- CATALYTIC PHOSPHORYLATION OF POLYFLUOROALKANOLS. 13. SOME AMMONIUM AND PHOSPHONIUM SALTS AS PHOSPHYRYLATION CATALYSTS
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It was shown that it is possible to use a series of ammonium and phosphonium salts as effective catalysts for the preparative synthesis of tris(polyfluoroalkyl)phosphates.The effect of the structure of substituted ammonium salts on their catalytic activity was studied in the phosphorylation of 1,1-dihydroperfluorobutanol by phosphorus oxychloride.It was determined that the reaction rate is effected not only by the solubility of the salt, but also by the nature of the ion pair and the steric access of the onium center for solvation by phosphoryl compounds.
- Kabachnik, M. I.,Zakharov, L. S.,Kudryatsev, I. Yu.
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- Synthesis and coordination chemistry of pentadienyl ligands derived from (1 R)-(-)-myrtenal
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With the natural product (1R)-(-)-myrtenal as the starting material, a series of chiral pentadienes (Pdl*as dimethylnopadiene (2a), methylphenylnopadiene (2b), and methylnopadiene (2c) have been prepared by Wittig reactions. Deprotonation with the Schlosser base gives the corresponding potassium pentadienides 3a-K-3c-K, whose structures were investigated by NMR spectroscopy and X-ray diffraction studies. In all cases a "U" conformation was observed. Furthermore, the coordination chemistry and electronic properties of these new pentadienyl systems were explored in several half-open trozircene complexes [(η7-C7H 7)Zr(η5-Pdl)] and their PMe3 and tBuNC adducts. Density functional theory (DFT) computations are consistent with the experimentally observed face selectivity upon metal coordination: namely, that the metal coordinates exclusively from the sterically less encumbered side.
- Fecker, Ann Christin,Craciun, Bogdan-Florin,Freytag, Matthias,Jones, Peter G.,Walter, Marc D.
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- Nucleophilic 1,1-Difluoroethylation with Fluorinated Phosphonium Salt
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The fluorinated phosphonium salt (Ph3P+CF2CH3 BF4-) was shown to act as a nucleophilic 1,1-difluoroethylation agent to enable difluoroethylation of aldehydes and imines.
- Deng, Zuyong,Liu, Can,Zeng, Xian-Liang,Lin, Jin-Hong,Xiao, Ji-Chang
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- β-Amyrin Biosynthesis: The Methyl-30 Group of (3S)-2,3-Oxidosqualene Is More Critical to Its Correct Folding to Generate the Pentacyclic Scaffold than the Methyl-24 Group
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Oxidosqualene cyclases catalyze the transformation of oxidosqualene (1) into numerous cyclic triterpenes. Enzymatic reactions of 24-noroxidosqualene (8) and 30-noroxidosqualene (9) with Euphorbia tirucalli β-amyrin synthase were conducted to examine the role of the branched methyl groups of compound 1 in the β-amyrin biosynthesis. Substrate 8 almost exclusively afforded 30-nor-β-amyrin (>95.5%), which was produced through a normal cyclization pathway, along with minor products (4.5%). However, a lack of the Me-30 group (analogue 9) resulted in significantly high production of premature cyclization products, including 6/6/6/5-fused tetracyclic and 6/6/6/6/5-fused pentacyclic skeletons (64.6%). In addition, the fully cyclized product (35.4%) having the 6/6/6/6/6-fused pentacycle was produced; however, the normally cyclized product, 29-nor-β-amyrin was present in only 18.6% of these products. The conversion yield of substrate 8 possessing a Z-Me group at the terminus was approximately twofold greater than that of compound 9 with an E-Me group. Thus, the Me-30 group is essential for the correct folding of a chair-chair-chair-boat-boat conformation of compound 1 for the production of the β-amyrin scaffold, whereas the Me-24 group exerts little influence on the normal polycyclization cascade. Here, we show that the Me-30 group plays critical roles in constructing the ordered architecture of a chair-chair-chair-boat-boat structure, in facilitating the ring-expansion reactions, and in performing the final deprotonation reaction at the correct position.
- Hoshino, Tsutomu,Miyahara, Yuri,Hanaoka, Masaki,Takahashi, Kazunari,Kaneko, Ikki
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- Conformational Control of Initiation Rate in Hoveyda-Grubbs Precatalysts
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When the coordinating isopropyl ether of the Hoveyda precatalyst is replaced by a cyclohexyl ether, it is possible to control the substituent's conformation in either the equatorial or axial position. A stereodivergent synthesis of axial and equatorial cyclohexyl vinyl ethers provided access to new ruthenium metathesis precatalysts by carbene exchange. The conformational disposition of the coordinating aryl ether was found to have a significant effect on the reactivity of the precatalyst in alkene metathesis. The synthesis of four new Ru carbene complexes is reported, featuring either the 1,3-bis(2,4,6-trimethylphenyl)dihydroimidazolylidene (H2IMes) or the 1,3-bis(2,6-diisopropylphenyl)dihydroimidazolylidene (SIPr) N-heterocyclic carbene ligand. The conformational isomers in the SIPr series were structurally characterized. Performance testing of all new precatalysts in three different ring-closing metatheses and an alkene cross metathesis illustrated superior performance by the precatalysts bearing axial coordinating ethers. Initiation rates with butyl vinyl ether were also measured, providing a useful comparison to existing Hoveyda-type metathesis precatalysts. Use of conformational control of the coordinating ether substituent provides a new way to modulate reactivity in this important class of alkene metathesis precatalysts.
- Gregg, Zackary R.,Griffiths, Justin R.,Diver, Steven T.
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- Substituted dienes prepared from betulinic acid – Synthesis, cytotoxicity, mechanism of action, and pharmacological parameters
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A set of new substituted dienes were synthesized from betulinic acid by its oxidation to 30-oxobetulinic acid followed by the Wittig reaction. Cytotoxicity of all compounds was tested in vitro in eight cancer cell lines and two noncancer fibroblasts. Almost all dienes were more cytotoxic than betulinic acid. Compounds 4.22, 4.30, 4.33, 4.39 had IC50 below 5 μmol/L; 4.22 and 4.39 were selected for studies of the mechanism of action. Cell cycle analysis revealed an increase in the number of apoptotic cells at 5 × IC50 concentration, where activation of irreversible changes leading to cell death can be expected. Both 4.22 and 4.39 led to the accumulation of cells in the G0/G1 phase with partial inhibition of DNA/RNA synthesis at 1 × IC50 and almost complete inhibition at 5 × IC50. Interestingly, compound 4.39 at 5 × IC50 caused the accumulation of cells in the S phase. Higher concentrations of tested drugs probably inhibit more off-targets than lower concentrations. Mechanisms disrupting cellular metabolism can induce the accumulation of cells in the S phase. Both compounds 4.22 and 4.39 trigger selective apoptosis in cancer cells via intrinsic pathway, which we have demonstrated by changes in the expression of the crucial apoptosis-related protein. Pharmacological parameters of derivative 4.22 were superior to 4.39, therefore 4.22 was the finally selected candidate for the development of anticancer drug.
- Frydrych, Ivo,Urban, Milan,?arek, Jan,Benická, Sandra,D?ubák, Petr,Gurská, Soňa,Hajdúch, Marián,Kotulová, Jana,Li?ková, Barbora,Olejníková, Denisa,Pokorny, Jan
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- Organic phosphine salt and optical physical property regulation and control method and application thereof (by machine translation)
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The invention discloses an organic phosphine salt and an optical physical property regulation and control method and application, of the compound, with different alkyl chain lengths through an ion exchange reaction; to obtain the organic phosphine salt, with different alkyl chain lengths through the ion exchange reaction to control the photophysical property (Cl, Br, I), of the compound by using alkyl, chain length and heavy atom, after, ultraviolet irradiation to achieve information, encryption application 300 nm. (by machine translation)
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Paragraph 0045-0055
(2020/05/30)
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- Progress toward a Convergent, Asymmetric Synthesis of Jervine
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Progress toward a convergent approach for the enantioselective synthesis of the Veratrum alkaloid jervine is presented. The two requisite fragments were stereoselectively and efficiently fashioned from economical and readily available reagents. Key reactions include (a) a highly diastereoselective Ireland-Claisen rearrangement to establish the necessary cis-relationship between the amine and methyl group on the tetrahydrofuran E-ring; (b) a diastereoselective selenoetherification reaction that enabled the assembly of the D/E oxaspiro[4.5]decene in the needed configuration; and (c) an enzymatic desymmetrization of an abundant achiral diol en route to a key four-carbon building block as a practical alternative to a protected Roche ester reduction.
- De Jesús Cruz, Pedro,Johnson, Jeffrey S.,Zavesky, Blane P.
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supporting information
(2020/04/30)
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- Isoxazoline derivative and application thereof in agriculture
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The invention provides an isoxazoline derivative and application of the isoxazoline derivative in agriculture. Specifically, the invention provides a compound as shown in a formula (I) or a stereoisomer, nitrogen oxide or salt of the compound as shown in the formula (I), and a preparation method thereof. In the formula (I), R1, R2, R3, R4, n, R5, R6, R7, R8 and Acy are as defined in the invention.Further, the invention provides compositions containing these compounds and use thereof in agriculture, particularly as herbicidal active ingredients for controlling unwanted plants.
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Paragraph 0233; 0237-0238
(2020/11/25)
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- Visible Light Induced Cyclization to Spirobi[indene] Skeletons from Functionalized Alkylidienecyclopropanes
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In this paper, we revealed a metal-free and visible light photoinduced method for the rapid construction of spirobi[indene] skeletons, providing a simple and efficient way for easy access to spirobi[indene] scaffolds under mild conditions along with a broad substrate scope and good functional group tolerance.
- Li, Quanzhe,Liu, Jiaxin,Shi, Min,Wei, Yin
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supporting information
(2020/03/26)
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- Ionic liquid functionalized acid orange for organic solvent and preparation method thereof
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The invention relates to ionic liquid functionalized acid orange for an organic solvent and a preparation method thereof. The preparation method for the ionic liquid functionalized acid orange for theorganic solvent provided by the invention comprises the following steps: first, first, reacting triphenylphosphine and slightly excessive bromoalkane, and washing and purifying by using ethyl acetateto prepare alkyl triphenyl bromide; performing neutral reaction on acidified acid orange and silver carbonate, and washing and drying to prepare acid orange silver salt; then, respectively performingion exchange on the prepared acid orange silver salt and different alkyl triphenyl bromide to prepare a series of novel ionic liquid functionalized acid orange which can be dissolved in a plurality of organic solvents. The synthesis reaction conditions are mild and the post-treatment is simple. The type of ionic liquid functionalized acid orange has good solubility in the plurality of the organicsolvents, and is an azo dye and an acid base indicator which can be used for the organic solvent.
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Paragraph 0031-0034
(2019/08/20)
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- Exploring London Dispersion and Solvent Interactions at Alkyl–Alkyl Interfaces Using Azobenzene Switches
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Interactions on the molecular level control structure as well as function. Especially interfaces between innocent alkyl groups are hardly studied although they are of great importance in larger systems. Herein, London dispersion in conjunction with solvent interactions between linear alkyl chains was examined with an azobenzene-based experimental setup. Alkyl chains in all meta positions of the azobenzene core were systematically elongated, and the change in rate for the thermally induced Z→E isomerization in n-decane was determined. The stability of the Z-isomer increased with longer chains and reached a maximum for n-butyl groups. Further elongation led to faster isomerization. The origin of the intramolecular interactions was elaborated by various techniques, including 1H NOESY NMR spectroscopy. The results indicate that there are additional long-range interactions between n-alkyl chains with the opposite phenyl core in the Z-state. These interactions are most likely dominated by attractive London dispersion. This work provides rare insight into the stabilizing contributions of highly flexible groups in an intra- as well as an intermolecular setting.
- Strauss, Marcel A.,Wegner, Hermann A.
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supporting information
p. 18552 - 18556
(2019/11/19)
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- Aminoxyl-Catalyzed Electrochemical Diazidation of Alkenes Mediated by a Metastable Charge-Transfer Complex
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We report the development of a new aminoxyl radical catalyst, CHAMPO, for the electrochemical diazidation of alkenes. Mediated by an anodically generated charge-transfer complex in the form of CHAMPO-N3, radical diazidation was achieved across a broad scope of alkenes without the need for a transition metal catalyst or a chemical oxidant. Mechanistic data support a dual catalytic role for the aminoxyl serving as both a single-electron oxidant and a radical group transfer agent.
- Siu, Juno C.,Parry, Joseph B.,Lin, Song
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supporting information
p. 2825 - 2831
(2019/02/14)
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- Luminous ion type tetra-coordinated manganese compound as well as preparation method and application thereof
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The invention discloses preparation and application of a luminous ion type tetra-coordinated manganese compound. Aiming at solving various energy source and pollution problems caused by the fact thatprinting paper is used for one-time reading in the prior art, the invention provides the luminous ion type tetra-coordinated manganese compound; the compound can be used for the field of pure water copying printing paper and provides powerful supports for green printing in the future; synthesis steps of an organic phosphorus ligand provided by the invention are simple and conditions are moderate;the obtained ion type tetra-coordinated manganese compound has the advantages of low cost, easiness for obtaining and stable performance.
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Paragraph 0034; 0039
(2018/07/28)
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- A method of synthesis for fuwei intermediates (by machine translation)
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The invention discloses a method for synthesizing for fuwei intermediate of the method, the method comprises: formula 2 compound of formula 9 - propenyl adenine as raw materials, in the (S)- (-) - 2, 2 '- double (b benzene phosphine base) - 1, 1' - binaphthyl induction, and tetramethyl piperidine nitrogen oxide oxidation reaction to obtain the type 1 indicated by the tenofovir intermediate (R)- 9 - (2 - hydroxy-propyl) adenine; Through the method of the invention for the preparation of tenofovir intermediate (R)- 9 - (2 - hydroxy-propyl) adenine, mild reaction conditions, the industrial application and popularization; yield of the object product, good selectivity; without using a large amount of chiral compounds, the use of a small amount of chiral auxiliary can be induced oxidation, the cost is low. (by machine translation)
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Paragraph 0024; 0025
(2017/08/28)
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- Unique Triphenylphosphonium Derivatives for Enhanced Mitochondrial Uptake and Photodynamic Therapy
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In this study, unique methyl-functionalized derivatives (T?PP+) of the drug carrier triphenylphosphonium (TPP+) that exhibit significant enhancement of the accumulation of both the cation and its conjugated cargo in cell mitochondria are designed. We show that the presence of methyl group(s) at key positions within the phenyl ring results in an increase in the hydrophobicity and solvent accessible surface area of T?PP+. In particular, when the para position of the phenyl ring in T?PP+ is functionalized with a methyl group, the cation is most exposed to the surrounding environment, leading to a large decrease in water entropy and an increase in the level of van der Waals interaction with and partition into a nonpolar solvent. Therefore, stronger binding between the hydrophobic T?PP+ and mitochondrial membrane occurs. This is exemplified in a (hexachloro-fluorescein)-TPP+ conjugate system, where an ～12 times increase in the rate of mitochondrial uptake and a 2 times increase in photodynamic therapy (PDT) efficacy against HeLa and FU97 cancer cells are achieved when TPP+ is replaced with T?PP+. Importantly, nearly all the FU97 cells treated with the (hexachloro-fluorescein)-T?PP+ conjugate are killed as compared to only half the population of cells in the case of the (hexachloro-fluorescein)-TPP+ conjugate at a similar PDT light dosage. This study thus forms a platform for the healthcare community to explore alternative TPP+ derivatives that can act as optimal drug transporters for enhanced mitochondrially targeted therapies.
- Hu, Zhang,Sim, Ying,Kon, Oi Lian,Ng, Wai Har,Ribeiro, António J. M.,Ramos, Maria J.,Fernandes, Pedro A.,Ganguly, Rakesh,Xing, Bengang,García, Felipe,Yeow, Edwin K. L.
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p. 590 - 599
(2017/02/23)
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- Organoselenium-catalyzed synthesis of oxygen- and nitrogen-containing heterocycles
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A new and efficient approach for the synthesis of oxygen and nitrogen heterocycles by organoselenium catalysis has been developed. The exo-cyclization proceeded smoothly under mild conditions with good functional group tolerance and excellent regioselectivity. Mechanistic studies revealed that 1-fluoropyridinium triflate is key for oxidative cyclization.
- Guo, Ruizhi,Huang, Jiachen,Huang, Haiyan,Zhao, Xiaodan
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supporting information
p. 504 - 507
(2016/02/18)
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- One-Step Synthesis of Substituted Benzofurans from ortho- Alkenylphenols via Palladium-Catalyzed C=H Functionalization
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A dehydrogenative oxygenation of C(sp2)=H bonds with intramolecular phenolic hydroxy groups has been developed, which provides a straightforward and concise access to structurally diversely benzofurans from ortho-alkenylphenols. The reaction is catalyzed by palladium on carbon (Pd/C) without any oxidants and sacrificing hydrogen acceptors.
- Yang, Dejun,Zhu, Yifei,Yang, Na,Jiang, Qiangqiang,Liu, Renhua
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supporting information
p. 1731 - 1735
(2016/06/09)
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- Functionalized phosphonium-based ionic liquids as efficient catalysts for the synthesis of cyclic carbonate from expoxides and carbon dioxide
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A series of novel functionalized phosphonium-based ionic liquids (FPBILs) were synthesized by a simple method, and first evaluated as catalysts for the synthesis of cyclic carbonates through the cycloaddition of CO2 to epoxides in the absence of co-catalyst and solvent. The FPBILs perform well in the cycloaddition reaction, especially the carboxyl-functionalized one. Over [Ph3PC2H4COOH]Br, the yield of propylene carbonate is 97.3% (TOF = 64.9 h-1) at 130 C and 2.5 MPa in 3 h. The synergistic effects of polarization induced by hydrogen bonding and nucleophilic attack of Br-anion account for the excellent performance. Furthermore, the FPBILs with moderate methylene chain length show superior catalytic activity. It is because they have both strong acidity and weak electrostatic interaction between phosphonium cation and halide anion. The strong acidity facilitates the ring-opening of epoxyl, and the weak electrostatic interaction enhances the nucleophilic attack capability of Br -. It is envisaged that the metal- and solvent-free process has high potential for the catalytic conversion of CO2 into value-added chemicals.
- Dai, Wei-Li,Jin, Bi,Luo, Sheng-Lian,Luo, Xu-Biao,Tu, Xin-Man,Au, Chak-Tong
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p. 183 - 188
(2014/01/06)
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- Phosphonium salts and aldehydes from the convenient, anhydrous reaction of aryl acetals and triphenylphosphine hydrobromide
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The reactions of aryl acetals/ketals and triphenylphosphine hydrobromide gave the corresponding aldehydes/ketones and alkyl phosphonium bromides. This reaction was applied to convert acetals/ketals to the corresponding aldehydes/ketones under an anhydrous
- Ramanathan, Mani,Hou, Duen-Ren
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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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- Thermal decomposition of triphenylphosphonium alkyl ester salts
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In thermolyses of molten triphenylphosphonium alkyl ester bromides and chlorides, alkyl = methyl, ethyl, isopropyl, at 130 and 225°C, initial attack of the halide ion on the methyl group gives the methyl halide and ylid 1, Ph3P = CH2, which can be methylated, or is protonated by the phosphonium salt with transylidation giving Ph3P+-CH3X-, X = Br, Cl. The initial reactions of the ethyl or isopropyl esters are with the halide ion, X-, as a base giving ylid, 1, which can be protonated by HX or by transylidation. The t-butyl ester generates Ph3P+-CH3X-but no products of transylidation. The first-formed ylid1, can be trapped by reactive alkyl and acyl halides, and the transient ylidic esters decompose thermally to triphenyl phosphine oxide, Ph3P = O, react further with unreacted phosphonium ester, or are trapped by added aldehyde in a Wittig reaction. The final product compositions are affected by a decrease in pressure, due to escape of volatile intermediates, and by replacement of the X- halide ion by the less nucleophilic and basic tosylate ion. Reactions under reflux, in solution in chloroform, or in suspension in benzene, are similar to those of the molten salts, but yields are generally lower at the lower temperatures. Copyright Taylor & Francis Group, LLC.
- Castaneda, Fernando,Aliaga, Christian,Acuna, Cristina,Silva, Paul,Bunton, Clifford A.
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experimental part
p. 1188 - 1208
(2009/04/16)
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- Fluorinated butanolides and butenolides - Part 9. Synthesis of 2-(trifluoromethyl)butan-4-olides by Wittig reaction using methyl 3,3,3-trifluoropyruvate
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2-(Trifluoromethyl)butan-4-olides 13 and 14 were prepared by a three-step synthesis starting from a Wittig reagent and methyl 3,3,3-trifluoropyruvate (1) as a building block. The Wittig reaction of (2-oxoalkyl)triphenylphosphonium bromides with pyruvate 1 gave intermediate 4-oxobutenoates 8 and 9, which were stepwise selectively reduced with zinc borohydride firstly at the double bond and subsequently at the oxo group to afford unstable 4-hydroxy-2-trifluoromethylalkanoates 11 and 12, which cyclised spontaneously to the end butenolides 13 and 14.
- Palecek, Jiri,Kvicala, Jaroslav,Paleta, Oldrich
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p. 177 - 183
(2007/10/03)
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- Synthesis and biological activity of new diarylalkenes
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Condensation of 5-nitro-, 3-chloro-, and 5-chlorosalicylic acid with formaldehyde afforded dimeric disalicylmethanes which were O-methylated with dimethyl sulfate and oxidized with chromium(VI) oxide to give the diarylketones 10, 11, 12. Wittig reaction with ylides obtained by deprotonation of alkyltriphenylphosphonium salts with sodium bis (trimethylsilyl)amide yielded a series of diarylalkenes. Some of the obtained compounds showed high antimicrobial activity in vitro against Bacillus subtilis and Mycobacterium smegmatis.
- Golebiewski, W. Marek,Cieniecka-Ros?onkiewicz,Szybinska
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- A CONVENIENT SYNTHESIS OF ALKYLPHOSPHONIUM SALTS
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The reaction of methanol and its homologs with Ph3P in 48percent aqueous hydrobromic acid provides alkyltriphenylphosphonium salts in quantitative yields.
- Hercouet, A.,Corre, M. le
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p. 279 - 280
(2007/10/02)
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- SYNTHESES OF UNSYMMETRICALLY SUBSTITUTED DIPYRROMETHANES BEARING A METHANE-CARBON SUBSTITUENT: INITIAL SYNTHETIC APPROACHES TO MESO-(METHOXYCARBONYLMETHYL)-PORPHYRINS RELATED TO CHLOROPHYLLA
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Methods are outlined for the synthesis of unsymmetrically substituted dipyrromethanes bearing an interpyrrolic substituent such as acetate.Condensation reactions between α-unsubstituted pyrroles and pyrrole α-acrylates in glacial acetic acid containing Amberlyst 15 resin and water afford the required acetate substituted dipyrromethanes in good yields; dipyrromethanes with interpyrrolic methyl and ethyl groups are similarly obtained from α-unsubstituted pyrroles and the corresponding α-vinylpyrrole or α-propenylpyrrole.More conveniently, use of the unsubstituted pyrroles and pyrrole acrylates in acetic acid containing a catalytic amount of trifluoroacetic acid gives the dipyrromethanes in good yield.In a model study, use of the MacDonald reaction (5,5'-diformyldipyrromethane condensation with a dipyrromethane-5,5'-dicarboxylic acid affords a 46percent yield of a pure porphyrin (5) in which the meso-acetic side chain is retained intact.
- Burns, Dennis H.,Smith, Kevin M.
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p. 1349 - 1372
(2007/10/02)
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- Untersuchungen im Wittig-System nach einem ordnenden Konzept auf der Basis alternativer Prinzipien
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Our results show that the stereoselectivity of the Wittig-reaction can be controlled by the variation of substituents in accord with the ORDERING CONCEPT OF ALTERNATIV PRINCIPLES (individual pairs, known and unknown classes of alternatives).The "all-phenyl Wittig-system" having three phenyl groups on phosphorous two in ylid- and aldehyd-position was chosen as a standard for our investigations.Differentiation in ylid-position and compensation on phosphorous and aldehyd-position were observed by the comparison of "patterns".Consequently, most of the selectivity rules of Wittig-reactions can be explained by the differentiation through alternatives in the ylid-position.Inversion or conservation of the "patterns" of measured data points to the variation in structure of starting materials, reaction rates and selectivities.Amount-controls were also described in certain systems.
- Bandmann, Heinz,Bartik, Tamas,Bauckloh, Sylvia,Behler, Ansgar,Brille, Frank,et al.
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p. 193 - 204
(2007/10/02)
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- Reaction des oxirannes avec la triphenylphosphine en milieu phenolique
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A new access to the vinylphosphonium salts 4 is proposed, using the reaction of epoxides 1 with triphenylphosphine at 100 deg C in phenol.It succeeds very well for the unfunctional epoxides 1 : 2-monosubstituted and 2,3-disubstituted epoxides.In the case of arylepoxides and 2,2-disubstituted unfunctional epoxides, Wittig and " retro-Wittig " side-reactions decrease the yields in vinylphosphonium salts.The reaction of opening epoxides by triphenylphosphine takes place since 40 deg C and is regio and stereoselective.At 40 deg C, the reaction leads to the formation of β-hydroxy alkylphosphonium salts 3.
- Christol, Henri,Grelet, Danielle,Darvich, Mohammad Raouf,Fallouh, Fayez,Plenat, Francoise,Cristau, Henri-Jean
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p. 477 - 483
(2007/10/02)
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- NOVEL REACTIONS OF PHOSPHONIUM YLIDES WITH PERHALOALKANES: FIRST EXAMPLES OF HALOPHILIC ATTACKS BY PHOSPHONIUM YLIDES AND A FACILE ROUTE TO α-HALOALKYLPHOSPHONIUM SALTS
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Phosphonium ylides Ph3=CHR (R = H, CH3, C2H5, n-C3H7, n-C5H11) react readily with perhalofluoroalkanes to afford regiospecifically α-haloalkylphosphonium salts Ph3P+-CHXR Y- (X = I, Br, Cl) in good yields.These reactions reveal a new type of reactivity phosphonium ylides, i.e., the halophilic attack on C-X bonds, and may be useful for the regiospecific synthesis of substituted haloolefins via Wittig reaction.
- Li, Xing-Ya,Hu, Jin-Shan
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p. 6317 - 6320
(2007/10/02)
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- ARYLATION CATALYTIQUE D'ORGANOPHOSPHORES. PRODUITS DE L'ARYLATION, CATALYSEE PAR LES SELS DE NICKEL (II), DE COMPOSES DU PHOSPHORE TRICOORDINE
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Analysis of the products from the nickel (II) bromide catalysed arylation of tricoordinated phosphorus compounds R2P-Z (Z = H, Cl, SR,NR2) pointed out that this arylation always takes place on phosphorus resulting at first in formation of pseudophosphonium salts.Only the aminophosphonium salts are stable under reaction conditions; the other salts undergo several transformations which can be brought together in a general reactivity scheme to account for all the side products.On regard to other heteroatoms these results point out a particular ability of phosphorus to be arylated under nickel (II) catalysis.The reaction with secondary phosphines can be applied to synthetise diarylphosphonium salts.
- Cristau, Henri-Jean,Chene, Alain,Christol, Henri
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p. 283 - 296
(2007/10/02)
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