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The treatment of O-alkyllactonium tetrafluoroborate salts with anh. NaSH in CH3CN at 0°C led to five-, six-, and seven-membered thionolactones (44– 90% yield). 相似文献
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Novel 2-(5-R-1,3,4-thiadiazol-2-yl)aminothiazolin-4-ones 6a—h and 2-imino-3-(5-R-1,3,4-thiadiazol-2-yl)thiazolidin-4-ones 7a—h were prepared by treating N-(5-R-1,3,4-thiadiazol-2-yl)thioureas 4a—h with chloroacetic acid on various solid supports under microwave irradiation. Tautomeric mixtures of compounds 6a—h and 7a—h were obtained in all cases. In alkaline and neutral media, compounds 6a—h were the major products, while in acid media, 7a—h were the major products. 相似文献
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K. Soga S. Hosoda S. Ikeda 《Journal of polymer science. Part A, Polymer chemistry》1979,17(2):517-529
A detailed study has been carried out on the new synthetic reaction of poly(p-xylylene carbonate) from potassium carbonate and p-xylylene dibromide by using a variety of crown ethers as a catalyst, which was recently found by the present authors. Crown ethers having 18-member ring showed the best catalytic property of the various crown ethers, and the reaction was conducted in various solvents at 50–160°C by using 18-crown-6-ether. Both the polymer yield and the molecular weight of the polymer increased in proportion to the amount of potassium carbonate, and they increased rapidly and reached constant values with increasing the concentration of 18-crown-6-ether. They also depended significantly upon the reaction temperature as well as the solvent used. A maximum yield with the highest molecular weight was obtained from the reaction at 100–120°C in diglyme solvent. The spectroscopic analysis of the polymer indicated that all the end groups of the resulting polymer had the structure of benzyl bromide. From these results, a plausible mechanism was proposed for the reaction. Similar reactions were also conducted by using several aliphatic dibromides, Br? (CH2)x? Br, in place of p-xylylene dibromide. The products were strongly dependent of the value of x: polycarbonate was obtained from dibromides with ≧4, and cyclic carbonates from dibromides with ≦3. 相似文献
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A new synthetic route to trimethylgallium was developed. It is based on preparation of gallium methyl derivatives by the Green reaction, followed by their alkylation with methyl Grignard reagent. The suggested procedure is well reproducible, with the yield of pure trimethylgallium exceeding 90%. 相似文献
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The reactions of R2PPR2 (R = Me, Et, Ph) and (MeP)5 with Me3−nAs(NMe2)n (n = 1, 2, 3) and of Me2PPMe2 with Me2AsNR′2 (R′ = Et, Prn, and Pri) were investigated as a function of time at room temperature using 1H and 31P NMR spectroscopy. For the diphosphine/Me2AsNR′2 reactions, the NMR spectral data suggest a reaction pathway involving the initial formation of R2PAsMe2 and the respective acyclic dialkylaminophosphine, R2PNR′2. The P---As intermediate then symmetrizes to R2PPR2 and Me2AsAsMe2, the parent aminoarsine is completely consumed, and additional R2PNR′ is formed. The relative rate of aminophosphine production is dependent upon the nature of the substituent on the phosphorus and nitrogen atoms. For systems involving MeAs(NMe2)2 and As(NMe2)3 as reactants, the intermediates could not be characterized, but the products were the expected aminophosphine and (MeAs)5 or elemental arsenic, respectively. (MeP)5 reacts to give MeP(NMe2)2 and the expected As---As bonded species. A comparison of the reactivity of these systems with analogous diarsine/aminoarsine systems is discussed. The results of the NMR study were utilized in designing a convenient, high yield, synthetic route to acyclic aminophosphines. 相似文献
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An efficient strategy is described for the synthesis of enantiopure calystegine alkaloids. The key step employs a zinc-mediated fragmentation of benzyl-protected methyl 6-iodo-glycosides followed by in situ formation of the benzyl imine and Barbier-type allylation with zinc, magnesium, or indium metal. Stereochemistry in the pivotal allylation is controlled by the choice of the metal. The functionalized 1,8-nonadienes, thus formed, are converted into cycloheptenes by ring-closing olefin metathesis. Regioselective hydroboration and oxidation give the corresponding cycloheptanones, which are deprotected to afford the desired calystegines. Hereby, calystegine B(2), B(3), and B(4) are prepared from D-glucose, D-galactose, and D-mannose, respectively. This route constitutes the shortest synthesis of calystegine B(2) and gives rise to the first total syntheses of calystegine B(3) and B(4). 相似文献
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Toshiro Ibuka Yoshinori Mitsui Kenji Hayashi Hiroyuki Minakata Yasuo Inubushi 《Tetrahedron letters》1981,22(44):4425-4428
A stereoselective synthesis of -(6S,7S,8S) -7-butyl-8-hydroxy-1-azaspiro[5.5]undecan-2-one, a key intermediate for the synthesis of perhydrohistrionicotoxin, was described. 相似文献
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Deyan Zhang 《Journal of fluorine chemistry》2009,130(10):938-1177
The synthesis of polyfluorinated benzyl alcohol from pentafluorobenzoic acid has been developed. An economical and effective direct reduction method of polyfluorobenzoic acid by zinc borohydride is described. 相似文献
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Anne-Laure Gérard 《Tetrahedron letters》2007,48(23):4123-4126
A facile method for the synthesis of new pyrazoloisoindolones via a Suzuki cross-coupling reaction using a pyrazolylboronic ester is described. 相似文献
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A general strategy for the preparation of enediyne-bridged amino acids has been disclosed. A cross-coupling reaction between amino- and carboxyl-modified amino acids under Sonogashira reaction conditions gave a protected enediyne-peptide conjugate. The model obtained can be used as a template in studies of Bergman cycloaromatization or peptide conformational preferences induced by the presence of the enediyne moiety. 相似文献
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Preparation of novel cyclopent-3-ene-1,2-dione dimers from γ-substituted crotonate esters and dimethyl oxalate by vinylogous double Claisen condensations has given access to a series of polyfunctional cyclopentane derivatives potentially useful in synthesis. 相似文献
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The Michael-addition of polyfluoroalkenoates with thiophenols in acetonitrile in the presence of Na-HCO3 yielded the corresponding addition products, which were further treated with polyphosphoric acid (PPA) to give a series of new fluorine-containing thiochromones in good yields. 相似文献
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A short synthetic strategy for preparation of the conduritols is described. The key step employs a zinc-mediated fragmentation of protected methyl 5-deoxy-5-iodo-d-pentofuranosides followed by an allylation of the intermediate aldehyde in the same pot. The allylation is performed with 3-bromopropenyl benzoate and occurs with good diastereoselectivity. An amino group can be introduced in the product by trapping the intermediate aldehyde as the imine prior to the allylation. The functionalised 1,7-octadienes, thus obtained, are converted into protected conduritols by ring-closing olefin metathesis. 相似文献
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Krishnakumar KS Goudedranche S Bouchu D Strazewski P 《The Journal of organic chemistry》2011,76(7):2253-2256
We are reporting on the utility of commercial vinyl isocyanate for a practical synthetic route from adenosine to N(6)-bis-demethylpuromycin in seven steps and 65% overall yield. A clean one-pot conversion of 3'-bromo-2'-carbamoyl derivative 8 to 3'-amino-3'-deoxyadenosine derivative 10 is the main feature of this synthetic pathway. This synthesis is the shortest synthetic route toward 3'-(aminoacylamido)deoxyadenosines to date. 相似文献