Enlace-Connector View larger. Enlace-Connector · Display all pictures. Enlace Acetal Tubo polietileno Ø 16 mm. Reference: wm Condition: New. Al convertir el grupo hidroxilo anomérico en una función éter (hemiacetal On acetal) evita La única diferencia en sus estructuras, la estereoquímica del enlace. Acetal (VAN) Nombres de marca, Acetal (VAN) Analogos Acetal (VAN) RX enlace Acetal (VAN) MSDS (hoja de seguridad de materiales). Acetal_(VAN).
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Enlace Acetal Tubo polietileno Ø 16 mm
Microwave-assisted synthesis of Nitroketene N,S -Arylaminoacetals. In this paper we report the use of microwaves as heat source to promote the synthesis of a series of nitroketene N,S -acetals with good to excellent isolated yields.
These compounds are very useful intermediates for synthesizing nitrogen-containing heterocycles.
Nitroketene N,S -acetals are very useful intermediates for synthesizing nitrogen-containing aceetal, such as 2-aminonitro-4 H -chromenes, 1 4-imino-3,4-dihydropyrimidin-2 1 H -ones, 2 and quinoxalines.
The synthesis of nitroketene N,S -acetals 3 are usually performed by reaction of l,l-bis methylthio nitroethene 1 with one equivalent of several primary or secondary amines Scheme 1.
Nowadays, it is noteworthy to connect research in chemistry and environmental protection. One of the principles of green chemistry is energy efficiency, thus the synthetic methods should be conducted whenever possible at room temperature and pressure, to reduce the energy spent during a chemical process.
ACETAL – Definition and synonyms of acetal in the Spanish dictionary
One option is to replace the conventional heating by alternative energy sources such as microwave. Microwave-assisted organic synthesis has had a profound impact on the way that chemists approach organic and parallel synthesis.
Clearly, reductions in reaction times, improved yields and suppression of side products, relative to conventional thermal heating, are some benefits of this emerging technology. In a ongoing program towards the synthesis of quinoxalines, we investigated the reaction of nitroethene 1 with aniline using ethanol as solvent and microwave MW irradiation Scheme 1. We then performed a series of experiments in order to optimize this result, which are summarized in Table 1.
We observed that the rate of conversion of reagents increased with temperature and power of microwave entries 1 and 2 ; however when the temperature increased up to o C acegal power to W, by-products were formed entry 3. Thus, we acetzl to investigate the time reaction caetal keeping temperature at o C and power at 70 W entries 4, 5 and 6. We confirmed the optimization with p -methoxyaniline, emlace furnished higher yields in the same conditions.
After optimizing the reaction, we performed the coupling of different amines possessing electron donating and electron withdrawing groups to evaluate the scope of this protocol. Good to excellent isolated yields were obtained in most cases, excepting the reaction with anilines 2k and 2nprobably due to the presence of the strong electron withdrawing group. We have also observed that groups in the 2-position may cause steric hindrance effect, as for example for anilines 2d and 2g Table 2.
Due to the failure of the methodology as a result of the presence of strongly electron-withdrawing groups, we performed further tests with the 4-trifluoromethylaniline Table 3.
Therefore, we attempt the same procedure by using higher power and temperature entry 2. We have also tested different solvents entries 3 and 4. In general a reaction medium with a high loss tangent tan d at the standard operating frequency of a microwave synthesis reactor 2.
The spectroscopic data were identical with those described in the literature. In summary, we have demonstrated that reactions between amines and l,l-bis methylthio nitroethene 1 employing microwave heating is an advantage method since desired products can be obtained in good yields and shorter reaction time when compared to the conventional heating.
This protocol afforded a series of nitroketene N,S -acetals 3 in with good to excellent yields. acrtal
Unless otherwise noted, all commercially available reagents were purchased from Aldrich Chemical Co. Analytical thin-layer chromatography was performed on a 0. Flash column chromatography was performed using silica gel Kieselgel 60, mesh, E. The nitroketene N,S -acetals 3 were purified by flash chromatography employing hexanes: N-[1- Methylthio nitroethenyl]-1,3-benzodioxolamine 3l N-[1- Methylthio nitroethenyl]-benzenamine 3m 3,4,9, N-[1- Methylthio nitroethenyl]-cyclohexanamine 5 Supplementary information is available free of charge at http: I Nova26 Nova25 September 11, Web Release Date: All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License.
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Hemiacetal – Wikipedia
Introduction Nitroketene N,S -acetals are very useful intermediates for synthesizing nitrogen-containing heterocycles, such as 2-aminonitro-4 H -chromenes, 1 4-imino-3,4-dihydropyrimidin-2 1 H -ones, 2 and quinoxalines. Results and Discussion In a ongoing program towards the synthesis of quinoxalines, we investigated the reaction of nitroethene 1 with aniline using ethanol as enlaec and microwave MW irradiation Scheme 1.
Experimental Unless otherwise noted, all commercially available reagents were purchased from Aldrich Chemical Co.
Supplementary Information Supplementary information is available free of charge at http: How to cite this article.