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1.
Convenient Synthesis of 2‐Amino‐4H‐chromenes from Photochemically Generated o‐Quinone Methides and Malononitrile
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Makoto Fujiwara Masanori Sakamoto Kimihiro Komeyama Hiroto Yoshida Ken Takaki 《Journal of heterocyclic chemistry》2015,52(1):59-66
2‐Amino‐4H‐chromenes were synthesized in moderate to good yields by the reaction of o‐quinone methides photochemically generated from o‐(dimethylaminomethyl)phenols with malononitrile. This method was applicable to the synthesis of fluorinated chromenes that were difficult to obtain by other methods. In addition, o‐(hydroxymethyl)phenols could be used for the reaction in the presence of tertiary amine bases. 相似文献
2.
Catalytic Asymmetric Addition of Meldrum’s Acid,Malononitrile, and 1,3‐Dicarbonyls to ortho‐Quinone Methides Generated In Situ Under Basic Conditions
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Lorenzo Caruana Martina Mondatori Vasco Corti Sara Morales Prof. Andrea Mazzanti Prof. Mariafrancesca Fochi Prof. Luca Bernardi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6037-6041
A new approach to the utilization of highly reactive and unstable ortho‐quinone methides (o‐QMs) in catalytic asymmetric settings is presented. The enantioselective reactions are catalysed by bifunctional organocatalysts, and the o‐QM intermediates are formed in situ from 2‐sulfonylalkyl phenols through base‐promoted elimination of sulfinic acid. The use of mild Brønsted basic conditions for transiently generating o‐QMs in catalytic asymmetric processes is unprecedented, and allows engaging productively in the reactions nucleophiles such as Meldrum’s acid, malononitrile and 1,3‐dicarbonyls. The catalytic transformations give new and general entries to 3,4‐dihydrocoumarins, 4H‐chromenes and xanthenones. These frameworks are recurring structures in natural product and medicinal chemistry, as testified by the formal syntheses of (R)‐tolterodine and (S)‐4‐methoxydalbergione from the catalytic adducts. 相似文献
3.
Meng Sun Chun Ma Si‐Jia Zhou Sai‐Fan Lou Jian Xiao Yinchun Jiao Feng Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8795-8800
The first catalytic asymmetric (4+3) cyclization of in situ generated ortho‐quinone methides with 2‐indolylmethanols has been established, which constructed seven‐membered heterocycles in high yields (up to 95 %) and excellent enantioselectivity (up to 98 %). This approach not only represents the first catalytic asymmetric (4+3) cyclization of o‐hydroxybenzyl alcohols, but also enabled an unprecedented catalytic asymmetric (4+3) cyclization of 2‐indolylmethanols. In addition, a scarcely reported catalytic asymmetric (4+3) cyclization of para‐quinone methide derivatives was accomplished. 相似文献
4.
Brønsted Acid‐Catalyzed,Highly Enantioselective Addition of Enamides to In Situ‐Generated ortho‐Quinone Methides: A Domino Approach to Complex Acetamidotetrahydroxanthenes
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Dr. Satyajit Saha Prof. Dr. Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2348-2352
The highly enantioselective conjugate addition of enamides and enecarbamates to in situ‐generated ortho‐quinone methides, upon subsequent N,O‐acetalization, gives rise to acetamido‐substituted tetrahydroxanthenes with generally excellent enantio‐ and diastereoselectivities. A chiral BINOL‐based phosphoric acid catalyst controls the enantioselectivity of the carbon–carbon bond‐forming event. The products are readily converted into other xanthene‐based heterocycles. 相似文献
5.
Chiral N,N′‐Dioxide–Scandium(III) Complex‐Catalyzed Asymmetric Friedel–Crafts Alkylation Reaction of ortho‐Hydroxybenzyl Alcohols with C3‐Substituted N‐Protected Indoles
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Jianfeng Zheng Dr. Lili Lin Li Dai Xiao Yuan Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18254-18258
The first Lewis acid catalyzed asymmetric Friedel–Crafts alkylation reaction of ortho‐hydroxybenzyl alcohols with C3‐substituted indoles is described. A chiral N,N′‐dioxide Sc(OTf)3 complex served not only to promote formation of ortho‐quinone methides (o‐QMs) in situ but also induced the asymmetry of the reaction. This methodology enables a novel activation of ortho‐hydroxybenzyl alcohols, thus affording the desired chiral diarylindol‐2‐ylmethanes in up to 99 % yield and 99 % ee. A range of functional groups were also tolerated under the mild reaction conditions. Moreover, this strategy gives concise access to enantioenriched indole‐fused benzoxocines. 相似文献
6.
Rameshwar Prasad Pandit Seung Tae Kim Do Hyun Ryu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13561-13566
A cyclopropanation/intramolecular rearrangement initiated by the Michael addition of in situ generated ortho‐quinone methides (o‐QMs) has been developed for the enantioselective synthesis of 2‐aryl‐2,3‐dihydrobenzofurans containing two consecutive stereogenic centers, including a quaternary carbon atom. In the presence of a chiral oxazaborolidinium ion catalyst, the reaction proceeded in excellent yields (up to 95 %) with excellent stereoselectivity (up to >99 ee, up to >20:1 d.r.). 相似文献
7.
Arun Suneja Henning Jakob Loui Christoph Schneider 《Angewandte Chemie (International ed. in English)》2020,59(14):5536-5540
We describe herein a highly diastereo‐ and enantioselective [4+3]‐cycloannulation of ortho‐quinone methides and carbonyl ylides to furnish functionalized oxa‐bridged dibenzooxacines with excellent yields and stereoselectivity in a single synthetic step. The combination of rhodium and chiral phosphoric acid catalysis working in concert to generate both transient intermediates in situ provides direct access to complex bicyclic products with two quaternary and one tertiary stereogenic centers. The products may be further functionalized into valuable and enantiomerically highly enriched building blocks. 相似文献
8.
Synergistic Rhodium/Phosphoric Acid Catalysis for the Enantioselective Addition of Oxonium Ylides to ortho‐Quinone Methides
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Dr. Santosh Kumar Alamsetti M. Sc. Matthias Spanka Prof. Dr. Christoph Schneider 《Angewandte Chemie (International ed. in English)》2016,55(7):2392-2396
We report herein a powerful and highly stereoselective protocol for the domino‐type reaction of diazoesters with ortho‐quinone methides generated in situ to furnish densely functionalized chromans with three contiguous stereogenic centers. A transition‐metal and a Brønsted acid catalyst were shown to act synergistically to produce a transient oxonium ylide and ortho‐quinone methide, respectively, in two distinct cycles. These intermediates underwent subsequent coupling in a conjugate‐addition–hemiacetalization event in generally good yield with excellent diastereo‐ and enantioselectivity. 相似文献
9.
Organocatalytic Domino Oxa‐Michael/1,6‐Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds
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Kun Zhao Dr. Ying Zhi Tao Shu Dr. Arto Valkonen Prof. Dr. Kari Rissanen Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2016,55(39):12104-12108
An asymmetric organocatalytic domino oxa‐Michael/1,6‐addition reaction of ortho‐hydroxyphenyl‐substituted para‐quinone methides and isatin‐derived enoates has been developed. In the presence of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4‐phenyl‐substituted chromans bearing spiro‐connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee). 相似文献
10.
Catalytic Asymmetric 1,6‐Conjugate Addition of para‐Quinone Methides: Formation of All‐Carbon Quaternary Stereocenters
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Dr. Zhaobin Wang Yuk Fai Wong Prof. Jianwei Sun 《Angewandte Chemie (International ed. in English)》2015,54(46):13711-13714
Described herein is a general and mild catalytic asymmetric 1,6‐conjugate addition of para‐quinone methides (p‐QMs), a class of challenging reactions with previous limited success. Benefiting from chiral Brønsted acid catalysis, which allows in situ formation of p‐QMs, our reaction expands the scope to general p‐QMs with various substitution patterns. It also enables efficient intermolecular formation of all‐carbon quaternary stereocenters with high enantioselectivity. 相似文献
11.
A highly enantioselective three‐component hydroacyloxylation/1,4‐conjugate addition of ortho‐hydroxybenzyl alcohols, ynamides and carboxylic acids was developed under mild reaction conditions in the presence of a chiral N,N′‐dioxide/Sc(OTf)3 complex, which went through in situ generated ortho‐quinone methides with α‐acyloxyenamides, delivering a range of corresponding chiral α‐acyloxyenamides derivatives containing gem(1,1)‐diaryl skeletons in moderate to good yields with excellent ee values. The scale‐up experiment and further derivation showed the practicality of this catalytic system. In addition, a possible catalytic cycle and transition state model was proposed to elucidate the origin of the stereoselectivity based on X‐ray crystal structure of the α‐acyloxyenamide intermediate and product. 相似文献
12.
Triflic Acid Mediated Cascade Cyclization of Aryldiynes for the Synthesis of Indeno[1,2‐c]chromenes: Application to Dye‐Sensitized Solar Cells
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Hua Jiang Dr. Giovanni Ferrara Xuan Zhang Kazuaki Oniwa Dr. Ashraful Islam Dr. Liyuan Han Dr. Ying‐Ji Sun Ming Bao Dr. Naoki Asao Dr. Yoshinori Yamamoto Dr. Tienan Jin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4065-4070
A new triflic acid (TfOH)‐mediated cascade cyclization of ortho‐anisole‐substituted aryldiynes is described for the construction of indeno[1,2‐c]chromenes. The cascade cyclization proceeds through an unusual TfOH‐induced alkyne‐alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho‐aniline‐ or ortho‐thioanisole‐substituted aryldiynes. A new class of organic dyes with the indeno[1,2‐c]chromene framework as both donor and π‐linker were synthesized. These compounds exhibit high photovoltaic performances in dye‐ sensitized solar cells (DSCs). 相似文献
13.
Patrick Kempe Dr. Tina Löschner Prof. Alexander A. Auer Dr. Andreas Seifert Dr. Gerhard Cox Prof. Dr. Stefan Spange 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8040-8053
The twin monomer 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] ( 1 ) can be polymerized to nanostructured SiO2/phenolic‐resin composite material by thermally induced twin polymerization. Thermally induced twin polymerization represents a way to produce nanocomposites simply by thermal induction of twin monomers. Besides 1 , the thermal reaction of several related salicylic (2‐oxybenzylic) silicon molecules has been investigated. The thermal cleavage of the molecules is studied by using several trapping reagents (e.g., vinyl compounds). A significant occurrence of quinone methide adducts indicates that the thermal mechanism proceeds not only by a ring opening at the oxymethylene position, but also with the ortho‐quinone methide as a central or alternative intermediate. This is supported by product analyses of thermally initialized reactions of 1 and its substituted analogues as well as by quantum chemical calculations. 相似文献
14.
Djamila Hikem‐Oukacha Maamar Hamdi Artur M. S. Silva Rachedi Yahia 《Journal of heterocyclic chemistry》2011,48(1):63-68
3‐(Bromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one was synthesized by the reaction of dehydroacetic acid (DHAA) with bromine in glacial acetic acid. Novel heterocyclic products were synthesized from the reaction of bromo‐DHAA with alkanediamines, phenylhydrazines, ortho‐phenylenediamines, and ortho‐aminobenzenethiol. The obtained new products 3‐(2‐N‐substituted‐acetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐ones, 4‐hydroxy‐3‐[1‐hydroxy‐2‐(2‐phenylhydrazinyl)vinyl]‐6‐methyl‐2H‐pyran‐2‐one, 1‐(2,4‐dinitrophenyl)‐7‐methyl‐2,3‐dihydro‐1H‐pyrano[4,3‐c]pyridazine‐4,5‐dione, 3‐(3,4‐dihydroquinoxalin‐2‐yl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one/3‐(3,4‐dihydroquinoxalin‐2‐yl)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione, 6‐methyl‐3‐(3,4‐dihydroquinoxalin‐2‐yl)‐2H‐pyran‐2,4(3H)‐dione, and (E)‐3‐(2H‐benzo[b][1,4]thiazin‐3(4H)‐ylidene)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione were fully characterized by IR, 1H and 13C NMR, and mass spectra. J. Heterocyclic Chem., 2011. 相似文献
15.
Ali Aminkhani Mina Talati Roholah Sharifi Firouzeh Chalabian Fatemeh Katouzian 《Journal of heterocyclic chemistry》2019,56(6):1812-1819
A remarkably efficient three‐component reaction to synthesize 2‐amino‐4H‐chromenes derivatives from malononitrile, various aromatic aldehydes, and orcinol was described at room temperature in CH2Cl2 in the presence of catalytic amount of triethylamine. In a facile one‐pot procedure, excellent yields of products were achieved in less than 1 h. Some of the synthesized 2‐amino‐4H‐chromenes derivatives demonstrated potent antibacterial activities against Gram‐positive bacteria including Staphylococcus aureus and Bacillus anthracis, indicated by disk method, minimum inhibitory concentration, and minimum bactericidal concentration approaches. However, none of the tested compounds expressed any antibacterial activities against Enterococcus faecalis and Gram‐negative bacteria. 相似文献
16.
Catalytic Asymmetric Cycloaddition of In Situ‐Generated ortho‐Quinone Methides and Azlactones by a Triple Brønsted Acid Activation Strategy
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Xiao‐Ye Yu Prof. Dr. Jia‐Rong Chen Qiang Wei Hong‐Gang Cheng Zhi‐Cheng Liu Prof. Dr. Wen‐Jing Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6774-6778
A convergent and highly stereoselective [4+2] cycloaddition of in situ‐generated ortho‐Quinone methides (o‐QMs) and azlactone enols has been successfully developed through a triple Brønsted acid catalysis strategy. This protocol provides an efficient and mild access to various densely functionalized dihydrocoumarins bearing adjacent quaternary and tertiary stereogenic centers in high yields with excellent diastereo‐ and enantioselectivity. 相似文献
17.
《Angewandte Chemie (International ed. in English)》2017,56(18):4936-4940
Herein, we describe the first catalytic asymmetric intramolecular [4+2] cycloaddition of in situ generated ortho‐quinone methides. In the presence of a confined chiral imidodiphosphoric acid catalyst, various salicylaldehydes react with dienyl alcohols to give transient ortho ‐quinone methide intermediates, which undergo an intramolecular [4+2] cycloaddition to provide highly functionalized furanochromanes and pyranochromanes in excellent diastereoselectivity and enantioselectivity. 相似文献
18.
Dr. Michael P. Boone Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3333-3341
The reactivity of [{(Ph2PC6H4)2B(η6‐Ph)}RuCl][B(C6F5)4] ( 1 ) as a Lewis acid was investigated. Treatment of 1 with mono and multidentate phosphorus Lewis bases afforded the Lewis acid–base adducts with the ortho‐carbon atom of the coordinated arene ring. Similar reactivity was observed upon treatment with N‐heterocyclic carbenes; however, adduct formation occurred at both ortho‐ and para‐carbon atoms of the bound arene with the para‐position being favoured by increased steric demands. Interestingly treatment with isocyanides resulted in adduct formation with the B‐centre of the ligand framework. The hydride‐cation [{(Ph2PC6H4)2B(η6‐Ph)}RuH] [B(C6F5)4] was prepared via reaction of 1 with silane. This species in the presence of a bulky phosphine behaves as a frustrated Lewis pair (FLP) to activate H2 between the phosphorus centre and the ortho‐carbon atom of the η6‐arene ring. 相似文献
19.
A series of dimethyl 6‐aryl‐2,2‐dimethyl‐2H‐chromene‐7,8‐dicarboxylates were synthesized, and the photochromic properties of this new family of dimethyl‐2H‐chromenes were studied under continuous irradiation. The presence of the methoxycarbonyl groups was shown to stabilize the colored forms. This stabilization depended on the solvent, and in two cases the formation of long‐lived opened forms was observed. Under irradiation with a mercury lamp, this family of 2H‐chromenes showed a strong resistance to photodegradation. 相似文献
20.
Phosphoric Acid Catalyzed Asymmetric 1,6‐Conjugate Addition of Thioacetic Acid to para‐Quinone Methides
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Nan Dong Zhi‐Pei Zhang Dr. Xiao‐Song Xue Prof. Xin Li Prof. Jin‐Pei Cheng 《Angewandte Chemie (International ed. in English)》2016,55(4):1460-1464
An asymmetric 1,6‐conjugate addition of thioacetic acid with para‐quinone methides has been developed by using chiral phosphoric acid catalysis in the presence of water. A series of sulfur‐containing compounds were thus obtained in high yields with good to excellent enantioselectivities. Theoretical studies indicated that the water‐bridged proton transfer is a potentially favorable reaction pathway. An unprecedented O?H???π interaction between water and the aromatic nucleus of chiral phosphoric acid was discovered to contribute significantly to the stereocontrol in the catalysis. 相似文献