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K. Saramma 《Tetrahedron letters》1974,15(32):2775-2776
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Dilithium naphthalene (Li2C10H8) displays a SN2 reactivity profile in its reaction with alkyl fluorides (n-, s- and t-octyl fluoride). SN2 seems to be the dominant mechanism operating with primary alkyl fluorides, which presumably turns into competition with ET as we move to secondary and tertiary alkyl fluorides. Significantly, lithium naphthalene (LiC10H8) seems to have also an important nucleophilic component when reacting with alkyl fluorides, in contrast to the previously proposed general ET process valid for all alkyl halides. These results explain the observed distribution of products and are reinforced by a complete analysis of the products originated by the reaction with 6-halohexenyl radical probes, whose main alkylation products are described here for the first time. 相似文献
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A convergent enantioselective synthesis of panclicin-D has been reported from simple octanal using syn aldol reaction via intramolecular SN2 displacement reaction for the first time towards the construction of anti-β-lactones in panclicin-D. The key steps involved are C-allylation, asymmetric aldolization under Crimmins condition, intramolecular SN2 displacement, and Mitsunobu esterification reaction. 相似文献
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Jonathan T. Reeves Daniel R. Fandrick Zhulin Tan Jinhua J. Song Nathan K. Yee Chris H. Senanayake 《Tetrahedron letters》2009,50(25):3077-5222
Several diethyl 2-cumylmalonates underwent fragmentation and dimerization in PPA at elevated temperatures to give 1,1,3-trimethyl-3-arylindanes in good yields. The same products were obtained from 2-cumylmalonic acid, ethyl 2-cumylcyanoacetate, and 2-cumyl Meldrum’s acid. This represents the first example of an SN1/E1 ionization with diethyl malonate as the leaving group. 相似文献
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Tsunehisa Hirashita Yousuke Hayashi Kazuma Mitsui Shuki Araki 《Tetrahedron letters》2004,45(16):3225-3228
Vinyl and methylindium ate complexes (indates) were prepared and both the tendency of immigration and regioselectivity toward cinnamyl bromide were investigated. The vinyl group was more preferably transferred than the Me group, giving a regioisomeric mixture of SN2 and SN2′ products. The ratio of SN2/SN2′ selectivity can be controlled by solvents; in the presence of polar solvents, such as N-butylpyrrolidone (NBP) and THF, the SN2′ product was mainly obtained, whereas the SN2 product was selectively prepared in solutions containing hexane. The vinylindium compound, generated by the reaction of allylic-type diindium reagents with imine, was also converted to the corresponding vinyl indate, which was allowed to react with allyl chloride to give a three-component coupling product. 相似文献
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Márcio S. Silva 《Tetrahedron letters》2009,50(47):6498-6501
Lithium and magnesium organotellurolates were reacted with lactones producing the corresponding tellurocarboxylic acids. Treatment of the reaction mixture with lithium aluminum hydride allowed the isolation of the corresponding hydroxytellurides in a one-pot operation. 相似文献
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Alexia JonetAlexandra Dassonville-Klimpt Sophie Da NascimentoJean-Michel Leger Jean GuillonPascal Sonnet 《Tetrahedron: Asymmetry》2011,22(2):138-148
Mefloquine derivatives, contrary to chloroquine derivatives have not been widely studied to date. Consequently, mefloquine and its derivatives still remain very attractive synthetic targets. Although mefloquine is usually used clinically as a racemic mixture, some studies have shown that its (+)-enantiomer is more potent than the (−)-enantiomer. Moreover, the (−)-enantiomer is responsible for side effects due to reaction with the central nervous system adenosine receptors, while the (+)-enantiomer does no bind at this binding site. Recently, different libraries of racemic 4-aminoalcohol quinolines showed interesting antimalarial activities. Herein, we describe an enantiopure synthetic and straightforward route to prepare pure enantiomer 4-aminoalcohol quinoline derivatives through a 4-oxirane key-intermediate. A regioselective SN2 ring opening of this epoxide, by diverse amines, allows us to obtain the corresponding (R) or (S) 4-aminoquinolines with good yields and enantiomeric excesses generally superior to 92%. The reported methodology appears suitable for the synthesis of a large number of pure enantiomer 4-aminoalcohol quinoline derivatives. 相似文献
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Concise synthesis of NADH: ubiquinone oxidoreductase (complex I) antagonist pterulinic acid (1a) is reported. The key architectural framework in the natural product, 1-benzoxepine ring skeleton, was smoothly prepared from known salicylaldehyde 2g and phosphorane 3 via tandem SN2/Wittig reaction. Pterulinic acid was prepared in 5 steps from 2g with overall yield of 25%. The versatility of tandem SN2/Wittig reaction was investigated. This tandem reaction tolerated various alkyl, ether, tertiaryamine and nitro substituted salicylaldehyde, and it gave the corresponding 1-benzoxepine ring skeleton in moderated yield (21-72%). 相似文献
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The reaction of dilithium biphenyl (Li2C12H10) with alkyl fluorides has been studied from the point of view of the distribution of products. Two main reaction pathways, the nucleophilic substitution (SN2) and the electron transfer (ET), can compete to yield the same alkylation products in what is known as the SN2-ET dichotomy. SN2 seems to be the main mechanism operating with primary alkyl fluorides (n-RF). Alkylation proceeds in good yields, and the resulting alkylated dihydrobiphenyl anion (n-RC12H10Li) can be trapped with a second conventional electrophile (E+) affording synthetically interesting dearomatized biphenyl derivatives (n-RC12H10E). The reaction gives a higher amount of ET products as we move to secondary (s-RF) and to tertiary alkyl fluorides (t-RF), in which case the mechanism seems to be dominated by ET. In this case, alkylation by radical coupling is still feasible, giving access to the synthesis of t-RC12H10E, although in lower yields. A rational interpretation of this SN2-ET dichotomy is given on the basis of the full distribution of products observed when 5-hexenyl fluoride and 1,1-dimethyl-5-hexenyl fluoride were are used as radical probes in their reaction with Li2C12H10 and LiC12H10. 相似文献
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Application of the configuration mixing model to the SN2 reaction illustrates that charge development in an SN2 reaction is not linearly related to the position of the transition state along the reaction coordinate. 相似文献
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Chuangxing Guo Liming DongJoseph Marakovits Susan Kephart 《Tetrahedron letters》2011,52(14):1692-1696
Here we report mild, environmentally-friendly reaction conditions which enable the addition-elimination SNAr reaction between weakly reactive substrates--an aminopyrrolopyrazole template and several substituted pyrimidines. The method was developed during our efforts to synthesize a series of novel P21-activated kinase (PAK) inhibitors. 相似文献
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Paul Baybutt 《Chemical physics letters》1975,30(2):293-295
Ab initio SCF MO calculations have been performed for the reactants, products and reaction complex in the title reaction. The influence of diffuse and polarization basis functions in determining the presence of a reaction barrier was investigated. No barrier to the forward or reverse reactions was found. 相似文献
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This paper is devoted to a detailed theoretical study of an ion pair SN2 reaction LiNCO+CH3F in the gas phase and in solution at the level of MP2(full)/6-31+G**//HF/6-31+G**. Two possible reaction mechanisms, inversion and retention, are discussed. There are eight possible reaction pathways. The inversion mechanism is more favorable no matter in the gas phase or in solution based on analyses of the transition structures. Methyl isocyanate should form preferentially in the gas phase and more stable methyl cyanate is the main product in solution. The retardation of the reaction in solvents was attributed to the difference in solvation in the separated reactants and in the transition state. 相似文献
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Cédric Kalinski Michael Umkehrer Nadine Jäger Wolfgang Hiller 《Tetrahedron letters》2006,47(12):2041-2044
A combinatorial synthetic route yielding fused tetrazolo[1,5-a]quinoxalines is described. The use of 2-fluorophenylisocyanide in the Ugi-tetrazole reaction (tetrazole-U-4CR) followed by a nucleophilic aromatic substitution (SNAr) affords the tricylic tetrazolo[1,5-a]quinoxaline moiety in good yields and with high diversity. 相似文献