echemi logo
Product
  • Product
  • Supplier
  • Inquiry
    Home > Green chem.: the Prakash group of the University of Southern California reported the synthesis method of substituted 1,2,3-triazoles without solvent and metal participation

    Green chem.: the Prakash group of the University of Southern California reported the synthesis method of substituted 1,2,3-triazoles without solvent and metal participation

    • Last Update: 2018-08-12
    • Source: Internet
    • Author: User
    Search more information of high quality chemicals, good prices and reliable suppliers, visit www.echemi.com
    Nh-1,2,3-triazole is easy to bind to many receptors and enzymes in vivo, so it has a wide range of applications in pharmaceutical chemistry Many compounds containing nh-1,2,3-triazole have been proved to have many biological properties, such as antitumor, antifungal, antituberculous and antibacterial activities In 1893, Michael first found that 1,3-dipolar cycloaddition could occur between alkyne and azide to obtain 1,2,3-triazole compounds Woodward and Hoffmann classified these reactions as thermodynamic cycle processes Later, Sharpless et al classified it as click chemistry Subsequently, copper and ruthenium catalyzed azido alkyne cycloaddition reaction has made great progress, and has been widely used in supramolecular chemistry, catalysis, material science, pharmaceutical and many other fields However, in the field of biology and pharmacy, the use of trace metal catalysts may bring heavy metal residues and potential toxicity problems In addition, the toxicity and explosiveness of sodium azide also bring many safety problems in the practical application To solve this problem, chemists have developed ways to use nonmetallic and safer reagents to complete click reaction, such as using other nonmetallic additives, using high tension or electrophilic alkynes to speed up the reaction However, the method of 1,2,3-triazole synthesis, which can be amplified, non-metallic, safer and more economical, has yet to be developed (source: Green chem.) recently, the research team of Professor g K Surya Prakash of the University of Southern California developed a solvent-free and metal free synthesis method of substituted 1,2,3-triazoles In this method, microwave is used instead of traditional heating, which can reduce the occurrence of many side reactions and realize the amplification reaction Its green, economic, safe and biocompatible reaction conditions and simple and convenient post-treatment and purification provide a very attractive method for the synthesis of 1,2,3-triazoles Relevant research results were published in green chem (DOI: 10.1039/c8gc01516c) Firstly, the microwave reaction conditions were screened with Diphenylacetylene and TMSN 3 as substrates (Table 1) When 1.5 equivalent TMSN 3 and 1 equivalent diphenyl acetylene react at 200 ℃ and inert gas for 6 hours, 84% yield of target product 11 can be obtained, while only 28% yield can be obtained by traditional oil bath heating (source: Green chem.) the author recorded the temperature and pressure changes of the whole reaction process in a microwave reactor It can be seen from Figure 2 that when the temperature is heated to 200 ℃, the reaction pressure increases obviously; because the product has a lower vapor pressure than the reactant, the reaction pressure decreases gradually as the reaction proceeds (source: Green chem.) then, the author investigated the application scope of the reaction substrate (Table 2) The end alkynes such as phenylacetylene and CYCLOPROPYLENE can react with TMSN 3, which proves that this method is widely applicable to aromatic and aliphatic end alkynes In addition, symmetrical and asymmetric endoalkyne (9-16) are also suitable substrates It is found that the existence of the polar part plays a positive role in increasing the reaction rate because the polar molecules can selectively absorb microwave radiation rather than remain inert to them The alkynes containing TMS have larger steric hindrance, and β - Si effect makes alkynes more electron rich, so it is not conducive to 1,3-dipolar cycloaddition, and the reaction yield is relatively low (source: Green chem.) in addition, the majority of triazoles after separation were found to be 2 h tautomers by NMR Although the 1,3-cycloaddition reaction of alkyne with TMSN 3 will produce 1H isomer at the beginning, it will produce 2H isomer with more stable thermodynamics However, the NMR hydrogen and carbon spectra of compound 16 show that the molecule is asymmetric, indicating that compound 16 is a 1H isomer Moreover, in the temperature controlled NMR experiment, the author found that with the decrease of temperature, the methyl peak of product 16 gradually became sharper, and finally multiple peaks appeared at - 10 ℃ Even at 45 ℃, two independent trimethylsilane peaks can be observed, which reflects that the tautomerization of 16 requires a very high energy barrier DFT calculation shows that even though 2H tautomer B is more stable than a, the high activation energy (46.3 kcal / mol) of tautomerism hinders the tautomerization of B and a However, a more stable tautomer 16b can be obtained in acid medium by over activation of deprotonation - reprotonation loop The structure of compound 16 was confirmed by X-ray diffraction The bond angle analysis showed that the compound was 1H isomer (source: Green chem.) further, the author found that the methylation reaction of product 16 resulted in n-1 methylation product 17, but no n-2 methylation product was observed This shows the particularity of compound 16 (source: Green chem.) conclusion: the research team of Professor g K Surya Prakash of the University of Southern California has developed a solvent-free, metal free, microwave assisted method for the preparation of substituted 1,2,3-triazole compounds The characteristics of green, economy, safety and simplicity of purification make this method very attractive in practical applications.
    This article is an English version of an article which is originally in the Chinese language on echemi.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to service@echemi.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

    Contact Us

    The source of this page with content of products and services is from Internet, which doesn't represent ECHEMI's opinion. If you have any queries, please write to service@echemi.com. It will be replied within 5 days.

    Moreover, if you find any instances of plagiarism from the page, please send email to service@echemi.com with relevant evidence.