共查询到20条相似文献,搜索用时 31 毫秒
1.
[reaction: see text] An efficient synthesis of dityrosine and the first syntheses of the tyrosine trimers trityrosine and pulcherosine have been achieved. Protected 3-iodotyrosine underwent tandem Miyaura borylation-Suzuki coupling to give protected dityrosine. The choice of benzyl carbamate, ester, and ether protecting groups enabled a one-step global deprotection to give dityrosine. Suzuki coupling of protected 3,5-diiodotyrosine and tyrosine-3-boronic acid derivatives gave the corresponding trityrosine, but in low yield. However, use of a potassium tyrosine-3-trifluoroborate derivative in place of the corresponding pinacol boronate ester, in combination with protecting group variation, gave protected trityrosine in good yield. Access to pulcherosine was achieved through copper-catalyzed coupling of phenylalanine-4-boronic acid and 4-O-protected dopa derivatives to give an isodityrosine derivative. Selective halogenation followed by Suzuki coupling with the potassium tyrosine-3-trifluoroborate gave protected pulcherosine. Global deprotection of the protected trityrosine and pulcherosine derivatives completed the first syntheses of the corresponding tris-alpha-amino acids. 相似文献
2.
Suzuki偶联反应是构筑碳-碳单键的重要方法之一。 继有机硼酸后,有机三氟硼酸盐成为一种理想的、具有研究意义和使用价值的有机硼亲核试剂。 本文系统地综述了有机三氟硼酸钾参与的Suzuki偶联反应研究进展并对其研究前景进行了展望。 相似文献
3.
4.
Prashi Jain Shuyan Yi Patrick Thomas Flaherty 《Journal of heterocyclic chemistry》2013,50(Z1):E166-E173
This article focuses on the utility of organotrifluoroborate salts as coupling partners for Suzuki–Miyaura cross‐coupling with 4‐nitro‐6‐triflyl benzimidazoles using microwave irradiation. The C–C bond formation at the 6‐position of the electron‐rich 1‐,4‐,6‐trisubstituted benzimidazole core is challenging and was not achievable via Kumada, Negishi, Stille, or Heck coupling strategies. Yields of 37–70% could be obtained via palladium coupling strategies utilizing potassium benzyl trifluoroborates as the organometallic coupling partner. 相似文献
5.
A simple,quick and novel protocol for biaryl synthesis using LiCl‐promoted in situ‐generated Pd nanoparticles 下载免费PDF全文
Parmita Phukan Preeti Rekha Boruah Praveen Singh Gehlot Arvind Kumar Diganta Sarma 《应用有机金属化学》2018,32(2)
This paper describes a simple and a very quick protocol for biaryl synthesis using the Suzuki–Miyaura cross‐coupling reaction. A quintessential role of salting‐out agent LiCl was observed in the Suzuki–Miyaura cross‐coupling reaction that enhanced the reduction rate of Pd (II) to a considerable extent, resulting in the formation of nanosized palladium in a few seconds. The isolated Pd nanoparticles were characterized with X‐ray diffraction, dynamic light scattering, TGA, transmission electron microscopy and scanning electron microscopy‐dispersive X‐ray spectroscopy. The Suzuki–Miyaura cross‐coupling reaction proceeded very well with the in situ‐generated Pd nanocatalysts furnishing the desired biaryl adducts with excellent yields. 相似文献
6.
A series of poly(9,9-dihexylfluorene)s (PDHFs) have been synthesized via microwave-assisted Suzuki and Yamamoto coupling reactions. Compared with the conventional oil-bath heating (48 h, Mw 20100 g/mol by Suzuki reaction and Mw 24000 g/mol by Yamamoto reaction), microwave-assisted polymerization can yield PDHFs with higher molecular weights (Mw 37200 g/mol by Suzuki reaction and Mw 43400 g/mol by Yamamoto reaction) in shorter time (14 and 60 min). However, sometimes formation of insoluble gels was observed together with PDHF in Suzuki coupling reaction. PDHF and insoluble gels were analyzed by XPS, elemental analysis, FTIR, TGA and DSC. Experimental results demonstrated that H2O might take part in the Suzuki coupling reaction under microwave condition, which could make the cross-linking reaction occur and form gels. 相似文献
7.
Muddasir Hanif LU Ping ZHENG Yan LI Mao XIE Zeng-qi MA Yu-guang LI Di LI Jing-hong 《高等学校化学研究》2008,24(1):110-115
Suzuki coupling reaction is widely used in the construction of conjugated polymers; however, there is still no report describing the mechanism and coupling of 9,10-phenanthrenequinone(PQ) building blocks via Suzuki reaction because PQ is sensitive to bases and light. Herein is reported the efficient Suzuki coupling of PQ with 9,10-dialkylfluorene with Na2CO3 as basic species and high molecular weight PQ-Alt-Dialkyl-Fluorene conjugated copolymer obtained in an yield of 42%. Based on the characterization data and well-accepted literature, we proposed a step-by-step mechanistic explanation for the formation of the PQ containing alternating conjugated copolymer. 相似文献
8.
Xiaokang Ren Qianli Zou Chengqian Yuan Rui Chang Ruirui Xing Xuehai Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):5930-5934
In diverse biological systems, the oxidation of tyrosine to melanin or dityrosine is crucial for the formation of crosslinked proteins and thus for the realization of their structural, biological, and photoactive functionalities; however, the predominant factor in determining the pathways of this chemical evolution has not been revealed. Herein, we demonstrate for tyrosine‐containing amino acid derivatives, peptides, and proteins that the selective oxidation of tyrosine to produce melanin or dityrosine can be readily realized by manipulating the oxygen concentration in the reaction system. This oxygen‐dependent pathway selection reflects the selective chemical evolution of tyrosine to dityrosine and melanin in anaerobic and aerobic microorganisms, respectively. The resulting melanin‐ and dityrosine‐containing nanomaterials reproduce key functions of their natural counterparts with respect to their photothermal and photoluminescent characteristics, respectively. This work reveals the plausible role of oxygen in the chemical evolution of tyrosine derivatives and provides a versatile strategy for the rational design of tyrosine‐based multifunctional biomaterials. 相似文献
9.
3,5-Dichloroisothiazole-4-carbonitrile 1 react with aryl- and methylboronic acids to give in high yields the 3-chloro-5-(aryl and methyl)-isothiazole-4-carbonitrile 2 regiospecifically. The reaction was optimized with respect to base, phase transfer agent and palladium catalyst. Suzuki coupling at C-5 was also achieved in high yield using potassium phenyltrifluoroborate. The regiospecificity of either coupling method is maintained with 3,5-dibromoisothiazole-4-carbonitrile 4 to give exclusively 3-bromo-5-phenylisothiazole-4-carbonitrile 5. Suzuki cross-coupling conditions applied to 3-chloro-5-phenylisothiazole-4-carbonitrile 2a gave 3-phenoxy-5-phenylisothiazole-4-carbonitrile 6, which was prepared independently, and not the 3-phenyl derivative. All isothiazole products were fully characterized. 相似文献
10.
Previously reported polymer-supported oxime palladacycle catalyst has shown effective catalytic activity in the Suzuki coupling reaction. In this work, the effect of microwave on reaction rate and induction period was examined by comparing them with the conventional heating. Undoubtedly, microwave heating effectively enhanced the catalytic performance in the Suzuki reaction. In-depth observation of the kinetic profiles revealed that the microwave irradiation not only reduced the overall reaction time but also significantly decreased the induction period to less than 3 min. Finally, the performance of the catalyst in water, coupling of potassium phenyltrifluoroborate and aryl bromides, and recyclability were also examined. 相似文献
11.
[reaction: see text] The ligandless palladium-catalyzed Suzuki cross-coupling reaction of potassium aryl- and heteroaryltrifluoroborates with aryl- or heteroaryl halides or triflates proceeds readily with very good yields. The cross coupling can be effected in methanol or water, in the open air, using Pd(OAc)(2) as a catalyst in the presence of K(2)CO(3). A variety of functional groups are tolerated. 相似文献
12.
WANG Min YANG Liang-Ru ZHANG Jin-Li ZHAO Liang SONG Mao-Ping WU Yang-Jie 《有机化学》2003,23(Z1):389-389
Transition-metal catalyzed reaction represents an extremely versatile method in organic synthesis. [1] Searching for highly efficient catalysts has been the aim of organic chemists. Palladium catalyzed coupling of aryl halides with arylboronic acids, Suzuki reaction, is one of the most powerful methods for carbon-carbon bond formation. [2] Here we report the high efficiency of cyclopalladated ferrocenylimine 1 for the Suzuki coupling reaction of aryl iodides with phenylboronic acid. Excellent yields and high turnover numbers were obtained under optimized conditions after repeated uses (Schemes 1, 2). 相似文献
13.
14.
A variety of heterobiaryl compounds have been synthesized by the Suzuki‐Miyaura coupling reactions of heteroaryl halides with potassium aryltrifluoroborates. Pd (OAc)2 was found to be highly efficient for the Suzuki‐Miyaura coupling reactions of various heteroaryl halides with potassium aryltrifluoroborates in aqueous systems, delivering the corresponding heterobiaryl compounds in good to excellent yields. 相似文献
15.
An approach to the macrocyclic core of phomactin A is described. Central to this strategy is the use of a cis-fused oxadecalin intermediate, prepared using the dihydropyrone Diels-Alder reaction. The conformational bias inherent to this system is then used to facilitate macrocycle formation via an intramolecular B-alkyl Suzuki coupling. 相似文献
16.
孙健 王加升 冯秀娟 Yoshinori Yamamoto Abdulrahman I. Almansour Natarajan Arumugam Raju Suresh Kumar 包明 《催化学报》2018,39(7):1258-1262
CO2是廉价的C1源,同时具有无毒、储量丰富的优点, 符合绿色化学发展要求. 利用 CO2构筑新的 C–C 键是化学固定CO2的重要方法. Β,γ-不饱和酯类结构单元是许多生物活性分子的重要组成部分, 经由双π-烯丙基钯中间体与 CO2反应, 合成新的β,γ-不饱和酯类化合物, 具有重要意义. CO2与有机硼化合物的羧化反应已有报道, 有机硼化合物具有低毒、对水不敏感等优点. 但是已报道的羧化 Suzuki 偶联反应存在诸多缺点: (1) 需要使用含膦或者氮杂环卡宾配体的催化剂, 而这些催化剂的制备过程使前期实验步骤变得冗长, 同时反应液的酸化后处理过程也会造成环境污染; (2) 有机硼试剂的官能团兼容范围窄, 限制了底物范围的拓展. 本课题组以原位生成的纳米钯粒子为催化剂, 在 CO2存在的温和条件下, 高效实现了苄氯与烯丙基硼酸频哪醇酯的羧化 Suzuki 偶联反应. 反应过程中无其它配体加入, 反应结束后不需要酸化或酯化的后处理过程. 该反应将具有广泛的官能团兼容性.本文以 TBAB 稳定的纳米钯粒子为催化剂, 在温和条件下, 实现了氯甲基芳香化合物、烯丙基硼酸频哪醇酯和 CO2的三组分羧化 Suzuki 偶联反应. 最佳反应条件为: Pd(acac)2(5 mol%)、TBAB (0.7 mmol, 1.4 equiv.)、KF (1 mmol, 2.0 equiv.)、苄基卤代物 (0.5 mmol)、烯丙基硼酸频哪醇酯 (0.6 mmol, 1.2 equiv.)、CO2(2.0 Mpa)、溶剂 THF (5 mL), 50 oC 反应 24 h. 在最佳反应条件下, 苯环、萘环以及杂芳环的氯甲基化合物均可发生该羧化反应. 苯环上取代基的位置对产物的收率有影响. 当使用 1-溴甲基萘作为底物时反应也能够发生, 收率与 1-氯甲基萘作为底物时的收率相当. 与已报道有机硼试剂的羧化反应相比, 该反应体系无需加入配体, 原位生成了纳米钯粒子, 避免了催化剂或者配体的复杂制备过程. 该反应中, 氟离子的存在是必要的, 对烯丙基硼酸频哪醇酯具有活化作用. 相似文献
17.
The cross‐coupling reaction between phenylboronic acid and various types of aryl halides (Suzuki reaction) was carried out using a catalytic amount of a new phosphine‐based catalyst under microwave irradiation. The reaction conditions were optimized and results showed that, by application of this catalytic system, N‐methyl‐2‐pyrrolidone as the solvent and potassium carbonate as the base, reactions could be completed in a short reaction time with high to excellent yields. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
The heme peroxidase-catalyzed iodination of human angiotensins I and II is described. It is observed that lactoperoxidase (LPO) can effectively and selectively iodinate the tyrosyl residues in angiotensin peptides. The thiourea/thiouracil-based peroxidase inhibitors effectively inhibit the iodination reactions, indicating that iodination is an enzymatic reaction and the mechanism of iodination is similar to that of peroxidase-catalyzed iodination of thyroglobulin. This study also shows that the monoiodo Ang I is a better substrate for the angiotensin converting enzyme than the native peptide. 相似文献
19.
20.
Sangita Karanjit Masaya Kashihara Atsushi Nakayama Lok Kumar Shrestha Katsuhiko Ariga Kosuke Namba 《Tetrahedron》2018,74(9):948-954
A palladium(0) nanocluster supported on hydrotalcite has been prepared and tested for the Suzuki coupling reaction. The prepared catalyst showed very efficient catalytic activity for cross coupling of iodo- and bromoarenes under very mild reaction conditions, affording >90% yield. Under the optimized reaction conditions, chloroarenenes also showed very good reactivity. Transmission electron microscopic imaging data showed the formation of very small Pd(0)-nanoclusters (d = 2.2 ± 0.5 nm) well dispersed on the support, which enhanced the activity and stability of the catalyst for the Suzuki cross-coupling reaction. This catalytic system offers an easy method of preparation with good activity and reusability up to five cycles. 相似文献