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1.
Lewis Acid Mediated Tandem Reaction of Propargylic Alcohols to Tetrazoles Involving CO‐ and CC‐Bond Cleavage Reactions and a CN‐Bond Formation 下载免费PDF全文
Dr. Xian‐Rong Song Ya‐Ping Han Yi‐Feng Qiu Zi‐Hang Qiu Xue‐Yuan Liu Prof. Dr. Peng‐Fei Xu Prof. Dr. Yong‐Min Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12046-12050
A novel and direct synthesis of 1‐aryl‐5‐arylvinyl‐tetrazoles from easily prepared propargylic alcohols and TMSN3 is developed in the presence of TMSCl under mild conditions (TMS=trimethylsilyl). The process involves an allenylazide intermediate, followed by a C?C‐bond cleavage and C?N‐bond formation to afford the desired products. Moreover, this method offers a good functional‐group applicability and can be scaled‐up to grams (yield up to 85 %). 相似文献
2.
Prof. Dr. Li‐Jun Gu Cheng Jin Hong‐Tao Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8741-8744
A novel nickel N‐heterocyclic carbene catalyzed cross‐coupling reaction of aryl aldehydes with boronic esters for the synthesis of aryl ketones was developed. This reaction provides a mild, practical method toward aryl ketones, which are versatile intermediates and building blocks in organic synthesis. 相似文献
3.
The Mechanism of NO Bond Cleavage in Rhodium‐Catalyzed CH Bond Functionalization of Quinoline N‐oxides with Alkynes: A Computational Study 下载免费PDF全文
Yingzi Li Song Liu Zisong Qi Xiaotian Qi Prof. Dr. Xingwei Li Prof. Dr. Yu Lan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10131-10137
Metal‐catalyzed C?H activation not only offers important strategies to construct new bonds, it also allows the merge of important research areas. When quinoline N‐oxide is used as an arene source in C?H activation studies, the N?O bond can act as a directing group as well as an O‐atom donor. The newly reported density functional theory method, M11L, has been used to elucidate the mechanistic details of the coupling between quinoline N?O bond and alkynes, which results in C?H activation and O‐atom transfer. The computational results indicated that the most favorable pathway involves an electrophilic deprotonation, an insertion of an acetylene group into a Rh?C bond, a reductive elimination to form an oxazinoquinolinium‐coordinated RhI intermediate, an oxidative addition to break the N?O bond, and a protonation reaction to regenerate the active catalyst. The regioselectivity of the reaction has also been studied by using prop‐1‐yn‐1‐ylbenzene as a model unsymmetrical substrate. Theoretical calculations suggested that 1‐phenyl‐2‐quinolinylpropanone would be the major product because of better conjugation between the phenyl group and enolate moiety in the corresponding transition state of the regioselectivity‐determining step. These calculated data are consistent with the experimental observations. 相似文献
4.
Copper‐Catalyzed Aerobic Oxidative Inert CC and CN Bond Cleavage: A New Strategy for the Synthesis of Tertiary Amides 下载免费PDF全文
Xiuling Chen Dr. Tieqiao Chen Qiang Li Dr. Yongbo Zhou Prof. Li‐Biao Han Prof. Shuang‐Feng Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12234-12238
A copper‐catalyzed aerobic oxidative amidation reaction of inert C?C bonds with tertiary amines has been developed for the synthesis of tertiary amides, which are significant units in many natural products, pharmaceuticals, and fine chemicals. This method combines C?C bond activation, C?N bond cleavage, and C?H bond oxygenation in a one‐pot protocol, using molecular oxygen as the sole oxidant without any additional ligands. 相似文献
5.
Synthesis of Silaphenalenes by Ruthenium‐Catalyzed Annulation between 1‐Naphthylsilanes and Internal Alkynes through CH Bond Cleavage 下载免费PDF全文
Dr. Yuichiro Tokoro Kengo Sugita Prof. Dr. Shin‐ichi Fukuzawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13229-13232
Ruthenium‐catalyzed annulation of 1‐naphthylsilanes with internal alkynes afforded silaphenalenes through cleavage of the C?H bond at the 8‐position of the naphthalene. [RuH2(CO){P(p‐FC6H4)3}3] efficiently catalyzed the reaction. The use of 1‐naphthyldiphenylsilane as a substrate resulted in a better yield of the annulation product compared to the use of silanes with alkyl groups on the silicon atom. Internal alkynes with both aryl and alkyl groups were tolerated in this reaction. 相似文献
6.
This Focus Review presents recent developments in the cleavage of C? C bonds in organic molecules. Significant progress in C? C activation, including the development of a variety of new synthetic strategies, has contributed to the development of this field over the past few decades. Transition‐metal‐mediated C? C bond cleavage has been shown to be a quite efficient process and several elegant metal‐free methods have also recently been developed. Strained rings have been widely used in C? C cleavage transformations; however, unstrained C? C activation has increasingly caught the attention of organic researchers, which inspired us to clarify the developments in this field. 相似文献
7.
Sabrina Würtemberger‐Pietsch Heidi Schneider Prof. Dr. Todd B. Marder Prof. Dr. Udo Radius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13032-13036
We report the reactions of catecholborane (HBcat; 1 ) with unsaturated and saturated NHCs as well as CAACMe. Mono‐NHC adducts of the type HBcat?NHC (NHC=nPr2Im, iPr2Im, iPr2ImMe, and Dipp2Im) were obtained by stoichiometric reactions of HBcat with the unsaturated NHCs. The reaction of CAACMe with HBcat yielded the B?H activated product CAACMe(H)Bcat via insertion of the carbine‐carbon atom into the B?H bond. The saturated NHC Dipp2SIm reacted in a 2:2 ratio yielding an NHC ring‐expanded product at room temperature forming a six‐membered ?B?C=N?C=C?N? ring via C?N bond cleavage and further migration of the hydrides from two HBcat molecules to the former carbene‐carbon atom. 相似文献
8.
Intramolecular Cooperative CC Bond Cleavage Reaction of 1,3‐Dicarbonyl Compounds with 2‐Iodoanilines to Give o‐(N‐Acylamino)aryl Ketones and Multisubstituted Indoles 下载免费PDF全文
Qi Xing Hui Lv Prof. Dr. Chungu Xia Prof. Dr. Fuwei Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8591-8596
A copper‐catalyzed C?C bond cleavage reaction of 1,3‐dicarbonyl compounds with 2‐iodoanilines was developed. In this process, the ortho effect played an important role in the reactivity and a new reaction pathway that involved a (2‐aminophenyl)‐bis‐(1,3‐dicarbonyl) copper species was clearly observed by a time‐course HRMS analysis of the reaction mixture. Unlike the previous reports, both the nucleophilic and electrophilic parts of the 1,3‐dicarbonyl compound were coupled with 2‐iodoaniline by C?C bond cleavage to form o‐(N‐acylamino)aryl ketones, which could be efficiently converted into multisubstituted indoles. 相似文献
9.
Thorsten vom Stein Dr. Tim den Hartog Dr. Julien Buendia Dr. Spas Stoychev Jakob Mottweiler Prof. Dr. Carsten Bolm Prof. Dr. Jürgen Klankermayer Prof. Dr. Walter Leitner 《Angewandte Chemie (International ed. in English)》2015,54(20):5859-5863
Ruthenium–triphos complexes exhibited unprecedented catalytic activity and selectivity in the redox‐neutral C? C bond cleavage of the β‐O‐4 lignin linkage of 1,3‐dilignol model compounds. A mechanistic pathway involving a dehydrogenation‐initiated retro‐aldol reaction for the C? C bond cleavage was proposed in line with experimental data and DFT calculations. 相似文献
10.
Efficient Synthesis of 1,2,3‐Triazoles by Copper‐Mediated CN and NN Bond Formation Starting From N‐Tosylhydrazones and Amines 下载免费PDF全文
Zhengkai Chen Qiangqiang Yan Hong Yi Zhanxiang Liu Prof. Dr. Aiwen Lei Prof. Dr. Yuhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13692-13697
An effective copper‐mediated synthesis of 1,5‐dialkyl‐4‐aryl‐1,2,3‐triazoles and 1,4‐dialkyl‐5‐aryl‐1,2,3‐triazoles has been achieved by the use of different N‐tosylhydrazones and alkyl amines. The scope of the substrates could be extended from anilines to aliphatic amines when 30 mol % amino acid is added into the reaction mixture. This methodology exhibits many notable features, such as broad substrates scope, high efficiency, and good regioselectivity. Preliminary mechanistic studies indicated that the reaction probably proceeded through a 1‐tosyl‐2‐vinyldiazene intermediate and subsequent aza‐Michael addition and N?N bond formation process. 相似文献
11.
Probing the Limits of Ligand Steric Bulk: Backbone CH Activation in a Saturated N‐Heterocyclic Carbene 下载免费PDF全文
Nicholas Phillips Remi Tirfoin Prof. Simon Aldridge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3825-3830
The consequences of extremely high steric loading have been probed for late transition metal complexes featuring the expanded ring N‐heterocyclic carbene 6‐Dipp. The reluctance of this ligand to form 2:1 complexes with d‐block metals (rationalised on the basis of its percentage buried volume, % Vbur, of 50.8 %) leads to C?H and C?N bond activation processes driven by attack at the backbone β‐CH2 unit. In the presence of IrI (or indeed H+) the net result is the formation of an allyl formamidine fragment, while AuI brings about an additional ring (re‐)closure step via nucleophilic attack at the coordinated alkene. The net transformation of 6‐Dipp in the presence of [(6‐Dipp)Au]+ represents to our knowledge the first example of backbone C?H activation of a saturated N‐heterocyclic carbene, proceeding in this case via a mechanism which involves free carbene in addition to the AuI centre. 相似文献
12.
Rhodium(III)‐Catalyzed Selective ortho‐Olefinations of N‐Acyl and N‐Aroyl Sulfoximines by CH Bond Activation 下载免费PDF全文
Dr. Kanniyappan Parthasarathy Prof. Dr. Carsten Bolm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4896-4900
Two new rhodium‐catalyzed oxidative couplings between sulfoximine derivatives and alkenes by regioselective C?H activation, affording ortho‐olefinated (Heck‐type) products, are reported. A synthetic application of the ortho‐alkenylated products into the corresponding cyclic derivatives has been demonstrated, and a mechanistic rational for the rhodium catalysis is presented. 相似文献
13.
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.
Access to Oxoquinoline Heterocycles by N‐Heterocyclic Carbene Catalyzed Ester Activation for Selective Reaction with an Enone 下载免费PDF全文
Dr. Zhenqian Fu Dr. Ke Jiang Dr. Tingshun Zhu Prof. Dr. Jaume Torres Prof. Dr. Yonggui Robin Chi 《Angewandte Chemie (International ed. in English)》2014,53(25):6506-6510
Organocatalytic ester activation is developed for a highly selective cascade reaction between saturated esters and amino enones. The reaction involves activation of the β‐carbon atom of the ester as a key step. This method allows a single‐step access to multicyclic oxoquinoline‐type heterocycles with high enantiomeric ratios. 相似文献
16.
Density Functional Theory Calculations on Oxidative CC Bond Cleavage and NO Bond Formation of [RuII(bpy)2(diamine)]2+ via Reactive Ruthenium Imide Intermediates 下载免费PDF全文
Dr. Xiangguo Guan Siu‐Man Law Chun‐Wai Tse Dr. Jie‐Sheng Huang Prof. Dr. Chi‐Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15122-15130
DFT calculations are performed on [RuII(bpy)2(tmen)]2+ ( M1 , tmen=2,3‐dimethyl‐2,3‐butanediamine) and [RuII(bpy)2(heda)]2+ ( M2 , heda=2,5‐dimethyl‐2,5‐hexanediamine), and on the oxidation reactions of M1 to give the C?C bond cleavage product [RuII(bpy)2(NH=CMe2)2]2+ ( M3 ) and the N?O bond formation product [RuII(bpy)2(ONCMe2CMe2NO)]2+ ( M4 ). The calculated geometrical parameters and oxidation potentials are in good agreement with the experimental data. As revealed by the DFT calculations, [RuII(bpy)2(tmen)]2+ ( M1 ) can undergo oxidative deprotonation to generate Ru‐bis(imide) [Ru(bpy)2(tmen‐4 H)]+ ( A ) or Ru‐imide/amide [Ru(bpy)2(tmen‐3 H)]2+ ( A′ ) intermediates. Both A and A′ are prone to C?C bond cleavage, with low reaction barriers (ΔG≠) of 6.8 and 2.9 kcal mol?1 for their doublet spin states 2 A and 2 A′ , respectively. The calculated reaction barrier for the nucleophilic attack of water molecules on 2 A′ is relatively high (14.2 kcal mol?1). These calculation results are in agreement with the formation of the RuII‐bis(imine) complex M3 from the electrochemical oxidation of M1 in aqueous solution. The oxidation of M1 with CeIV in aqueous solution to afford the RuII‐dinitrosoalkane complex M4 is proposed to proceed by attack of the cerium oxidant on the ruthenium imide intermediate. The findings of ESI‐MS experiments are consistent with the generation of a ruthenium imide intermediate in the course of the oxidation. 相似文献
17.
Rhodium(III)‐Catalyzed Transannulation of Cyclopropenes with N‐Phenoxyacetamides through CH Activation 下载免费PDF全文
Hang Zhang Kang Wang Bo Wang Heng Yi Fangdong Hu Dr. Changkun Li Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2014,53(48):13234-13238
An efficient rhodium(III)‐catalyzed synthesis of 2H‐chromene from N‐phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three‐carbon unit in rhodium(III)‐catalyzed C(sp2)? H activations. 相似文献
18.
Intramolecular CN Bond Activation and Ring‐Expansion Reactions of N‐Heterocyclic Carbenes 下载免费PDF全文
Dr. Patrick Hemberger Dr. Andras Bodi Johannes H. J. Berthel Prof. Dr. Udo Radius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1434-1438
Intramolecular ring‐expansion reactions (RER) of the N‐heterocyclic carbene 1,3‐dimethylimidazolin‐2‐ylidene were observed upon vacuum ultraviolet (VUV) photoexcitation. Similarly to RERs reported in the solvent phase, for the reaction of NHCs with main‐group‐element hydrides, hydrogen transfer to the NHC carbon atom is the crucial initial step. In an ionization‐mediated protonation, 1,3‐dimethylimidazolin‐2‐ylidene forms an imidazolium ion, which is the rate‐limiting step on the pathway to two six‐membered ring products, namely, methylpyrimidinium and ‐pyrazinium ions. To unravel the reaction path, we have used imaging photoelectron photoion coincidence spectroscopy with VUV synchrotron radiation, as well as high‐level composite method calculations. Similarities and differences between the mechanism in the gas phase and in the condensed phase are discussed. 相似文献
19.
Nickel‐Catalyzed Chemo‐, Regio‐ and Diastereoselective Bond Formation through Proximal CC Cleavage of Benzocyclobutenones 下载免费PDF全文
Dr. Francisco Juliá‐Hernández Dr. Asraa Ziadi Dr. Akira Nishimura Prof. Ruben Martin 《Angewandte Chemie (International ed. in English)》2015,54(33):9537-9541
The first catalytic intermolecular proximal C1? C2 cleavage of benzocyclobutenones (BCB) without prior carbonyl activation or employing noble metals has been developed. This protocol operates at room temperature and is characterized by an exquisite chemo‐, regio‐ and diastereoselectivity profile, constituting a unique platform for preparing an array of elusive carbocyclic skeletons. 相似文献
20.
Hui Wang Julian Koeller Weiping Liu Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15525-15528
C?H/N?O functionalizations by cobalt(III) catalysis allowed the expedient synthesis of a broad range of isoquinolines. Thus, internal and challenging terminal alkynes proved to be viable substrates for an isohypsic annulation, which was shown to proceed by a facile C?H cobaltation. 相似文献