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31.
Novel 3-phenyl- and 3-(4-nitrophenyl)cyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-diones and the corresponding imino derivatives 5a,b and 6a,b were synthesized in modest to moderate yields by the abnormal and normal aza-Wittig reaction of 2-(1,3-diazaazulen-2-ylimino)triphenylphosphorane with aryl isocyanates and subsequent heterocyclization reaction with a second isocyanate. The related cationic compound, 1-methyl-3-phenylcyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-dionylium tetrafluoroborate 7a, was also prepared. The electrochemical reduction of these compounds exhibited more positive reduction potentials as compared with those of the related compounds of 3,10-disubstituted cyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1H,3H)-dione systems. In a search of the oxidizing ability, compounds 5a, 6a, and 7a were demonstrated to oxidize some amines to give the corresponding imines in more than 100% yield under aerobic and photo-irradiation conditions, while even benzylamine was not oxidized under aerobic and thermal conditions at 100 °C. The oxidation reactions by cation 7a are more efficient than that by 5a and 6a. Quenching of the fluorescence of 5a was observed, and thus, the oxidation reaction by 5a probably proceeds via electron-transfer from amine to the excited singlet state of 5a. In the case of cation 7a, the oxidation reaction is proposed to proceed via formation of an amine-adduct of 7a and subsequent photo-induced radical cleavage reaction. 相似文献
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Pyrido[2,3-d]pyrimidines are synthesized in a two-step procedure from amides and tetrazolo[1,5-a]pyridine-8-carbonyl chloride. Reaction of the crude imides with triphenylphosphine effects an intramolecular aza-Wittig reaction to afford a variety of substituted pyrido[2,3-d]pyrimidines in good to moderate yields (30-76%). 相似文献
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Cyclodehydration of a linear tripeptide furnished the first total synthesis of asperlicin D in moderate yield. The cyclodehydration process was triggered by an intramolecular nucleophilic acyl substitution and an intramolecular aza-Wittig reaction. 相似文献
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An abnormal aza-Wittig reaction was observed when resin-bound iminophosporanes were treated with aryl isocyanates on the solid-phase. The mechanism of the reaction may involve the loss of triphenylphosphinimide instead of triphenylphosphinoxide, resulting in the formation of isocyanates instead of carbodiimides as intermediates. The selectivity of the abnormal aza-Wittig reaction versus the normal aza-Wittig reaction was shown to be strongly dependent on the reaction temperature and the nature of the aryl isocyanate employed. Optimization studies revealed that employing electron poor aryl isocyanates at high temperature leads to 95% of abnormal aza-Wittig product. The reaction was used for the parallel solid-phase synthesis of 3-aryl-2,4-dioxo-1,3,5-triazino[1,2-a]benzimidazoles. 相似文献
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应用芳基异氰酸酯与烯基膦亚胺1的氮杂Wittig反应, 得到的碳二亚胺2, 再与水合肼作用得到氨基咪唑啉酮衍生物4. 而后用4与芳基异氰酸酯(或酰氯)、三苯基膦、六氯乙烷和三乙胺“一锅”反应, 得到4,5-二氢咪唑并[1,2-b]-1',2',4'-三唑-4-酮衍生物6或7. 探讨了所合成新型稠杂环化合物的生物活性, 结果表明部分化合物表现出良好的杀菌活性. 如7c在50 mg/L浓度时, 对棉花枯萎菌、稻瘟菌、黄瓜灰霉菌和油菜菌核菌的抑制率均达100%. 相似文献
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Azizeh Ahmadi Azra Bagherzadeh Yavar Ahmadi Hamideh Ahankar 《Phosphorus, sulfur, and silicon and the related elements》2016,191(6):871-875
The 1:1 imine intermediate generated by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane in the presence of 3-phenyl-2-propynoic acid and the corresponding iminophosphorane intermediate was formed. Disubstituted 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed in neutral conditions at room temperature (18–26°C). The disubstituted 1,3,4-oxadiazole derivatives were produced in excellent yields. 相似文献
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《Mendeleev Communications》2022,32(5):634-636
A general synthesis of NH-isatin N′-arylimines involves the aza-Wittig reaction of isatin and aryl azides, providing higher E-diastereoselectivity as compared to previously described methods. The procedure is applicable even to anilines which do not directly react with isatins. 相似文献
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Reactions of (N-isocyanimino)triphenylphosphorane with aromatic bis-aldehydes (isophthalaldehyde and terphthalaldehyde) in the presence of aromatic (or heteroaromatic) carboxylic acids proceed smoothly at room temperature and in neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in good yields. The reaction proceeds smoothly and cleanly under mild conditions, and no side reactions were observed.