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1.
Kunal Kumar Jha Sanjay Dutta Saibal Sar Subhabrata Sen Parthapratim Munshi 《Tetrahedron》2018,74(51):7326-7334
Presence of cyclobutane rings in bioactive natural products makes them a popular synthetic target. Most common strategy for synthesizing cyclobutanes is [2+2] cycloaddition, which is usually facilitated by using ultraviolet radiation and catalysts. Herein we report the design and synthesis of densely functionalized cyclobutanes by alleviating these drawbacks and using sunlight. Further, we identified the putative mechanism of the transformation based on kinetic, fluorescence and crystallographic studies and evaluated biological activities of the products against MCF7 cell lines. The rational design of the olefinic substrates was based on their UV–vis spectra. The generic aspect of the reaction was elucidated by the syntheses of diverse analogs of cyclobutanes. Further, crystal structures and UV–vis spectra of the olefinic partners assisted us in rationalizing the stereoselectivity of the heterodimers. We believe this energy-efficient mild approach will provide a substantial contribution to the existing repertoire of strategies to regio- and stereoselectively access cyclobutanes. 相似文献
2.
Enantioselective Synthesis of Cyclobutylboronates via a Copper‐Catalyzed Desymmetrization Approach
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Dr. Manuel Guisán‐Ceinos Dr. Alejandro Parra Víctor Martín‐Heras Dr. Mariola Tortosa 《Angewandte Chemie (International ed. in English)》2016,55(24):6969-6972
The first catalytic enantioselective synthesis of cyclobutylboronates, by using a chiral copper(I) complex, is reported. A broad variety of cyclobutanes have been prepared with consistently high levels of diastereo‐ and enantiocontrol. Moreover, this method constitutes the first report of an enantioselective desymmetrization of meso‐cyclobutenes to prepare chiral cyclobutanes. 相似文献
3.
Li‐Li Ma Yuan‐Yuan An Li‐Ying Sun Yao‐Yu Wang F. Ekkehardt Hahn Ying‐Feng Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4026-4031
A new class of supramolecular metallacycles capable of undergoing photochemical reactions and in situ release of cyclobutanes in solution is described. The molecular metallacycles were generated through coordination‐driven self‐assembly of dinuclear metal‐carbene complexes as organometallic clips with olefin‐functionalized bridging ligands. Photolysis of these molecular metallacycles in situ led to structural interconversion and release of the formed cyclobutane products with quantitative conversion. Further modifications of the obtained cyclobutanes provided a series of new species containing the cyclobutane skeleton. 相似文献
4.
Asymmetric Organocatalytic Stepwise [2+2] Entry to Tetra‐Substituted Heterodimeric and Homochiral Cyclobutanes
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Alex J. Nielsen Dr. Hilary A. Jenkins Dr. James McNulty 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9111-9115
An asymmetric synthesis of tetra‐substituted cyclobutanes involving an organocatalytic, stepwise [2+2]‐cycloaddition is described. The secondary‐amine‐catalyzed method allows for the hetero‐dimerization of two different cinnamic‐acid‐derived sub‐units, opening a novel one‐step assembly to densely functionalized, head‐to‐tail coupled dimeric cyclobutanes in high enantiomeric excess. A series of selective synthetic interconversions in these sensitive cycloadducts is also described. 相似文献
5.
A facile CAN-mediated oxidative rearrangement of alkoxyaryl cyclobutanes and oxetanes is described. 相似文献
6.
Yongshun Wen Meizhen Liu Prof. Zuliang Chen Yingjing Wei 《European journal of organic chemistry》2023,26(38):e202300845
A mild and straightforward access to various substituted naphthalene-fused oxepines from readily available Donor-Acceptor (D-A) cyclobutanes is reported. This method involves the Lewis acid-catalyzed reactions of D-A cyclobutanes with 2-naphthols to afford ring-opened products, which can undergo intramolecular cyclization mediated by the NBS-base system to yield corresponding naphthalene-fused oxepines. The cyclization protocol involves a nucleophilic attack of the oxygen of 2-naphthol on the newly formed electrophilic acceptor end of D-A cyclobutane. 相似文献
7.
R. J. Abraham M. A. Cooper J. R. Salmon D. Whittaker 《Magnetic resonance in chemistry : MRC》1972,4(4):489-507
The PMR spectra of twelve pinene derivatives are reported, analysed and assigned. The proton couplings in the bridged cyclobutane group are compared with those of other strained cyclobutanes, and the relationship between 2JHH and the C.CH2.C angle is shown to be anomalous in these systems, suggesting unusually small H. C. H. angles in cyclobutanes. The very large values of 4JHH (eq-eq) in buckled cyclobutanes are interpreted in terms of current M. O. theory and also given a simple geometric rationalisation based on the direct mechanism. The various couplings in the pinene skeleton are discussed in terms of present theories and minor conformational effects in these molecules. Substituent chemical shift (SCS) values for Me and OH groups around the pinene skeleton are obtained, and shown not to agree with calculations based on present theories of chemical shifts. 相似文献
8.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(48):15609-15612
[2+2] Photocycloaddition, for example, the dimerization of chalcones and cinnamic acid derivatives, is a unique strategy to construct cyclobutanes, which are building blocks for a variety of biologically active molecules and natural products. However, most attempts at the above [2+2] addition have focused on solid‐state, molten‐state, or host–guest systems under ultraviolet‐light irradiation in order to overcome the competition of facile geometric isomerization of nonrigid olefins. We report a general and simple method to realize the intermolecular [2+2] dimerization reaction of these acyclic olefins to construct cyclobutanes in a highly regio‐ and diastereoselective manner in solution under visible light, which provides an efficient solution to a long‐standing problem. 相似文献
9.
Yao Xu Michael L. Conner Prof. M. Kevin Brown 《Angewandte Chemie (International ed. in English)》2015,54(41):11918-11928
Cyclobutanes and cyclobutenes are important structural motifs found in numerous biologically significant molecules, and they are useful intermediates for chemical synthesis. Consequently, [2+2] cycloadditions to access cyclobutanes and cyclobutenes have been established to be particularly useful transformations. Within the last 10 years, an increase in the frequency of publications for catalytic enantioselective [2+2] cycloadditions has occurred. These reactions provide access to a wide array of enantiomerically enriched chemical diversity that was not previously attainable. Described in this review are the advances made in catalytic enantioselective [2+2] cycloadditions to access cyclobutanes and cyclobutenes. 相似文献
10.
A copper catalyzed stereoselective [2+2] cyclization has been developed, providing a concise protocol to the direct construction of diaryl‐substituted cyclobutanes in up to 99% yield with up to >95/5 dr. Meanwhile, the enantioselective version of this reaction has also been achieved, leading to a series of optically active diaryl‐substituted cyclobutanes with up to 94% ee. 相似文献
11.
Dr. Guillaume Ernouf Dr. Egor Chirkin Dr. Lydia Rhyman Dr. Ponnadurai Ramasami Dr. Jean-Christophe Cintrat 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(7):2640-2644
A new photoredox-catalyzed decarboxylative radical addition approach to functionalized cyclobutanes is described. The reaction involves an unprecedented formal Giese-type addition of C(sp3)-centered radicals to highly strained bicyclo[1.1.0]butanes. The mild photoredox conditions, which make use of a readily available and bench stable phenyl sulfonyl bicyclo[1.1.0]butane, proved to be amenable to a diverse range of α-amino and α-oxy carboxylic acids, providing a concise route to 1,3-disubstituted cyclobutanes. Furthermore, kinetic studies and DFT calculations unveiled mechanistic details on bicyclo[1.1.0]butane reactivity relative to the corresponding olefin system. 相似文献
12.
Honda K Konishi M Kawai M Yamada A Takahashi Y Hoshino Y Inoue S 《Natural product communications》2012,7(4):459-462
Optically active 1,3-bridged cyclobutanes 10 of the bicyclo[3.1.1]heptane ring system and 1,2-bridged cyclobutanes 11 of the bicyclo[3.2.0]heptane ring system were produced by UV irradiation of alpha,beta,gamma,delta-unsaturated esters 9a and 9c-f. The preference of endo-stereochemistry at C-6 bridged head was observed in cross-adducts 10. On the other hand, irradiation of conjugated dienol 9b led via only parallel cycloaddition to 1,2-bridged cyclobutane 11. 相似文献
13.
Francesca R CibinNicoletta Di Bello Giancarlo Doddi Vincenzo Fares Paolo Mencarelli Elio Ullucci 《Tetrahedron》2003,59(50):9971-9978
The intramolecular photocycloaddition of chalcones to give cyclobutanes has proved to be a fast and convenient method to shrink a cyclophane ring to a tricyclic system, in order to prepare potential ditopic receptors. X-Ray results confirm the previously indicated structure for the cyclobutanes 2a (n=1, m=1), in which the cyclization occurs by a head-to-head syn ring closure. NMR results indicate that the same process occurs for the cyclobutanes 2b (n=2, m=2) and 2c (n=1, m=3). 相似文献
14.
Guillaume Ernouf Egor Chirkin Lydia Rhyman Ponnadurai Ramasami Jean‐Christophe Cintrat 《Angewandte Chemie (International ed. in English)》2020,59(7):2618-2622
A new photoredox‐catalyzed decarboxylative radical addition approach to functionalized cyclobutanes is described. The reaction involves an unprecedented formal Giese‐type addition of C(sp3)‐centered radicals to highly strained bicyclo[1.1.0]butanes. The mild photoredox conditions, which make use of a readily available and bench stable phenyl sulfonyl bicyclo[1.1.0]butane, proved to be amenable to a diverse range of α‐amino and α‐oxy carboxylic acids, providing a concise route to 1,3‐disubstituted cyclobutanes. Furthermore, kinetic studies and DFT calculations unveiled mechanistic details on bicyclo[1.1.0]butane reactivity relative to the corresponding olefin system. 相似文献
15.
Transmetalation of carborane-fused zirconacycles to Cu(Ⅱ) induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carborane-fused cyclobutenes and cyclobutanes. A reaction mechanism involving transmetalation to Cu(Ⅱ) and reductive elimination is proposed. 相似文献
16.
EricJ. May AnneBuyle Padias RobertB. Bates HenryK. Hall 《Helvetica chimica acta》2005,88(6):1397-1404
Bifunctional vinyl ethers react with electron‐poor alkenes to cyclobutanes in good yields. The second C?C bond reacted with neither the cyclobutane nor its zwitterion intermediate, even on heating. Cyclobutanes formed from ‘tetracyanoethylene’ ( 8 ) were transformed into tetrahydropyridines by reaction of the corresponding zwitterion with MeCN as the solvent. In contrast, cyclobutanes formed from dimethyl (dicyanomethylidene)propanedioate ( 9 ) did not react with MeCN, which is ascribed to diminished stabilization of the zwitterion intermediate, and increased steric effects. These results extend the classical studies of Huisgen and his co‐workers. 相似文献
17.
The corresponding diamides were obtained from reaction of cis-3-carboxy-2,2-dimethylcyclobutylacetic acid (pinic acid) and of cis/trans-3-(carboxymethyl)-2,2-dimethylcyclobutylacetic acid (homopinic acid) dichlorides with two equivalents of 5-bromo-, 4-chloro-, and 4,5-dimethoxyanthranilic acids. Treatment of them with formamide leads to the formation of the corresponding 2,2-dimethyl-3-[4(3H)-oxo-2-quinazolinyl]methyl-1-[4(3H)-oxo-2-quinazolinyl]cyclobutanes and 2,2-dimethyl-1,3-di[4(3H)-oxo-2-quinazolinylmethyl]cyclobutanes. 相似文献
18.
Klärner FG Wurche F Doering Wv Yang J 《Journal of the American Chemical Society》2005,127(51):18107-18113
Pressure dependent rate constants and volumes of activation for stereomutational interconversions of the cyclobutanes, anti- and syn-2,9-dicyanodispiro[5.0.5.2]tetradeca-1,8-dienes (anti-6 and syn-6), and for their fragmentation to 1-cyano-3-methylenecyclohexene (5) have been determined. Although fragmentations might have been expected to have larger and thus more positive volumes of activation than stereomutation, both processes have essentially identical volumes of activation within experimental uncertainties at 50.1 degrees C over the pressure range, 1-3000 bar: DeltaV(not equal) = (+7.4 to +9.9) +/- 2.0 cm3 mol(-1). While these positive values are consistent with the rate of entry into the hypothetical caldera being determined by breaking the weakest bond in the cyclobutanes, the insensitivity of the product-determining exit channels argues against the obligatory second bond-breaking being a significant factor in fragmentation. 相似文献
19.
The formal [4+3] cycloaddition of 2-alkoxy-1,1-dicarboxylate activated donor-acceptor cyclobutanes with nitrones is disclosed. The reaction forms structurally unique oxazepines in moderate to high yield with a wide scope of nitrones. In most cases either a diastereomeric mixture or a single diastereomer may be formed, depending on the reaction conditions. 相似文献
20.
Diastereoselective synthesis of fulleropyrrolidines from suitably functionalized chiral cyclobutanes
Illescas BM Martín N Poater J Solà M Aguado GP Ortuño RM 《The Journal of organic chemistry》2005,70(17):6929-6932
The first diastereoselective synthesis of fulleropyrrolidines endowed with diastereomerically pure functionalized cyclobutanes is reported. The new C(60)-based cyclobutane derivatives 7a,b and 9 are suitably functionalized for further incorporation into peptide surrogates. 相似文献