than the thiophene ring. These reactions provide straightforward synthetic methods for π‐conjugated molecules involving a thiophene unit from readily available, simple building blocks. 相似文献