二乙基膦酰乙酸乙酯阴离子参与脂肪族SRN1反应

二乙基膦酰乙酸乙酯阴离子与对硝基苄基衍生物的反应中发生烷基化和烷氧基化.结果表明,离去基团的离去性能降低,SN2烷基化或烷氧基化受抑制,而是有利于SRN 1途径,使烷基化容易发生.在对硝基苄基氯化物与阴离子反应时,得到P,P'-二硝基苯代乙烯,当不存在电子转移抑制剂或只存在间二硝基苯时,二苯代乙烯通过SRN 1机理形成,在对二硝基苯时,以SN 2消除反应机理.     

硝基烷基膦酸酯碳负离子烷基化反应区域选择性研究

α-或β-硝基烷基膦酸酯双负离子与卤代烷反应, 生成碳-烷基化产物, 反应区域选择性取决于硝基膦酸酯的结构, 讨论了可能的反应机理。     

2,2-disubstituierte cyclopentan-1,3-dione—2: Untersuchung der regioselektivität von alkylierungs-reaktionen an 2-methyl-cyclopentan-1,3-dion

The regioselectivity of the alkylation of alkali metal salts of 2 - methyl - cyclopentane - 1,3 - dione with alkyl halides depends significantly on the structure of the alkylating reagent and the type of solvent used in the reaction. Unsubstituted saturated primary alkyl halides with the exception of methyl iodide preferentially yield products of O-alkylation. Alkyl halides with an sp²- or sp-hybridized carbon atom in a β-position preferentially yield products of C-alkylation. Dipolar aprotic solvents favour O-alkylation; water favours C-alkylation. On the basis of these results procedures for the prepartion of 2-allyl-2-methyl-, 2-allyl-2-ethyl-, 2-methyl-2-propargyl- and 2 - benzyl - 2 - mehtyl - cyclopentane - 1,3 - dione have been developed. The alkylation of 2 - methyl - cyclopentane - 1,3 - dione with methyl bromoacetate was also intensively investigated.     

Reaction of iodotrinitromethane with unsaturated compounds

Conclusions The reaction of iodotrinitromethane with olefins takes place by both the O- and the C-alkylation scheme, in which connection the direction of the reaction depends on the structure of the olefin and on the solvent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 621–625, March, 1968.     

Multicomponent, one-pot sequential synthesis of 1,3,5- and 1,3,5,5-substituted barbiturates

Carbodiimides and malonic acid monoethylesters readily react to afford N-acylurea derivatives that could be cyclized in situ by addition of a suitable base. This process represents a general and straightforward one-pot sequential synthesis of 1,3,5-trisubstituted barbiturates in very mild conditions (organic solvent/2 N NaOH aqueous solution, 20 degrees C). Performing the reaction in the presence of an electrophile resulted in the formation of fully substituted (namely, 1,3,5,5-tetrasubstituted) barbiturates through a three-component one-pot sequential process. The latter, however, occurred only with highly reactive electrophiles, such as benzyl and, in some instances, allyl halides. In order to expand the scope of the process, we sought to develop a general method for the C-alkylation of 1,3,5-trisubstituted barbiturates. We found that C-alkylation occurred upon treatment of 1,3,5-trisubstituted barbiturates with an alkyl halide in CH3CN at 120 degrees C in the presence of anhydrous K2CO3 affording the target 1,3,5,5-tetrasubstituted barbiturates in good yields. The multicomponent process was accomplished by combining the three steps in a one-pot sequential fashion, i.e., the condensation of carbodiimides with malonic acid monoethylesters, the cyclization of the resulting N-acylureas, and the C-alkylation of the resulting 1,3,5-substituted barbiturates. A detailed study of the influence of the structure of the reactants on the reaction outcome and mechanism is presented. By selective N'-deprotection of 1,3,5,5-tetrasubstituted barbiturates, the corresponding 1,5,5-trisubstituted barbiturates were also prepared.     

Unmodified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanostructure promoted with external magnetic field: safe,magnetically recoverable,and efficient nanocatalyst for N- and C-alkylation reactions in green conditions

Transition metal compounds have emerged as suitable catalysts for organic reactions. Magnetic compounds as soft Lewis acids can be used as catalysts for organic reactions. In this report, the Fe₃O₄ nanostructures were obtained from Fe²⁺ and Fe³⁺-salts, under an external magnetic field (EMF) without any protective agent. The X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy tools were used to characterize these magnetic compounds. The two-dimensional (2-D, it showed nanometric size in the two dimensions, nanorod structure) Fe₃O₄ compound showed high catalytic activity and stability in N- and C-alkylation reactions. A diverse range of N- and C-alkylation products were obtained in moderate to high yield under green and mild conditions in air. Also the N- and C-alkylation products can be obtained with different selectivity and yield by exposure reactions with EMF. Results of alkylation reactions showed that the presence of Fe(II) and Fe(III) species on the surface of magnetic catalysts (phase structure of magnetic compounds) are essential as very cheap active sites. Also, morphology of magnetic catalysts had influence on their catalytic performances. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The catalyst was reused at least four times without any loss of its high catalytic activity for N- and C-alkylation reactions.     

Catalytic alkylation of pyrocatechol with camphene

Regularities of the pyrocatechol alkylation with camphene in the presence of aluminum-containing homogeneous catalysts and heterogeneous acid catalysts were studied. The effect of the catalyst type on the reaction selectivity and the product composition was established. The most selective heterogeneous catalyst for the C-alkylation of pyrocatechol is montmorillonite KSF, which leads to a rearrangement of the terpene fragment to isocamphyl structure. Homogeneous organoalyuminum compounds are found to be nonselective catalysts for the alkylation of pyrocatechol at the benzene ring.     

Zn-promoted regioselective and sequence-selective one-pot joining reaction of three components: alkyl iodides, alpha,beta-unsaturated esters (or nitriles), and acylating agents

One-pot treatment of alkyl iodides, alpha,beta-unsaturated esters (or nitriles), and acylating agents such as nitriles or acid anhydrides in the presence of Zn metal at room temperature in the same reaction system brought about a regioselective and sequence-selective three-component joining reaction involving first C-alkylation at the beta-position and second C-acylation at the alpha-position of alpha,beta-unsaturated esters (or nitriles) to afford the corresponding alpha,alpha-dialkylketoesters (or alpha,alpha-dialkylketonitriles) in moderate to good yields. [reaction: see text]     

Synergistic mechanisms of β-diketone derivatives and zinc-calcium soaps in PVC stabilisation

It has been possible to explain the mechanisms of stabilisation and of the synergistic effects of the β-diketone derivatives claimed in a patent as new stabilisers for improving the efficiency of those recipes based upon zinc and calcium soaps in the prevention of the initial discoloration of poly(vinyl chloride).Using chlorohexene as a model compound for allylic chloride structures and benzoylacetone as a model compound for enolised β-diketone derivatives, it has been shown that the benzoylacetone can substitute allylic chlorine atoms through a C-alkylation reaction which takes place only in the presence of ZnCl₂ as catalyst. This reaction drastically changes the percentage of the enol and causes the appearance of two bands at 1720 cm^?1 and 1680 cm^?1 in the infra-red spectrum due to the ketonic structures During the processing of the PVC on a rolling mill at 180°C in the presence of zinc and calcium stearates and benzoylacetone there is grafting of the ketone derivative through a C-alkylation reaction. There is a closed parallelism between the influence of the benzoylacetone on the dehydrochlorination of the chlorohexene and on the accumulation of chloride ions in the polymer matrix in the presence of zinc and calcium stearate. The synergistic effect of the benzoylacetone in the prevention of the initial discoloration is related to the substitution reaction through a C-alkylation which takes place only in the presence of zinc stearate which generates ZnCl₂ which, in turn, acts as a catalyst for both the C-alkylation and dehydrochlorination.     

Chemoselectivity in the microwave-assisted solvent-free solid-liquid phase benzylation of phenols: O- versus C-alkylation

The outcome of the solvent-free benzylation of phenol and 4-substituted phenols (such as 4-cresol and 4-chlorophenol) under MW irradiation was found to depend on the absence or presence of the base (K₂CO₃) and catalyst (triethylbenzylammonium chloride (TEBAC)). Reaction of benzyl halides at 80-120 °C in the presence of K₂CO₃ and TEBAC resulted in O-alkylation in high (89-96%) chemoselectivities. In the absence of TEBAC, the proportion of C-alkylation was considerable (16-34%). Omitting also K₂CO₃ from the reaction mixture, C-alkylation became predominant. In the case of 4-tert-butylphenol, the presence of TEBAC promoted C-alkylation. The selectivity of the alkylations can be fine-tuned by choosing the appropriate conditions.     

Base-promoted reactions of bridged ketones and 1,3- and 1,4-haloalkyl azides: competitive alkylation vs azidation reactions of ketone enolates

The reactions of 1,3- and 1,4-haloalkyl azides with enolates of 2-norbornanone (and a ring-expanded analog) afford polycyclic 1,2,3-triazolines in good yields. The reaction occurs by the initial azidation of the ketone enolate, followed in order by triazoline formation and O-alkylation. An interesting element of this process is the preferential reaction of the alkyl azide with an enolate anion as opposed to the more familiar reaction of the alkyl halide (including Cl and I derivatives). Reactions of acyclic or monocyclic enolates generally lead to 1,2,3-triazoles but none of the alternative C-alkylation product.     

Effet de solvant sur support solide:régiosélectivité de l'alkylation des énolates de l'acétylacétate d'éthyle par le sulfate d'éthyle en présence de “hmpt solide”

The reaction of Li, Na, K enolates of ethylaceto acetate with diethylsulfate in THF at room temperature gives 60–70% O-alkylation when performed in the presence of one molar equivalent of solid HMPA. Without HMPA, in the same conditions, Li enolate docs not react, Na enolate only gives C-alkylation while K enolate leads to 90% C-alkylation, the reactions being quite slower in the two latter cases. The effects of one molar equivalent of solid and liquid HMPA are compared: for the K enolate the reaction is faster and the degree of O-alkylation higher with solid HMPA; practically no difference is seen for Na enolate, while the reverse is observed with the Li enolate. The cooperative effect of the polymer should thus only work for a sufficiently large cation, as the Li enolate is fixed on the solid HMPA in a larger amount than the K enolate. The study of this reaction is proposed to test the efficiency of other “solid solvents” interacting strongly with cations.     

Contrasting behaviour of TCNE and TCNQ zwitterionic benzoquinonemonoimine derivatives and coordination of a tricyanoethenyl substituent to Pd(0)

The reaction of TCNE and TCNQ zwitterionic benzoquinonemonoimine derivatives under basic conditions resulted in HCN elimination to give a tricyanoethenyl derivative - which forms a π-complex with Pd(0)--or a stable malodinitrile salt, respectively. In the latter case, chemoselective C-alkylation was observed whereas oxidation led to dimerization by C-C coupling.     

Divergent regioselectivity in the base-promoted reactions of cyclic eight-membered alpha-ketols with activated halides

[reaction: see text] Deprotonation of 2-hydroxycyclooctanone followed by exposure to an allylic or benzylic halide proceeds very selectively to give the product of C-alkylation. The effect of Delta(5,6)-unsaturation is to promote instead the formation of the O-alkylated derivative. This crossover in kinetic preference is attributed to an inability of the olefinic system to attain a conformation conducive to proton abstraction at C-2.     

Réactions SRN1 d'agents alkylants anthraquinoniques

The C-alkylation reaction of three reductive alkylating agents prepared from 2-methylanthraquinone by 2-nitropropane anion is shown to proceed by the S_RN1 mechanism. The S_RN1 mechanism is confirmed by the leaving group effect and the inhibitory effects of dioxygen, p-dinitrobenzene, cupric chloride and di-tert-butylnitroxide. This reaction can be extended to 1-methyl-3-nitropyrrolidin-2-one anion.     

Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts

The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO₄ (Al/P=1), Al₂O₃ and AlPO₄-Al₂O₃ (5–25 wt.% Al₂O₃) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.     

Synthesis and Properties of N-(2,2,2-Trichloroethylidene)trifluoromethanesulfonamide and Its Derivatives

The reaction of N,N-dichloromethanesulfonamide with trichloroethylene gave N-(2,2,2-trichloro- ethylidene)trifluoromethanesulfonamide which showed high reactivity toward oxygen- and nitrogen-centered nucleophiles, as well as in C-alkylation of aromatic compounds.     

Benzyl p-Toluenesulphonate as an 0-Benzylating Agent for the Protection of Phenols

Benzylation is a popular method of protecting phenolic groups during synthetic procedures. Benzyl ethers are stable to basic and mildly acidic conditions, but are cleaved readily by stronger acid, reduction, or most commonly by hydrogenolysis¹. Current methods of converting phenols into O-benzyl derivatives rely principally on the use of commercially available benzyl chloride or benzyl bromide and usually involve heating a mixture of the phenol and the halide with anhydrous potassium carbonate in dry acetone or DMF¹. To increase reactivity of the halide, potassium iodide may be added to the reaction mixture to generate benzyl iodide ‘in situ’. A major disadvantage of using alkyl halides in the preparation of phenolic ethers is the amount of simultaneous C-alkylation which can occur. Whilst C-alkylation is reduced by using polar aprotic solvents¹, it may still become an important side reaction during the alkylation of phenols containing phloroglucinol substitution patterns, yields of 0-alkyl derivatives decreasing markedly, and a complicated mixture of products generally ensues. In the cases of 0-methylation or -ethylation, such unwanted side-reactions can be minimised by employing dimethyl sulphate as the alkylating agents instead of the halides. No similar agents have been available for 0-benzylation reactions.     

Reductive Activation of Arenes: XIV. Effect of Medium on the Products Ratio in the Alkylation of Nitrobenzene Radical Anion Sodium Salt

The product of nitrobenzene reduction by 1 equiv of sodium reacted with tert-butyl iodide in liquid ammonia and its mixtures with tetrahydrofuran and hexamethylphosphoramide to afford a mixture of compounds alkylated either by the functional group (N-alkylation) or at the benzene ring (C-alkylation). The ratio of N- and C-alkylation products decreases in the solvents series NH₃-THF (5.7) > NH₃ (1.0) > NH₃-HMPA (0.6).     

相转移催化不对称碳烷化研究—光学活性的二氢吲哚酮类衍生物的合成

本文报道了手性季铵盐1-7催化溴代烷与1,3-二甲基-5-甲氧基-2-二氢吲哚酮(8)的不对称3-C烷化反应, 并通过研究不同的催化剂结构、溶剂、温度及溴代烷结构对产物光学活性的影响, 讨论了不对称诱导机理.