- Catalytic Syn-Selective Nitroaldol Approach to Amphenicol Antibiotics: Evolution of a Unified Asymmetric Synthesis of (-)-Chloramphenicol, (-)-Azidamphenicol, (+)-Thiamphenicol, and (+)-Florfenicol
-
A unified strategy for an efficient and high diastereo- and enantioselective synthesis of (-)-chloramphenicol, (-)-azidamphenicol, (+)-thiamphenicol, and (+)-florfenicol based on a key catalytic syn-selective Henry reaction is reported. The stereochemistry of the ligand-enabled copper(II)-catalyzed aryl aldehyde Henry reaction of nitroethanol was first explored to forge a challenging syn-2-amino-1,3-diol structure unit with vicinal stereocenters with excellent stereocontrol. Multistep continuous flow manipulations were carried out to achieve the efficient asymmetric synthesis of this family of amphenicol antibiotics.
- Chen, Fener,Cheng, Dang,Huang, Huashan,Jiang, Meifen,Liu, Minjie,Qu, Hongmin,Xia, Yingqi,Xiong, Tong,Zhang, Yan
-
supporting information
p. 11557 - 11570
(2021/09/02)
-
- Efficient preparation method of symmetric diarylethene compound
-
The invention belongs to the technical field of fine chemicals and related chemistry, and provides an efficient preparation method of a symmetric diarylethene compound. The method comprises the following steps: with halomethyl-containing aromatic hydrocarbon and derivatives thereof as raw materials, conducting reacting at 100 DEG C for 12 hours in the presence of a catalyst, alkali, additives andan anhydrous organic solvent so as to obtain the corresponding diarylethene compound with symmetry. The method has the beneficial effects that no transition metal reaction exists, reaction conditionsare mild, operation is simple and convenient, the possibility of industrialization is realized, and the diarylethene compound is obtained at high yield; and the diarylethene compound synthesized by using the method can be further functionalized to obtain various compounds, and is applied to development and research of natural products, functional materials and fine chemicals.
- -
-
Paragraph 0059-0061
(2021/02/10)
-
- Selenenate Anions (PhSeO?) as Organocatalyst: Synthesis of trans-Stilbenes and a PPV Derivative
-
The selenenate anion (RSeO?) is introduced as an active organocatalyst for the dehydrohalogen coupling of benzyl halides to form trans-stilbenes. It is shown that RSeO? is a more reactive catalyst than the previously reported sulfur analogues (sulfenate anion, RSO?) and selenolate anions (RSe?) in the aforementioned reaction. This catalytic system was also applied to the benzylic-chloromethyl-coupling polymerization (BCCP) of a bis-chloromethyl arene to form ppv (poly(p-phenylene vinylene))-type polymers with high yields, Mn (average molecular weight) up to 13,000 and ? (dispersity) of 1.15. (Figure presented.).
- Zheng, Zhipeng,Trofymchuk, Oleksandra S.,Kurogi, Takashi,Varela, Elena,Mindiola, Daniel J.,Walsh, Patrick J.
-
supporting information
p. 659 - 666
(2020/01/02)
-
- Photoinitiated carbonyl-metathesis: Deoxygenative reductive olefination of aromatic aldehydes: Via photoredox catalysis
-
Carbonyl-carbonyl olefination, known as McMurry reaction, represents a powerful strategy for the construction of olefins. However, catalytic variants that directly couple two carbonyl groups in a single reaction are less explored. Here, we report a photoredox-catalysis that uses B2pin2 as terminal reductant and oxygen trap allowing for deoxygenative olefination of aromatic aldehydes under mild conditions. This strategy provides access to a diverse range of symmetrical and unsymmetrical alkenes with moderate to high yield (up to 83%) and functional-group tolerance. To follow the reaction pathway, a series of experiments were conducted including radical inhibition, deuterium labelling, fluorescence quenching and cyclic voltammetry. Furthermore, NMR studies and DFT calculations were combined to detect and analyze three active intermediates: a cyclic three-membered anionic species, an α-oxyboryl carbanion and a 1,1-benzyldiboronate ester. Based on these results, we propose a mechanism for the CC bond generation involving a sequential radical borylation, "bora-Brook" rearrangement, B2pin2-mediated deoxygenation and a boron-Wittig process.
- Wang, Shun,Lokesh, Nanjundappa,Hioe, Johnny,Gschwind, Ruth M.,K?nig, Burkhard
-
p. 4580 - 4587
(2019/05/14)
-
- Direct Conversion of Alcohols into Alkenes by Dehydrogenative Coupling with Hydrazine/Hydrazone Catalyzed by Manganese
-
We have developed unprecedented methods for the direct transformation of primary alcohols to alkenes in the presence of hydrazine, and for the synthesis of mixed alkenes by the reaction of alcohols with hydrazones. The reactions are catalyzed by a manganese pincer complex and proceed in absence of added base or hydrogen acceptors, liberating dihydrogen, dinitrogen, and water as the only byproducts. The proposed mechanism, based on preparation of proposed intermediates and control experiments, suggests that the transformation occurs through metal–ligand cooperative N?H activation of a hydrazone intermediate.
- Das, Uttam Kumar,Chakraborty, Subrata,Diskin-Posner, Yael,Milstein, David
-
supporting information
p. 13444 - 13448
(2018/09/14)
-
- Alkenylation of arenes using disubstituted ethynes by palladium/carboxylic acid catalysis
-
Palladium/carboxylic acid-catalyzed alkenylation of heteroarenes and electron-deficient arenes using alkynes underwent C(sp2)H bond activation in arene substrates to give the corresponding alkenylarenes straightforwardly. The versatility of this transformation is demonstrated by the double alkenylation of functionalized thiophenes and 5,6-difluorobenzothiadiazole with alkynes and provides a one-step access to vinylenearylene- vinylene units.
- Minami, Yasunori,Furuya, Yuki,Kodama, Tatsuro,Hiyama, Tamejiro
-
supporting information
p. 674 - 677
(2018/04/30)
-
- Method for preparing trans-diphenylethylene compound
-
The invention relates to a preparation method of organic compounds and provides a method for preparing a trans-diphenylethylene compound. The method comprises adding a gem-dibromomethyl aromatic hydrocarbon compound, copper and polyamine into a reactor in the presence of a solvent, carrying out deoxidizing treatment, adding an oxygen-free water-free solvent into the reactor, carrying out a coupling reaction process to obtain C-C- double bonds, and carrying out separation and purification to obtain the trans-diphenylethylene compound. The method has mild synthesis conditions and has good reaction compatibility to different functional groups. The gem-dibromomethyl aromatic hydrocarbon compound as a raw material is easy to synthesize, may have different substituent groups and has a variable structure. The product obtained by coupling a raw material can be simply treated and has high purity. The asymmetric trans-diphenylethylene compound can be prepared from two different raw materials.
- -
-
Paragraph 0096; 0097; 0098; 0099; 0100; 0101; 0107
(2017/09/01)
-
- E-Stilbene derivatives synthesized by stereoselective reductive coupling of benzylic gem-dibromide promoted by Cu/polyamine
-
Stereoselective reductive coupling reaction of benzylic gem-dibromide promoted by Cu/polyamine produces E-stilbene derivatives with high yield under mild conditions. It provides a short pathway to synthesize symmetrical and asymmetrical E-stilbene derivatives using cheap reagents and alkenyl-free starting material together with easy workup.
- Cao, Hua,Wang, Qi
-
p. 2703 - 2706
(2017/06/23)
-
- T-shaped and H-shaped polymers constructed from UV-induced strain promoted azide-alkyne cycloaddition reaction
-
Topological polymers with T-shaped and H-shaped molecular architecture were built on the combination of atom transfer radical polymerization (ATRP) and UV-induced strain promoted azide-alkyne cycloaddition (SPAAC) reaction. In the presence of a cycloprope
- Zhu, Wen,Li, Zi,Sun, Peng,Ren, Lixia,Zhang, Ke
-
supporting information
p. 1 - 7
(2016/02/03)
-
- Palladium-Catalyzed Domino Process: Synthesis of Symmetrical Diarylalkynes, cis- and trans-Alkenes using Lithium Acetylide as a Synthon
-
An efficient domino protocol has been developed for the synthesis of symmetrical diarylalkynes. Notably, the method was successful in the presence of a palladium catalyst without the support of a copper co-catalyst. Significantly, the method enabled the use of the commercially available and cheap lithium acetylide ethylenediamine complex as a source of acetylene for the construction of dual C-C bonds, with a wide range of compatibility towards various substituents of the aryl bromides/iodides. Significantly, this protocol was successfully applied to the synthesis of cis- and trans-alkenes in a highly stereoselective manner in a sequential one-pot process.
- Krishna, Jonnada,Krishna Reddy, Alavala Gopi,Satyanarayana, Gedu
-
p. 3597 - 3610
(2016/01/25)
-
- Well-defined cyclopropenone-masked dibenzocyclooctyne functionalized polymers from atom transfer radical polymerization
-
Two functional atom transfer radical polymerization (ATRP) initiators (I-2 and I-3) were developed bearing a cyclopropenone-masked dibenzocyclooctyne group. ATRP was then explored on three main kinds of monomers for radical polymerization including acryla
- Sun, Peng,Yan, Guowei,Tang, Qingquan,Chen, Yongming,Zhang, Ke
-
p. 202 - 209
(2015/05/05)
-
- Synthesis of 2-bromo-1-aryl-1H-indenes via a Ag(I) promoted domino 2π-electrocyclic ring-opening/4π-electrocyclization reaction of 1,2-diaryl substituted gem-dibromocyclopropanes
-
2-Bromo-1-aryl substituted indenes can be synthesized from 1,2-diaryl substituted gem-dibromocyclopropanes via a domino reaction sequence. The cascade reaction involves silver(I) promoted ionization and 2π-disrotatory electrocyclic ring-opening, followed by a 4π-conrotatory electrocyclic ring closing reaction of the allylic carbocation intermediate. Reaction conditions utilize silver tetrafluoroborate (AgBF4) in dichloroethane at 65 C. Selectivity effects for the electrocyclization were also studied. The 2-bromoindenes can be further functionalized using cross-coupling reactions, such as the Suzuki-Miyaura protocol. The alkene π-bond of the indenes can also be isomerized to give the thermodynamically more stable 2-bromo-3-aryl-1H-indene isomers using triethylamine in dichloromethane at room temperature.
- Rosocha, Gregory,Batey, Robert A.
-
p. 8758 - 8768
(2013/09/23)
-
- Olefin cross-metathesis/Suzuki-Miyaura reactions on vinylphenylboronic acid pinacol esters
-
A series of alkenyl phenylboronic acid pinacol esters has been synthesized via an olefin cross-metathesis reaction of vinylphenylboronic acid pinacol ester derivatives. After catalytic hydrogenation, the resulting boronates were coupled via a microwave-mediated Suzuki-Miyaura reaction to afford a library of biarylethyl aryl and biarylethyl cycloalkyl derivatives. A complementary reaction sequence involved an initial Suzuki-Miyaura coupling.
- Baltus, Christine B.,Chuckowree, Irina S.,Press, Neil J.,Day, Iain J.,Coles, Simon J.,Tizzard, Graham J.,Spencer, John
-
supporting information
p. 1211 - 1217
(2013/03/13)
-
- Synthesis of combretastatin A-4 O-alkyl derivatives and evaluation of their cytotoxic, antiangiogenic and antitelomerase activity Dedicated to Professor G. Asensio, University of Valencia, on the occasion of his 65th birthday
-
We here report the synthesis and biological evaluation of several combretastatin A-4 derivatives alkylated at the phenol hydroxyl group. Some of these derivatives contain an (E)-arylalkene fragment reminiscent of that present in some natural stilbenes like resveratrol. The cytotoxicities towards one human healthy kidney embryonic and two tumoral cell lines were determined. In addition, the ability of these compounds to inhibit the production of the vascular endothelial growth factor (VEGF) was measured. Finally, the expression of genes controlling the production of telomerase was measured. Some of the compounds were found to have an activity comparable or higher than that of combretastatin A-4 in at least one of the aforementioned biological properties. The compounds with the (E)-arylalkene fragment were in general terms more active than the simple O-alkyl derivatives. However, no clear structure/activity correlations were perceived when comparing the observed compound activities across the three biological properties. This points out the existence of marked differences between the mechanisms responsible for their cytotoxicity.
- Torijano-Gutiérrez, Sandra,Díaz-Oltra, Santiago,Falomir, Eva,Murga, Juan,Carda, Miguel,Marco, J. Alberto
-
p. 7267 - 7274
(2013/11/19)
-
- Assisted tandem catalytic cross metathesis-oxidation: In one flask from styrenes to 1,2-diketones and further to quinoxalines
-
1,2-Diketones were synthesized from styrenes by combining a cross metathesis and a Ru-catalyzed alkene oxidation to an assisted tandem catalytic sequence. The synthesis relies on the use of just one metathesis precatalyst, which was in situ converted to the oxidation catalyst by addition of an alkyl hydroperoxide as a chemical trigger and oxidant. The one-flask sequence can be extended beyond 1,2-diketones to quinoxalines, by condensation of the oxidation products with ortho-phenylenediamine.
- Schmidt, Bernd,Krehl, Stefan,Hauke, Sylvia
-
p. 5427 - 5435
(2013/07/25)
-
- Polar dibenzocyclooctynes for selective labeling of extracellular glycoconjugates of living cells
-
Although strain-promoted alkyne-azide cycloadditions (SPAAC) have found wide utility in biological and material sciences, the low polarity and limited water solubility of commonly used cyclooctynes represent a serious shortcoming. To address this problem, an efficient synthetic route has been developed for highly polar sulfated dibenzocyclooctynylamides (S-DIBO) by a Friedel-Crafts alkylation of 1,2-bis(3-methoxyphenyl)ethylamides with trichlorocyclopropenium cation followed by a controlled hydrolysis of the resulting dichlorocyclopropenes to give bis(3-methoxyphenyl)cyclooctacyclopropenones, which were subjected to methoxy group removal of the phenols, O-sulfation, and photochemical unmasking of the cyclopropenone moiety. Accurate rate measurements of the reaction of benzyl azide with various dibenzylcyclooctyne derivatives demonstrated that aromatic substitution and the presence of the amide function had only a marginal impact on the rate constants. Biotinylated S-DIBO 8 was successfully used for labeling azido-containing glycoconjugates of living cells. Furthermore, it was found that the substitution pattern of the dibenzylcyclooctynes influences subcellular location, and in particular it has been shown that DIBO derivative 4 can enter cells, thereby labeling intra- and extracellular azido-modified glycoconjugates, whereas S-DIBO 8 cannot pass the cell membrane and therefore is ideally suited for selective labeling of cell surface molecules. The ability to selectively label cell surface molecules will yield unique opportunities for glycomic analysis and the study of glycoprotein trafficking.
- Friscourt, Frederic,Ledin, Petr A.,Mbua, Ngalle Eric,Flanagan-Steet, Heather R.,Wolfert, Margreet A.,Steet, Richard,Boons, Geert-Jan
-
supporting information; experimental part
p. 5381 - 5389
(2012/05/20)
-
- Convenient and stereoselective synthesis of symmetrical (E)-stilbenes via homocoupling of 1,3-dibenzylbenzotriazolium bromides
-
Using NaH as the base and DMSO as the solvent, a series of symmetric (E)-stilbenes were prepared in good yields via the -homocoupling of 1,3-dibenzylbenzotriazolium bromides at room temperature. Georg Thieme Verlag Stuttgart · New York.
- Xiao, Xiaohui,Lin, Daqin,Tong, Shuitian,Luo, Hong,He, Yinfeng,Mo, Hailan
-
supporting information; experimental part
p. 1731 - 1734
(2011/09/16)
-
- Palladium-catalyzed reduction of alkynes employing HSiEt3: stereoselective synthesis of trans- and cis-alkenes
-
The palladium-catalyzed semi-hydrogenation of alkynes to trans- or cis-alkenes employing HSiEt3 as the reductant is developed. The CuSO4 played a significant role for the trans/cis stereoselectivity. The labeling study revealed that the two olefinic hydrogen atoms came from HSiEt3 and H2O, respectively.
- Luo, Fang,Pan, Changduo,Wang, Wenhui,Ye, Zhishi,Cheng, Jiang
-
supporting information; experimental part
p. 1399 - 1403
(2010/04/04)
-
- Design of living ring-opening alkyne metathesis
-
It's alive: A ring-strained alkyne based on dibenzo[a,e][8]annulene undergoes ringopening metathesis polymerization (ROMP) to give a high-molecular-weight poly(ortho-phenylene) featuring alternating ethyl and ethynyl linkers along the polymer backbone. The molybdenumalkylidyne- based catalyst system discriminates between strained and unstrained alkynes to yield a living polymer with an unparalleled low polydispersity.
- Fischer, Felix R.,Nuckolls, Colin
-
supporting information; experimental part
p. 7257 - 7260
(2010/11/05)
-
- Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents
-
When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n- butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The EIZ ratio seems to depend on the amount of the base used and the phosphonium salt involved.
- Ngwendson, Julius N.,Schultze, Cassandra M.,Bollinger, Jordan W.,Banerjee, Anamitro
-
p. 668 - 675
(2008/09/21)
-
- Stereoselective synthesis of olefins by a reductive coupling reaction
-
Ketones and aldehydes are converted to symmetrical and (E)-olefins (1-15) by reaction with 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (PhPSe2)2, Woollins' reagent, in refluxing toluene; use of diketones was demonstrated by the reaction of PhC(O)CH2C(O)Ph which gives 1,2,4,5-tetraphenylbenzene (16) in 83% yield. The Royal Society of Chemistry 2007.
- Hua, Guoxiong,Li, Yang,Slawin, Alexandra M. Z.,Woollins, J. Derek
-
p. 1477 - 1480
(2007/10/03)
-
- Enantioselective ring-opening reaction of meso-epoxides with ArSH catalyzed by a C2-symmetric chiral bipyridyldiol-titanium complex
-
This study describes a C2-symmetric ligand comprising a central bipyridine-pinene-derived core and two functionalized diphenylmethanol subunits. [8′-(Hydroxy-diphenyl-methyl)-10,10,10′,10′-tetramethy l-[5,5′]bi[6-aza-tricyclo[7.1.1.02,7/s
- Chen, Yi-Jing,Chen, Chinpiao
-
p. 1313 - 1319
(2008/02/09)
-
- A simple access to biologically important trans-stilbenes via Ru-catalyzed cross metathesis
-
The cross metathesis of methoxy- or acetoxy-substituted styrenes using the Grubbs II catalyst affords unsymmetrical (mixed) E-stilbenes with astonishingly high selectivity (up to 79% yield). This approach offers a short and flexible synthesis of variously substituted stilbenes, which are derivatives or precursors of biologically important compounds such as resveratrol, piceatannol, and pinostilbene. Georg Thieme Verlag Stuttgart.
- Velder, Janna,Ritter, Stefanie,Lex, Johann,Schmalz, Hans-Guenther
-
p. 273 - 278
(2007/10/03)
-
- A convenient synthesis of symmetric 1,2-diarylethenes from arylmethyl phosphonium salts
-
Symmetric ethenyldithiophenes are important intermediates for synthesis of photochromic materials and organic conductors. When acetonitrile is used as a solvent, 3-methylthiophenylphosphonium salts form symmetric ethenyldithiophenes in the presence of a strong base (e.g., NaH, tBuOK) in moderate to high yields. This homocoupling reaction is faster than a Wittig reaction with aromatic ketones in acetonitrile. Our study shows that the presence of polar aprotic solvents promotes the homocoupling reaction.
- Ngwendson, Julius N.,Atemnkeng, Walters N.,Schultze, Cassandra M.,Banerjee, Anamitro
-
p. 4085 - 4088
(2007/10/03)
-
- Synthesis, X-ray structures and chemistry of enantiomerically pure 10,11-dihydro-5-phenyl-5H-dibenzo[b,f]phosphepine 5-oxides
-
Several phosphepine oxides were synthesised in optically pure form. Sharpless asymmetric dihydroxylation was used to introduce the chiral centres in all cases. Ring closure was achieved using either PhPCl2 or PrPCl2 together with a double nucleophile generated by either a double ortho-lithiation or double bromine-lithium exchange. The X-ray crystal structures of three phosphepine oxides illustrate their different conformations. The NMR spectra of several phosphepine oxides are described as is the chemistry which is shown to differ from that of acyclic phosphine oxides.
- Wyatt, Paul,Warren, Stuart,McPartlin, Mary,Woodroffe, Tom
-
p. 279 - 297
(2007/10/03)
-
- Synthesis of stilbenes via homocoupling of aryl aldehyde tosylhydrazones
-
Stilbenes are readily prepared in good yields via homocoupling of aryl aldehyde tosylhydrazones in the presence of lithium tert-butoxide and trimethyl borate under reflux in THF.
- Kabalka, George W,Wu, Zhongzhi,Ju, Yuhong
-
p. 4759 - 4760
(2007/10/03)
-
- Synthesis and photocyclization of macrocyclic stilbene derivatives
-
The stereoselectivity of the formation of macrocyclic stilbenes as well as the regioselectivity of their photocyclization are strongly influenced by the length of the connecting alkanediyl chain. The stereoisomers of the macrocyclic stilbenes and the corr
- Dyker, Gerald,K?rning, Jutta,Stirner, Wolfgang
-
p. 149 - 154
(2007/10/03)
-
- Substituent Effect Studies of Aryl-Assisted Solvolyses. I. The Acetolysis of 2,2-Bis(substituted phenyl)ethyl p-Toluenesulfonates
-
The substituent effect on the acetolysis of 2,2-bis(substituted phenyl)ethyl p-toluenesulfonates at 90.10 deg C can be described accurately in terms of the Yukawa-Tsuno (LArSR) relationship, giving a ρ value of -4.44 and an r value of 0.53. The substituent effect correlation of this system carrying two aryls is quite comparable to that of the 2-methyl-2-phenylpropyl system carrying a single aryl group, suggesting the close similarity in the structure of the transition states between the systems. The results can be reasonably accounted for on the basis of the accepted mechanism of this reaction, involving a rate-determining aryl-assisted transition state where only one aryl group of the two β-aryl groups participates.
- Fujio, Mizue,Maeda, Yasuyuki,Goto, Mutsuo,Saeki, Yoshihiro,Mishima, Masaaki,Tsuno, Yuho
-
p. 3015 - 3020
(2007/10/02)
-
- Synthesis and nematocidal activity of hydroxystilbenes
-
Various (E)-hydroxystilbenes were synthesized from (E)/(Z) mixtures of methoxystilbenes through a new (Z)-(E) isomerization method followed by demethylation. The nematocidal activity appears when methoxystilbenes are demethylated to hydroxystilbenes. For this activity, a hydroxy group at the C-2 or C-3 position is necessary. Thus, 2-hydroxy-, 3-hydroxy-, 2,6-dihydroxy-, 3,4-dihydroxy-, 3,5-dihydroxy-, 2,2'-dihydroxy-, 3,3'-dihydroxy-, 3,4'dihydroxy-, 2-hydroxy-4-methoxy-, 5-hydroxy-2-methoxy-, 2-hydroxy-6-methoxy-, 6-allyloxy-2-hydroxy-, 3-hydroxy-5-methoxy-, and 5-allyloxy-3-hydroxystilbenes showed rather potent nematocidal activity. The activity of 5-allyloxy-3-hydroxystilbene was the strongest [minimal lethal concentration (MLC) = 30 μM]. The activities of the (E) and (Z) isomers were comparable. The activities were also retained, though they were weaker, in the dihydro derivatives, hydroxybibenzyls.
- Ali,Kondo,Tsuda
-
p. 1130 - 1136
(2007/10/02)
-
- REDUCTIVE COUPLING OF BENZOIC ACID HALIDES AND ESTERS USING LOW-VALENT TITANIUM
-
The reductive coupling of (substituted) benzoic acid chlorides and esters is achieved using low-valent titanium, generated from TiCl3 and LiAlH4.Both acid chlorides and esters seem to follow the same two reaction pathways: one path via tolanes to stilbenes, the other via benzils to complex mixtures of products arising from reduction and further coupling reactions.Although the exact product balance depends upon the reaction conditions the major product is (substituted) cis-stilbene.
- Dang, Y.,Geise, H. J.
-
p. 375 - 380
(2007/10/02)
-
- Reductive Coupling of Geminal Dichlorides by Iron(II) Oxalate Dihydrate
-
A facile procedure for the quantitative conversion of geminal dichlorides to E olefins with iron(II) oxalate dihydrate in refluxing anhydrous dimethylformamide under a nitrogen atmosphere is described.The coupling proceeds via the corresponding vicinal dichlorides.
- Khurana, Jitender M.,Maikap, Golak C.,Mehta, Sanjay
-
p. 731 - 732
(2007/10/02)
-
- THE REACTIONS OF HYDRAZONES AND RELATED COMPOUNDS WITH STRONG BASES. PART 4. 4,5-DIARYL-1,2,3-TRIAZOLES FROM AROMATIC ALDEHYDE AZINES AND FROM THE REACTION OF ARENECARBONITRILES WITH ARYLDIAZOMETHANES
-
Reaction of aromatic aldehyde azines in dimethyl sulphoxide at 20 deg C with potassium t-butoxide gave 4,5-diaryl-1,2,3-triazoles (4) and stilbenes.Mechanisms were studied by addition of possible intermediates and by (14)C tracer methods.The synthesis of 4,5-diaryl-1,2,3-triazoles from arenecarbonitriles, aryldiazomethanes, and potassium t-butoxide in toluene is described and the mechanism is discussed.
- Grundon, Michael F.,Khan, Ejaz A.
-
p. 2917 - 2920
(2007/10/02)
-
- THE EFFECT OF ARYL SUBSTITUENTS ON ARYLCARBENE REACTIVITY
-
Substituted (p-MeO, p-Me, H, p-Cl, p-Br, m-Br, m-MeO, 3,4-Cl2, p-CO2Me, m-CN and p-CN) monophenylcarbenes are generated in a binary mixture of substrates (methanol, cis-4-methyl-2-pentene and cyclohexane) and the relative rate of O - H insertion into methanol to stereospecific cyclopropanation of the olefin to C - H insertion into cyclohexane are calculated from the ratios of products and substrates.It is found (i) that the reactivities of the substrates decrease in the order of methanol, olefin and cyclohexane and (ii) that electron-donating substituents generally lead to reaction with the more reactive substrates while the reaction with the less reactive substrates is favoured in the case of electron-withdrawing substituents.These results are interpreted in terms of the change in the electrophilicity of the singlet arylcarbene by the substituents rather than the change in the singlet-triplet equilibrium.
- Tomioka, Hideo,Tabayashi, Kazuo,Ozaki, Yasuji,Izawa, Yasuji
-
p. 1435 - 1440
(2007/10/02)
-
- Process for the preparation of styrene derivatives and/or stilbene derivatives
-
Compounds of the formulae in which Z represents unsubstituted or substituted phenyl or naphthyl, Z1 represents hydrogen or has the same meaning as Z and Z2 represents unsubstituted or substituted phenylene, naphthylene or p-biphenylene or an unsubstituted or substituted stilbene radical, can be obtained in a simple and economical manner in accordance with a novel process by reacting ethylene, under a pressure of 0.1 to 20 bar, in the presence of a base and with the addition of specific palladium catalysts, such as palladium acetate, with appropriate acid halides. The compounds of the formulae Ia and Ib are valuable intermediates, in particular for the preparation of fluorescent brighteners or scintillators.
- -
-
-
- SYNTHESIS OF STYRENE AND STILBENE DERIVATIVES BY THE PALLADIUM-CATALYSED ARYLATION OF ETHYLENE WITH AROYL CHLORIDES
-
The arylation of ethylene with aroyl chlorides, catalysed by palladium(II) acetate, leads to styrene and stilbene derivatives.By appropriate choice of reaction conditions, particularly the ethylene pressure, the reaction can be made to produce either styrene or stilbene derivatives selectively.The reaction tolerates those common substituents which do not react with aroyl chlorides.Only trans-stilbene derivatives are formed.
- Spencer, Alwyn
-
p. 117 - 122
(2007/10/02)
-