- Copper(0) nanoparticle catalyzed Z-Selective Transfer Semihydrogenation of Internal Alkynes
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The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromatic- substituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo- and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes. (Figure presented.).
- Moran, Maria Jesus,Martina, Katia,Bieliunas, Vidmantas,Baricco, Francesca,Tagliapietra, Silvia,Berlier, Gloria,De Borggraeve, Wim M.,Cravotto, Giancarlo
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p. 2850 - 2860
(2021/05/06)
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- Efficient photocatalytic chemoselective and stereoselective C-C bond formation over AuPd@N-rich carbon nitride
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Heterogeneous chemoselective or stereoselective C-C coupling reactions remain extremely challenging in traditional organic synthesis. Here, we constructed a AuPd@N-rich carbon nitride (NRCN) photocatalyst through simple ammonia solution heat treatment of carbon nitride and then AuPd NP loading. AuPd@NRCN exhibited extraordinary light color promoted catalytic performance in C-C bond formation under visible light in air. Surprisingly, both high chemoselectivity to unsymmetrical Ullmann biaryl products and satisfactory stereoselectivity to Z-type Heck reaction products could be achieved by changing the light source color. Various substrates exhibited great potential for the economical synthesis of unsymmetrical biaryl products and Z-type olefins. Efficient visible light promoted C-I bond activation accompanied with improved photocatalytic coupling reaction efficiency over AuPd@NRCN was verified firstly by in situ DRIFTS. Considering that the Ullmann cross-coupling reaction is a multi-photon reaction, the improved photocatalytic performance in the Ullmann cross-coupling reaction using a combination of light sources with different colors might be due to the activation of different substrates and/or steps requiring different energies, and the combination of the two energy sources was beneficial for improving the activation efficiency of different substrates and/or steps. The activation of iodobenzene and styrene in the Heck reaction with light was also beneficial to the formation of the stilbene product. The light color promoted chemoselectivity and stereoselectivity are expected to have profound impact on organic synthetic methodology improvement. This journal is
- Jiang, Heyan,Xu, Jie,Zhang, Sishi,Cheng, Hongmei,Zang, Cuicui,Bian, Fengxia
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p. 219 - 229
(2021/01/28)
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- E, Z -Selectivity in the reductive cross-coupling of two benzaldehydes to stilbenes under substrate control
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Unsymmetrical E- and Z-stilbenes can be synthesized from two differently substituted benzaldehydes in a MesP(TMS)Li-promoted reductive coupling sequence. Depending on the order of addition of the two coupling partners, the same olefin can be produced in either E- or Z-enriched form under identical reaction conditions. A systematic study of the correlation between the stereochemical outcome of the reaction and the substitution pattern at the two aldehydes is presented. The results can be used as guidelines to predict the product stereochemistry. This journal is
- Arkhypchuk, Anna I.,D'Imperio, Nicolas,Ott, Sascha
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p. 6171 - 6179
(2020/10/21)
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- Chemoselective Hydrogenation of Alkynes to (Z) -Alkenes Using an Air-Stable Base Metal Catalyst
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A highly selective hydrogenation of alkynes using an air-stable and readily available manganese catalyst has been achieved. The reaction proceeds under mild reaction conditions and tolerates various functional groups, resulting in (Z)-alkenes and allylic alcohols in high yields. Mechanistic experiments suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperativity.
- Zubar, Viktoriia,Sklyaruk, Jan,Brzozowska, Aleksandra,Rueping, Magnus
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supporting information
p. 5423 - 5428
(2020/07/24)
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- Stereoselective Chromium-Catalyzed Semi-Hydrogenation of Alkynes
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Chromium complexes have found very little applications as hydrogenation catalysts. Here, we report a Cr-catalyzed semi-hydrogenation of internal alkynes to the corresponding Z-alkenes with good stereocontrol (up to 99/1 for dialkyl alkynes). The catalyst comprises the commercial reagents chromium(III) acetylacetonate, Cr(acac)3, and diisobutylaluminium hydride, DIBAL?H, in THF. The semi-hydrogenation operates at mild conditions (1-5 bar H2, 30 °C).
- Gregori, Bernhard J.,Nowakowski, Michal,Schoch, Anke,P?llath, Simon,Zweck, Josef,Bauer, Matthias,Jacobi von Wangelin, Axel
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p. 5359 - 5363
(2020/09/03)
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- Methanol as the Hydrogen Source in the Selective Transfer Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex
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The first base metal-catalyzed transfer hydrogenation of alkynes with methanol is described. An air and moisture stable manganese pincer complex catalyzes the reduction of a variety of different alkynes to the corresponding (Z)-olefins in high yields. The
- Sklyaruk, Jan,Zubar, Viktoriia,Borghs, Jannik C.,Rueping, Magnus
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supporting information
p. 6067 - 6071
(2020/08/28)
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- Ligand-controlled iridium-catalyzed semihydrogenation of alkynes with ethanol: highly stereoselective synthesis of E- and Z-alkenes
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A ligand-controlled iridium-catalyzed semihydrogenation of alkynes to E- and Z-alkenes with ethanol was developed. Effective selectivity control was achieved by ligand regulation. The use of 1,2-bis(diphenylphosphino)ethane (DPPE) and 1,5-cyclooctadiene (COD) was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 40 alkenes, with good stereoselectivities. The value of our approach in practical applications was investigated by studying the effects of pinosylvin and 4,4′-dihydroxystilbene (DHS) on zebrafish as a vertebrate model.
- Yang., Jinfei,Wang, Chengniu,Sun, Yufeng,Man, Xuyan,Li, Jinxia,Sun, Fei
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supporting information
p. 1903 - 1906
(2019/05/02)
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- Carbonyl–Olefin Cross-Metathesis Through a Visible-Light-Induced 1,3-Diol Formation and Fragmentation Sequence
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A visible-light-mediated approach to carbonyl–olefin cross-metathesis is described. Photoinduced hole catalysis was used to promote the formation of 1,3-diols from aldehydes and styrenes, which were then readily fragmented under acidic conditions to form the cross-metathesis products. The use of 1,3-diols as intermediates, rather than the energetically more demanding oxetanes, provides a new, orthogonal mechanistic strategy for carbonyl–olefin cross-metathesis. Furthermore, this approach does not require any metals, ligands, or additives, and provides the products with high levels of E selectivity. A mechanistic rationale is provided and supported by both theoretical calculations and experiments. Additionally, a practical synthesis of a new acridinium-based photocatalyst, including full characterization, is presented.
- Pitzer, Lena,Sandfort, Frederik,Strieth-Kalthoff, Felix,Glorius, Frank
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p. 16219 - 16223
(2018/11/23)
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- Active Ruthenium (0) Nanoparticles Catalyzed Wittig-Type Olefination Reaction
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Abstract: Five different Ru metal precursors were reduced in imidazolium based ionic liquids under hydrogen atmosphere (4?bar) at 50 °C to obtain well-dispersed and stable Ru nanoparticles. Transmission electron microscopy (TEM) analysis confirmed size of well dispersed ionic liquid mediated Ru particles (Ru NPs) of 5?nm (±0.5) in diameter. These ruthenium nanoparticles (in ionic liquids) were used for Wittig type olefination reaction under mild reaction environment (70 °C and 1?h). The corresponding stilbenes were obtained in good yield with low-average selectivity. The proposed methodology is especially efficient for the synthesis of stilbenes as they were synthesized in the absence of any additive (as a hydrogen acceptor). The new catalytic system was also successfully applied for the synthesis of polymethoxylated and polyhydroxylated stilbenes, including resveratrol and DMU-212. Graphical Abstract: [Figure not available: see fulltext.]
- Srivastava, Vivek
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p. 693 - 703
(2017/03/08)
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- Z-Stereoselective Aza-Peterson Olefinations with Bis(trimethylsilane) Reagents and Sulfinyl Imines
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Highly stereoselective aza-Peterson olefinations from bench-stable α,α-bis(trimethylsilyl)toluene reagents and N-substituted imines have been achieved using TMSO-/Bu4N+ as Lewis base activator in THF. Remarkably, and for the first time, N-t-butanesulfinyl imines were utilized for the synthesis of Z-stilbenes with excellent selectivities, while N-aryl imines generated E-stilbenes under identical reaction conditions. The protocol proved general for numerous examples with low molecular weight byproducts formed. The origin of the Z-selectivity is proposed to be a result of diastereoselective addition to N-t-butanesulfinyl imines followed by syn-elimination of an in situ formed hypervalent silicate.
- Das, Manas,OShea, Donal F.
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supporting information
p. 336 - 339
(2016/02/03)
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- Nickel-Catalyzed Boron Insertion into the C2-O Bond of Benzofurans
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Treatment of benzofurans with bis(pinacolato)diboron and Cs2CO3 under nickel-NHC catalysis resulted in the insertion of a boron atom into the C2-O bond of benzofurans to afford the corresponding oxaborins. The scope of benzofuran substrates is wide, and the reactions proceeded without loss of functional groups such as fluoro, methoxy, and ester that are potentially reactive under nickel catalysis. The boron-inserted products proved to be useful building blocks and subsequently underwent a series of transformations, one of which led to the synthesis of fluorescent π-expanded oxaborins.
- Saito, Hayate,Otsuka, Shinya,Nogi, Keisuke,Yorimitsu, Hideki
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p. 15315 - 15318
(2016/12/09)
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- Iridium-Catalyzed Intramolecular Methoxy C?H Addition to Carbon–Carbon Triple Bonds: Direct Synthesis of 3-Substituted Benzofurans from o-Methoxyphenylalkynes
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Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C?H bond of a methoxy group in 1-methoxy-2-(arylethynyl)benzenes across a carbon–carbon triple bond took place efficiently either in toluene at 110 °C or in p-xylene at 135 °C in the presence of an iridium catalyst. The initial 5-exo cyclization products underwent double-bond migration during the reaction to give 3-(arylmethyl)benzofurans in high yields.
- Torigoe, Takeru,Ohmura, Toshimichi,Suginome, Michinori
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p. 10415 - 10419
(2016/07/21)
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- Regioselectivity observed in manganese(III) acetate mediated addition of acetylacetone to various alkenes: mechanistic and theoretical studies
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Various alkenes substituted at the 1,2-positions by 2-thiophenyl, 3-thiophenyl, and phenyl substituted by electron-withdrawing and electron-donating groups were treated with acetylacetone in the presence of Mn(OAc)3in acetic acid. In cases wher
- Ceyhan, Selin,Cetinkaya, Yasin,Akdag, Akin,Balci, Metin
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supporting information
p. 6815 - 6824
(2016/10/04)
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- Synthesis of 2-phenylnaphthalenes from styryl-2-methoxybenzenes
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A new simple and efficient method for the synthesis of 2-phenylnaphthalenes from electron-rich 1-styryl-2-methoxybenzenes has been described. The reaction proceeds via TFA catalyzed C-C bond cleavage followed by intermolecular [4+2]-Diels-Alder cycloaddition of an in situ formed styrenyl trifluoroacetate intermediate. The quantum chemical calculations identified the transition state for the cycloaddition reaction and helped in tracing the reaction mechanism. The method has been efficiently utilized for synthesis of the phenanthrene skeleton and a naphthalene-based potent and selective ER-β agonist. This journal is
- Mudududdla, Ramesh,Sharma, Rohit,Abbat, Sheenu,Bharatam, Prasad V.,Vishwakarma, Ram A.,Bharate, Sandip B.
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supporting information
p. 12076 - 12079
(2015/02/19)
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- How the substitution faraway from NHCs affects the structural features and catalytic activity of dicarbene dipalladium complexes
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A series of [PdPyCl2]2(di-NHC) complexes were prepared (di-NHC are two 1-(2,6-dimethylphenyl)imidazolidene molecules bridged by an aliphatic -(CH2)n- linker (n = 3, 4, 5, 6, and 10)). All complexes were fully characterized by NMR spectroscopy and elemental analyses. The crystal structures of four complexes (n = 3, 4, 5 and 6) were determined by X-ray diffraction. The influence of the distant methyl group on the structural features and catalytic activity with increasing of length of linker was investigated by comparing the results of these 2,6-dimethylphenyl palladium complexes with those of their known mesityl analogues. X-ray studies show the distant methyl substitution has big impact on the structure feature of the complexes with the shorter linker between two NHC (ethylene and propylene), but has a little or no effect on that of the complexes with longer linker (butylene and hexylene). Catalytic results of the arylation of styrene show that the remote substitute has big effect on the regioselectivity of the product in all complexes with shorter and longer linkers, but has a limited effect on the yield. Copyright
- Ge, Kaiqi,Cao, Changsheng,Liu, Gang,Li, Yuling,Zhang, Juan,Pang, Guangsheng,Shi, Yanhui
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p. 444 - 450
(2014/03/21)
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- Palladium complexes with picolyl functionalized N-heterocyclic carbene ligands and their application in the Mizoroki-Heck reaction
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A series of Pd complexes of picoline-functionalized N-heterocyclic carbenes with different substituents were synthesized. The molecular structures of selected complexes were determined by X-ray diffraction studies, showing a pseudo-square-planar structure with a Pd center surrounded by carbene, pyridine, and two chloride ligands. The influence of the different substituents on the structure and reactivity of the complexes has been studied. The catalytic properties of the complexes were investigated in the Mizoroki-Heck reaction for cross-coupling of bromobenzene with a variety of aryl halides. Their performances varied in these reactions but showed good product regioselectivities.
- Cao, Changsheng,Sun, Rui,Chen, Qian,Lv, Lanlan,Shi, Yanhui,Pang, Guangsheng
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p. 351 - 358
(2013/07/05)
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- Unequivocal experimental evidence for a unified lithium salt-free wittig reaction mechanism for all phosphonium ylide types: Reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products
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The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
- Byrne, Peter A.,Gilheany, Declan G.
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supporting information; experimental part
p. 9225 - 9239
(2012/07/14)
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- Synthesis, structure and catalytic activity of dicarbene dipalladium complexes with different substituents
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A series of ethylene bridged di-NHC dipalladium complexes (1-5) with different substituents on N of imidazolydene were prepared. The influence of the different substituents on the structure and catalytic reactivity of the complexes were studied. The molecular structures of 3 and 4 were determined by X-ray diffraction studies. The structures of complexes consist of two perpendicular pseudo-square-planar subunits in a cis configuration. The catalytic activity of the new binuclear palladium complexes was successfully tested in the Mizoroki-Heck reaction. The complexes with aryl substituent have better activity than that with alkyl substituent, meanwhile, the different substituents on phenyl group have a little effect on both regioselectivity and the yield of the product as well.
- Yang, Long,Zhao, Jianfeng,Li, Yunfei,Ge, Kaiqi,Zhuang, Yongzhong,Cao, Changsheng,Shi, Yanhui
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experimental part
p. 33 - 36
(2012/08/14)
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- A convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions
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A mild method for the facile removal of phosphine oxide from the crude products of Wittig and Appel reactions is described. Work-up with oxalyl chloride to generate insoluble chlorophosphonium salt (CPS) yields phosphorus-free products for a wide variety of these reactions. The CPS product can be further converted into phosphine.
- Byrne, Peter A.,Rajendran, Kamalraj V.,Muldoon, Jimmy,Gilheany, Declan G.
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p. 3531 - 3537
(2012/05/20)
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- Highly chemo- and stereoselective palladium-catalyzed transfer semihydrogenation of internal alkynes affording cis -alkenes
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DMF (N,N-dimethylformamide)/KOH was found to be an efficient hydrogen source in the Pd(OAc)2-catalyzed transfer semihydrogenation of various functionalized internal alkynes to afford cis-alkenes in good to high yields with excellent chemo- and stereoselectivity. This catalytic process was also applied to the synthesis of analogues of combretastatin A-4.
- Li, Jie,Hua, Ruimao,Liu, Tao
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supporting information; experimental part
p. 2966 - 2970
(2010/06/19)
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- Wittig-type olefination of alcohols promoted by nickel nanoparticles: Synthesis of polymethoxylated and polyhydroxylated stilbenes
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Nickel nanoparticles were found to promote the Wittig-type olefination of primary alcohols with phosphorus ylides. The latter can be prepared from the corresponding phosphonium salts with TiBuLi or in situ generated with lithium metal. The methodology is especially efficient for the synthesis of stilbenes and is applied in the absence of any additive as a hydrogen acceptor. A new approach, to the synthesis of polymethoxylated and polyhydroxylated stilbenes, including resveratrol, DMU-212 and analogues, is presented.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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supporting information; experimental part
p. 6034 - 6042
(2010/02/28)
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- One-pot synthesis of stilbenes from alcohols through a wittig-type olefination reaction promoted by nickel nanoparticles
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A series of stilbenes has been synthesised in one pot from benzyl alcohols and benzylidenetriphenylphosphorane through a Wittig-type olefination reaction in the presence of nickel nanoparticles. Georg Thieme Verlag Stuttgart.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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experimental part
p. 1579 - 1582
(2009/11/30)
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- Synthesis of stilbenes promoted by the mixture of zinc and iron powder
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Stilbenes have been synthesised by a one-pot reaction of aldehydes with benzyl bromide. The reaction was promoted by both triphenylphosphine and the mixture of zinc and iron together in sealed tube. The yields ranged from moderate to excellent.
- Zhanga, Zhiying,Xieb, Yuanyuan,Yua, Xiaochun
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experimental part
p. 140 - 142
(2009/10/15)
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- Manganese-catalyzed cross-coupling reaction between aryl grignard reagents and alkenyl halides
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(Chemical Equation Presented) Aryl Grignard reagents react stereospecifically with alkenyl halides in the presence of manganese chloride (10%) to afford good yields of cross-coupling products.
- Cahiez, Gerard,Gager, Olivier,Lecomte, Fabien
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supporting information; experimental part
p. 5255 - 5256
(2009/05/30)
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- One-pot hydrosilylation-protodesilylation of functionalized diarylalkynes: a highly selective access to Z-stilbenes. Application to the synthesis of combretastatin A-4
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An efficient stereoselective synthesis of Z-stilbenes has been developed from diarylalkynes via a new hydrosilylation-protodesilylation process. The scope and limitation of this method is presented to stereoselectively prepare a wide range of (Z)-stilbenes in a one-pot way is presented. A concise application to the preparation of combretastatin A-4 (CA-4), a vascular targeting agent inhibitor of tubulin polymerisation is described.
- Giraud, Anne,Provot, Olivier,Hamzé, Abdallah,Brion, Jean-Daniel,Alami, Mouad
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p. 1107 - 1110
(2008/09/17)
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- Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 12. Extrusion of Ph3P from sulfonyl ylides and reactivity of the resulting sulfonyl carbenes
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Twelve sulfonyl stabilised phosphorus ylides have been prepared and their behaviour upon flash vacuum pyrolysis at 600°C has been examined. Examples with an arylsulfonyl substituent undergo loss of Ph3PO to give intractable products but those with an arylmethylsulfonyl substituent separately lose Ph3P and SO2 to give products consistent with the intermediacy of sulfonyl carbenes. X-Ray structure determinations of one ylide from each series show a more significant P-O non-bonding interaction in the first case, providing some explanation for the different thermal reactivity.
- Aitken, R. Alan,Drysdale, Martin J.,Ferguson, George,Lough, Alan J.
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p. 875 - 880
(2007/10/03)
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- Development of a polymer bound Wittig reaction and use in multi-step organic synthesis for the overall conversion of alcohols to β-hydroxyamines
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An efficient combinatorial access to β-hydroxyamines suitable for automation is achieved by the mild oxidation of alcohols to aldehydes by polymer supported perruthenate (PSP), the subsequent clean olefination of the obtained aldehydes by polymer supported Wittig reagents followed by the epoxidation of the olefins by dimethyldioxirane (DMDO), and the final aminolysis of the epoxides with various amines is described.
- Bolli, Martin H.,Ley, Steven V.
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p. 2243 - 2246
(2007/10/03)
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- STEREOSELECTIVITY OF THE WITTIG-HORNER REACTION WITH BENZYLPHOSPHONATE CARBANIONS AND ALDEHYDES
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The interaction of Li-diethylbenzylphosphonate 1-Li with aldehydes 2 is studied at different reaction conditions, the corresponding β-hydroxyethanephosphonate 3 being isolated.It is found that in these cases the aldol stage of the HWE reaction is not stereoselective or threo isomers predominate.The elimination stage leads only to trans-alkene due to the electron and steric influence of the substituents at the phosphorus atom. Key words: Stereoselectivity; benzylphosphonate carbanion; reaction with aldehydes; threo/erythro ratio; 2-hydroxyphosphonates.
- Petrova, Jordanka,Momchilova, Snejana,Vassilev, Nikolay G.
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- OLEFIN FORMATION VIA N,N,N',N'-TETRAMETHYLDIAMIDES OF 1,2-DIARYL-2-HYDROXYETHANEPHOSPHONIC ACIDS IN ACIDIC MEDIA
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The olefin formation via the erythro-N,N,N',N'-tetramethyldiamides of 1,2-diaryl-2-hydroxyethanephosphonic acids 3,4 in the presence of aqueous hydrochloric acid proceeds not stereospecifically, while in ethanolic solution of hydrochloric acid (Z)-stereospecific olefin formation predominantly takes place.The mechanism of the elimination process is discussed.
- Petrova, Jordanka,Kirilov, Marko,Momchilova, Snejana,Kossev, Krassimir
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-
- OLEFIN SYNTHESIS VIA THE LITHIUM DERIVATIVES OF THE N,N,N',N'-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS. 2. SYNTHESIS OF SOME (Z)-ORTHO AND PARA SUBSTITUTED STILBENES
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The reaction of the lithium derivatives of N,N,N',N'-tetramethyldiamides of arylmethanophosphonic acids (1-Li) with ortho- and para-substituted benzaldehydes 2 is studied.Reaction conditions are found for erythro-stereoselective addition of 1 to 2 with high diastereomeric purity (95-99percent) of the rythro adducts 3, 4 (yields 35-72percent).By thermolysis of the adducts in neutral medium the corresponding (Z)-ortho and para-substituted silbenes 5, 6 are obtained.Some factors causing the predominant formation of the erythro adducts 3, 4, as well as the influence of the ortho-substituents on the equilibrium are discussed.
- Petrova, Jordanka,Momchilova, Snejana,Kirilov, Marko
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p. 243 - 250
(2007/10/02)
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