共查询到20条相似文献,搜索用时 250 毫秒
1.
Dr. Xiaoyu Han Dr. Weijun Yao Dr. Tianli Wang Ziyu Yan Jacek Kwiatkowski Prof. Dr. Yixin Lu 《Angewandte Chemie (International ed. in English)》2014,53(22):5643-5647
An enantioselective synthesis of spiropyrazolones from allenoate‐derived MBH acetates and pyrazolones through a phosphine‐mediated [4+1] annulation process has been developed. Spiropyrazolones were readily prepared in good chemical yields and good to high enantioselectivities. This is the first asymmetric example in which α‐substituted allenoates were utilized as a C4 synthon for phosphine‐catalyzed [4+1] annulation. 相似文献
2.
[1+1+3] Annulation of Diazoenals and Vinyl Azides: Direct Synthesis of Functionalized 1‐Pyrrolines through Olefination 下载免费PDF全文
Vinaykumar Kanchupalli Dr. Sreenivas Katukojvala 《Angewandte Chemie (International ed. in English)》2018,57(19):5433-5437
A dirhodium carboxylate catalyzed [1+1+3] annulation reaction of diazoenals and vinyl azides that gives synthetically important enal‐functionalized 1‐pyrroline derivatives was developed. The reaction involves a novel rhodium‐catalyzed olefination of diazoenals with vinyl azides via electrophilic enal carbenoids, resulting in a new class of enal acrylates. The annulation reaction was used for the direct synthesis of valuable deuterated 1‐pyrrolines. Structural diversification of the enal‐functionalized 1‐pyrrolines resulted in the biologically important pyrrolidine‐fused oxaziridine, amino acid derivatives, and a 6‐azabicyclo[3.2.1]octane motif present in polycyclic alkaloids. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(16):4611-4615
Rhodium‐catalyzed C(sp2)−H functionalization reactions of 4‐aryl‐5‐pyrazolones followed by [3+2] annulation reactions with alkynes provide rapid access to highly enantioenriched five‐membered‐ring 4‐spiro‐5‐pyrazolones. The use of a chiral SCpRh catalyst enabled the synthesis of a large range of spiropyrazolones with all‐carbon quaternary stereogenic centers in up to 99 % yield and 98 % ee from readily available substrates. 相似文献
4.
Skeletal Rearrangement in the ZnII‐Catalyzed [4+2]‐Annulation of Disubstituted N‐Hydroxy Allenylamines with Nitrosoarenes to Yield Substituted 1,2‐Oxazinan‐3‐one Derivatives 下载免费PDF全文
Pankaj Sharma Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15881-15887
This work reports zinc‐catalyzed [4+2]‐annulation reactions of disubstituted N‐hydroxy allenylamines with nitrosoarenes to afford substituted 1,2‐oxazinan‐3‐ones with a skeletal rearrangement. This annulation is applicable to a reasonable scope of allenylamines and nitrosoarenes. Our control experiments indicate that nitrosobenzene can also implement this annulation through a radical annulation path, but with poor efficiency. Zn(OTf)2 or AgOTf greatly improves the efficiency of this [4+2]‐annulation; the effect of these metal species is discussed in detail. 相似文献
5.
Chuan‐Chuan Wang Zhi‐Wei Ma Ya‐Li Qu Zhi‐Jing Liu Xiao‐Pei Chen Jing Zhou Ya‐Jing Chen 《化学:亚洲杂志》2020,15(5):560-563
An efficient preparation of sulfamate‐fused 2‐aminopyrroles was achieved through an isocyanide‐based three‐component [1+2+2] annulation of isocyanides, dialkyl acetylenedicarboxylates, and sulfamate‐derived cyclic imines in good to excellent yields (up to 99 %). This reaction proceeds smoothly without any activation or modification of substances under neutral and metal‐free conditions. The reaction could also be conveniently performed on a gram scale. 相似文献
6.
Rhodium(III)‐Catalyzed [3+2]/[5+2] Annulation of 4‐Aryl 1,2,3‐Triazoles with Internal Alkynes through Dual C(sp2)H Functionalization 下载免费PDF全文
Yuan Yang Ming‐Bo Zhou Xuan‐Hui Ouyang Rui Pi Dr. Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2015,54(22):6595-6599
A rhodium(III)‐catalyzed [3+2]/[5+2] annulation of 4‐aryl 1‐tosyl‐1,2,3‐triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7‐cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp2)? H functionalization, and [3+2]/[5+2] annulation. 相似文献
7.
Formal [2+2+1] cycloaddition reaction involving acetylenes, aromatic imines, and CO was achieved by radical chain reaction, which gave five‐membered unsaturated lactams in modest to good yields. When we used 5‐chloropentyne, sequential carbonylation took place accompanied with double annulation events to give a cyclohexanone‐fused lactam in excellent stereoselectivity. 相似文献
8.
Jiaqing Xu Wenjun Yang Wangyu Shi Biming Mao Yan Lin Yumei Xiao Hongchao Guo 《Tetrahedron》2019,75(26):3609-3616
A DMAP-catalyzed [4 + 2] annulation of α-substituted allenoates with unsaturated pyrazolones has been achieved in dichloromethane at 40 °C, providing multisubstituted tetrahydropyrano [2,3-c]pyrazoles in good to excellent yields with moderate to good Z/E ratios. The allenoates worked as two-carbon synthons in the reaction. 相似文献
9.
The base‐controlled mechanisms for N‐heterocyclic carbene (NHC)‐catalyzed divergent [3+3] and [3+2] annulation reactions were examined by using the DFT method. The reaction initiates with the complexation of NHC and enal to give the Breslow intermediate, which diverges afterward. Then, the azomethine imine can either react with the Breslow intermediate to give the six‐membered ring product or the β‐carbon protonation occurs for forming the enolate intermediate controlled by different bases. The formed enolate intermediate reacts with azomethine imine to afford the five‐membered ring product. The calculated results show that only the base K2CO3 can facilitate the structural transformation between homoenolate and enolate to switch the chemoselectivity; therefore, the [3+3] annulation happens preferentially in the presence of base DBU while the other situation occurs with K2CO3 as base. The NCI analysis results reveal that the stereoselectivity is predominately determined by the π???π, C?H???O, and C?H???N interactions. The obtained mechanistic insights should provide valuable clues for the rational design of these kinds of divergent reactions. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(4):1046-1050
Two new gold‐catalyzed annulations of isoxazoles with propiolates have been developed. Most isoxazoles follow an initial O attack on the alkyne to afford a [4+1] annulation product. This process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through an N attack step to yield formal [2+2+1]/[4+2] annulation products. These two annulation products arise initially from two seven‐membered heterocyclic intermediates, which then lead to products. 相似文献
11.
In contrast with the reported phosphine‐ and DABCO‐catalyzed [3+2] and [2+2] annulation of allenoates with trifluoromethylketone, the [2+2+2] annulation of allenoates and two molecules of trifluoromethylketone was found under the condition of N‐heterocyclic carbene catalysis. 相似文献
12.
Zhi‐Qin Liang Zhong‐Hua Gao Wen‐Qiang Jia Prof. Dr. Song Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1868-1872
Bifunctional N‐heterocyclic carbenes with a free hydroxy group are demonstrated as efficient catalysts for the [3+4] annulation of enals with aurones to give the corresponding benzofuran‐fused ε‐lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Control experiments reveal that the [3+4] cycloadducts are kinetically favored and could be transformed to the thermodynamically favored [3+2] cycloadducts with a non‐bifunctional NHC catalyst. 相似文献
13.
《中国化学快报》2022,33(12):5128-5131
The electrooxidative [3 + 2] annulation of amidines with 2-arylideneindane-1,3-diones or 4-alkylidene pyrazolones is reported using NaI as a redox catalyst and electrolyte under constant current electrolysis in an undivided cell. The current strategy features excellent functional group tolerance, simple operation, and mild conditions, thus providing an environmentally benign and efficient access to spiroimidazolines in moderate to good yields. 相似文献
14.
Unusual Formal [1+4] Annulation through Tandem P(NMe2)3‐Mediated Cyclopropanation/Base‐Catalyzed Cyclopropane Rearrangement: Facile Syntheses of Cyclopentenimines and Cyclopentenones 下载免费PDF全文
Dr. Rong Zhou Kai Zhang Ling Han Yusong Chen Prof. Dr. Ruifeng Li Prof. Dr. Zhengjie He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5883-5887
An unusual formal [1+4] annulation of α‐dicarbonyl compounds with 1,1‐dicyano‐1,3‐dienes has been realized, leading to facile syntheses of cyclopentenimines and cyclopentenones in a unique manner. Mechanistic investigation implies that this reaction takes place through a P(NMe2)3‐mediated cyclopropanation followed by a base‐catalyzed cyclopropane rearrangement. It therefore represents an unprecedented [1+4] annulation mode involving Kukhtin–Ramirez adducts. 相似文献
15.
Phosphine‐Catalyzed Annulations of 4,4‐Dicyano‐2‐Methylenebut‐3‐enoates with Maleimides and Maleic Anhydride 下载免费PDF全文
Xiao‐Nan Zhang Gen‐Qiang Chen Dr. Xiang‐Ying Tang Dr. Yin Wei Dr. Min Shi 《Angewandte Chemie (International ed. in English)》2014,53(40):10768-10773
A novel phosphine‐catalyzed [4+1] annulation of maleimides with 4,4‐dicyano‐2‐methylenebut‐3‐enoates has been developed to afford spirocyclic products, and the maleimides serves as C1 synthons. Moreover, a phosphine‐catalyzed formal [3+2] annulation between 4,4‐dicyano‐2‐methylenebut‐3‐enoates and maleic anhydride has been also achieved, and maleic anhydride behaved as a C3 synthon in the reaction, thus efficiently affording the functionalized cyclopentenones. A stable phosphinium‐containing zwitterionic compound is the key reactive intermediate in both annulations and was successfully isolated. Plausible mechanisms have been proposed on the basis of control experiments and deuterium‐labeling experiments. 相似文献
16.
Rhodium(III)‐Catalyzed [3+2] Annulation of 5‐Aryl‐2,3‐dihydro‐1H‐pyrroles with Internal Alkynes through C(sp2)H/Alkene Functionalization 下载免费PDF全文
Ming‐Bo Zhou Rui Pi Ming Hu Yuan Yang Ren‐Jie Song Dr. Yuanzhi Xia Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(42):11338-11341
This study describes a new rhodium(III)‐catalyzed [3+2] annulation of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp2)? H bond and addition/protonolysis of an alkene C?C bond. This method is applicable to a wide range of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles and internal alkynes, and results in the assembly of the spiro[indene‐1,2′‐pyrrolidine] architectures in good yields with excellent regioselectivities. 相似文献
17.
Chunlan Song Xin Dong Zhongjie Wang Kun Liu Chien‐Wei Chiang Aiwen Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12334-12338
The [4+2] annulation represents an elegant and versatile synthetic protocol for the construction of benzene rings. Herein, a strategy for visible‐light induced [4+2] annulation of thiophenes and alkynes, to afford benzene rings, is presented. Under simple and mild reaction conditions, the ready availability and structural diversity of thiophenes and alkynes permit the facile synthesis of several substituted aromatic rings. Valuable drugs and amino acids are also well tolerated. Moreover, DFT calculations explain the high regioselectivity of the reaction. 相似文献
18.
Houhua Li Rajesh Gontla Jana Flegel Christian Merten Slava Ziegler Andrey P. Antonchick Herbert Waldmann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):313-317
Herein, we report the first enantioselective annulation of α‐arylidene pyrazolones through a formal C(sp3)?H activation under mild conditions enabled by highly variable RhIII‐Cpx catalysts. The method has a wide substrate scope and proceeds with good to excellent yields and enantioselectivities. Its synthetic utility was demonstrated by the late‐stage functionalization of drugs and natural products as well as the preparation of enantioenriched [3]dendralenes. Preliminary biological investigations also identified the spiropyrazolones as a novel class of Hedgehog pathway inhibitors. 相似文献
19.
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
20.
Erqing Li Prof. Dr. You Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3520-3527
A novel strategy that involves phosphine‐catalyzed sequential [2+3] and [3+2] annulation reactions was developed. In this domino reaction, γ‐substituted allenoates were used as novel C4 synthons, and the bicyclic cyclopenta[b]dihydrofuran derivatives were produced in good to excellent diastereoselectivities and yields under mild conditions. Furthermore, preliminary studies on an asymmetric variant of this reaction proceeded with moderate enantioselectivity. 相似文献