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Rhodium(II)‐Catalyzed Intramolecular Cycloisomerizations of Methylenecyclopropanes with N‐Sulfonyl 1,2,3‐Triazoles 下载免费PDF全文
Kai Chen Zi‐Zhong Zhu Yong‐Sheng Zhang Dr. Xiang‐Ying Tang Prof. Min Shi 《Angewandte Chemie (International ed. in English)》2014,53(26):6645-6649
A novel rhodium(II)‐catalyzed tandem cycloisomerization of methylenecyclopropanes (MCPs) with N‐sulfonyl 1,2,3‐triazoles is disclosed. The reaction produces a series of highly functionalized polycyclic N heterocycles via a rhodium imino carbene intermediate. A distinct feature of this divergent synthesis is that different types of substrates control the reaction pathways. Moreover, several interesting transformations of these products to construct diazabicyclo[3.2.1]octane derivatives are also reported. 相似文献
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Iron(III)‐Catalyzed Cycloisomerizations of Acetal–Vinylidenecyclopropanes: An Efficient Synthetic Route to 1,2‐Disubstituted Cyclobutenes 下载免费PDF全文
Song Yang Wei Yuan Dr. Qin Xu Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15964-15969
A novel iron(III)‐catalyzed intramolecular cycloisomerization of acetal–vinylidenecyclopropanes to afford a series of halogenated 1,2‐disubstituted cyclobutenes tethered with a tetrahydropyrrole has been developed. The reaction is thought to proceed through a formal iron‐catalyzed Prins cyclization followed by a ring‐enlarging rearrangement of the methylenecyclopropane carbocation. The present protocol provides an alternative route to functionalized disubstituted cyclobutenes and the corresponding products could be successfully transformed into eight‐membered oxacyclic products. 相似文献
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Dr. Marie Betou Dr. Louise Male Prof. Jonathan W. Steed Dr. Richard S. Grainger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6505-6517
In an approach to the biologically important 6‐azabicyclo[3.2.1]octane ring system, the scope of the tandem 4‐exo‐trig carbamoyl radical cyclization—dithiocarbamate group transfer reaction to ring‐fused β‐lactams is evaluated. β‐Lactams fused to five‐, six‐, and seven‐membered rings are prepared in good to excellent yield, and with moderate to complete control at the newly formed dithiocarbamate stereocentre. No cyclization is observed with an additional methyl substituent on the terminus of the double bond. Elimination of the dithiocarbamate group gives α,β‐ or β,γ‐unsaturated lactams depending on both the methodology employed (base‐mediated or thermal) and the nature of the carbocycle fused to the β‐lactam. Fused β‐lactam diols, obtained from catalytic OsO4‐mediated dihydroxylation of α,β‐unsaturated β‐lactams, undergo semipinacol rearrangement via the corresponding cyclic sulfite or phosphorane to give keto‐bridged bicyclic amides by exclusive N‐acyl group migration. A monocyclic β‐lactam diol undergoes Appel reaction at a primary alcohol in preference to semipinacol rearrangement. Preliminary investigations into the chemo‐ and stereoselective manipulation of the two carbonyl groups present in a representative 7,8‐dioxo‐6‐azabicyclo[3.2.1]octane rearrangement product are also reported. 相似文献
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Intermolecular σ‐Bond Cross‐Exchange Reaction between Cyclopropenones and (Benzo)silacyclobutanes: Straightforward Access towards Sila(benzo)cycloheptenones 下载免费PDF全文
Wen‐Tao Zhao Fang Gao Prof. Dr. Dongbing Zhao 《Angewandte Chemie (International ed. in English)》2018,57(21):6329-6332
Described herein is the first intermolecular σ‐bond exchange reaction between the C?C bond of cyclopropenones and C?Si bond of (benzo)silacyclobutanes and it proceeds smoothly by treatment with either 1 mol % of a palladium or 2 mol % of a nickel catalyst. This reaction constitutes an unprecedented route for the synthesis of various sila(benzo)suberones. And it is also the first example of a σ‐bond exchange reaction involving cyclopropenones. 相似文献
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Jun‐Jie Shen Prof. Shou‐Fei Zhu Dr. Yan Cai Huan Xu Xiu‐Lan Xie Prof. Qi‐Lin Zhou 《Angewandte Chemie (International ed. in English)》2014,53(48):13188-13191
An iron‐catalyzed asymmetric intramolecular cyclopropanation was realized in high yields and excellent enantioselectivity (up to 97 % ee) by using the iron complexes of chiral spiro‐bisoxazoline ligands as catalysts. The superiority of iron catalysts exhibited in this reaction demonstrated the potential abilities of this sustainable metal in asymmetric carbenoid transformation reactions. 相似文献
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Cyclobutene Formation in PtCl2‐Catalyzed Cycloisomerizations of Heteroatom‐Tethered 1,6‐Enynes 下载免费PDF全文
Zhenjie Ni Dr. Laurent Giordano Dr. Alphonse Tenaglia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11703-11706
Aza(oxa)bicyclo[3.2.0]heptenes are accessed through the PtCl2‐catalyzed cycloisomerizations of heteroatom‐tethered 1,6‐enynes featuring a terminal alkyne and amide as the solvent. It is shown that the weak coordinating properties of the solvent and alkyl substituent(s) at the propargylic carbon atom favor the formation of cyclobutenes instead of other possible cycloisomerization products such as 1,3‐diene derivatives or cyclopropane‐fused heterocycles. 相似文献
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The “click chemistry” of using organic azides and terminal alkynes is arguably the most efficient and straightforward route to the synthesis of 1,2,3‐triazoles. In this paper, an alternative and direct access to ethyl 1‐(4‐methoxyphenyl)‐5‐phenyl‐1H‐1,2,3‐triazole‐4‐carboxylate is described. Treatment of ethyl diazoacetate with 4‐methoxyaniline derived aryl imines in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene provided fully substituted 1,2,3‐triazoles in good to high chemical yields. The base‐mediated reaction tolerates various substituted phenyl imines as well as ethyl diazoacetate or the more bulky diazoacetamide. A reasonable mechanism is proposed that involves the addition of an imine nitrogen atom to the terminal nitrogen atom of the diazo compound, followed by aromatization to give the 1,2,3‐triazole. The presence of the 4‐carboxy group is advantageous as it can be easily transformed into other functional groups. 相似文献
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Dirhodium(II)‐Catalyzed Annulation of Enoldiazoacetamides with α‐Diazoketones: An Efficient and Highly Selective Approach to Fused and Bridged Ring Systems 下载免费PDF全文
Dr. Qing‐Qing Cheng Julietta Yedoyan Dr. Hadi Arman Prof. Dr. Michael P. Doyle 《Angewandte Chemie (International ed. in English)》2016,55(18):5573-5576
A dirhodium(II)‐catalyzed annulation reaction between two structurally different diazocarbonyl compounds furnishes the donor–acceptor cyclopropane‐fused benzoxa[3.2.1]octane scaffold with excellent chemo‐, regio‐, and diastereoselectivity under exceptionally mild conditions. The composite transformation occurs by [3+2]‐cycloaddition between donor–acceptor cyclopropenes generated from enoldiazoacetamides and carbonyl ylides formed from intramolecular carbene–carbonyl cyclization in one pot with one catalyst. The annulation products can be readily transformed into benzoxa[3.3.1]nonane and hexahydronaphthofuran derivatives with exact stereocontrol. This method allows the efficient construction of three fused and bridged ring systems, all of which are important skeletons of numerous biologically active natural products. 相似文献
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Sheng Feng Prof. Fanyang Mo Dr. Ying Xia Zhenxing Liu Zhen Liu Prof. Yan Zhang Prof. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2016,55(49):15401-15405
The rhodium(I)‐catalyzed C?C bond activation reaction of siloxyvinylcyclopropanes with diazoesters demonstrates a novel mode of C?C bond cleavage of siloxyvinvylcyclopanes. The alkene products were obtained as single E‐configured isomers in good yields. A σ,η3‐allyl rhodium complex, which has been previously proposed as the key intermediate in rhodium(I)‐catalyzed cycloaddition of vinylcyclopropanes, has been isolated and characterized by X‐ray crystallography. 相似文献
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Micol Santi Darren M. C. Ould Jan Wenz Yashar Soltani Rebecca L. Melen Thomas Wirth 《Angewandte Chemie (International ed. in English)》2019,58(23):7861-7865
A novel metal‐free synthesis of 3,3‐disubstituted benzofuran‐2‐(3H)‐ones through reacting α‐aryl‐α‐diazoacetates with triarylboranes is presented. Initially, triarylboranes were successfully investigated in α‐arylations of α‐diazoacetates, however in the presence of a heteroatom in the ortho position, the boron enolate intermediate undergoes an intramolecular rearrangement to form a quaternary center. The intermediate cyclizes to afford valuable 3,3‐disubstituted benzofuranones in good yields. 相似文献
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Trinadh Kaicharla Tony Roy Manikandan Thangaraj Dr. Rajesh G. Gonnade Dr. Akkattu T. Biju 《Angewandte Chemie (International ed. in English)》2016,55(34):10061-10064
Lewis acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with 2‐naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene‐fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel–Crafts‐type addition of 2‐naphthols to cyclopropanes takes place, thus affording functionalized 2‐naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields. 相似文献
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Synthesis of α‐Aryl Esters and Nitriles: Deaminative Coupling of α‐Aminoesters and α‐Aminoacetonitriles with Arylboronic Acids 下载免费PDF全文
Guojiao Wu Yifan Deng Chaoqiang Wu Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2014,53(39):10510-10514
Transition‐metal‐free synthesis of α‐aryl esters and nitriles using arylboronic acids with α‐aminoesters and α‐aminoacetonitriles, respectively, as the starting materials has been developed. The reaction represents a rare case of converting C(sp3)? N bonds into C(sp3)? C(sp2) bonds. The reaction conditions are mild, demonstrate good functional‐group tolerance, and can be scaled up. 相似文献