排序方式: 共有515条查询结果,搜索用时 15 毫秒
31.
Xiu-Jiang Du Zhi-Peng WangYan-Ling Hou Cheng ZhangZheng-Ming Li Wei-Guang Zhao 《Tetrahedron letters》2014
A new method has been developed for the Michael addition of nitrogen- and carbon-containing nucleophiles to cyclic enones. Using this conjugate addition reaction, a variety of different nucleophiles can react with a range of cyclic enones in the presence of p-toluenesulfonic acid under solvent-free ultrasound irradiation conditions affording the corresponding C–N or C–C adducts in good to excellent yields. Comparatively, performing the reaction under ultrasound irradiation gives higher yields, is more efficient and environmentally benign than performing it at high pressure. 相似文献
32.
Three new metal phosphites, formulated as (H3O)2·Mn2(HPO3)3 (1), Co(bpy) (H2O) (HPO3) (2), and H2tmpda·Zn3(HPO3)4 (3), have been synthesized under solvent-free conditions, where bpy = 4,4′-bipyridine, and tmpda = N,N,N′,N′-tetramethyl-1,3-propanediamine. Compound 1 has a double-layered structure with a thickness of 5.68 Å. Compound 2 has an inorganic-organic hybrid framework with cobalt phosphite layers pillared by bpy ligands. Compound 3 has a three-dimensional open-framework structure containing 8-ring channels. The temperature dependence of the magnetic susceptibility of compounds 1 and 2 were also investigated. 相似文献
33.
An efficient synthesis of Biginelli-type compounds using potassium phthalimide as a green, mild, and commercially available organocatalyst in a one-pot, multi-component cyclocondensation reaction of cyclopentanone, aldehydes, and urea/thiourea is reported. The present methodology is a green approach to access 4-aryl-7-(aryImethylene)-3,4,6,7-tetrahydro-1H-cyclopenta[d]pyrimidin-2(5H)-ones/thiones. It offers several merits such as simple operational procedures, no use of hazardous organic solvents, and cheap and environmentally friendly solid basic catalyst. 相似文献
34.
Ceric ammonium nitrate (CAN) supported HY-zeolite has been used as an efficient catalyst for the one- pot synthesis of 1,8-dioxo-octahydroxanthenes from the readily available 1,3-diketone and aromatic aldehydes under solvent-free conditions. The present methodology is cost-effective in addition to other advantages like high yields of products in shorter reaction time and simple workup procedure without the use of any injurious solvents. 相似文献
35.
In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHS) is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity. 相似文献
36.
Nader Ghaffari Khaligh 《催化学报》2014,35(7):1036-1042
3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free,and reusable Brnsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl- hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity. 相似文献
37.
The Keplerate‐type giant nanoporous isopolyoxomolybdate (NH4)42[MoVI72MoV60O372‐(CH3COO)30(H2O)72], denoted {Mo132}, has been used as a catalyst for the synthesis of1,2,4,5‐tetrasubstituted imidazoles by the one‐pot, four‐component thermal reaction of benzil with aromatic aldehydes, primary amines, and ammonium acetate under solvent‐free conditions. The catalyst was prepared according to a previously published literature procedure using inexpensive and readily available starting materials, and subsequently characterized by FT‐IR, UV and X‐ray diffraction spectroscopy, as well as microanalysis. The results showed that {Mo132} exhibited high catalytic activity towards the synthesis of 1,2,4,5‐tetrasubstituted imidazoles, with the desired products being formed in good to high yields. Furthermore, the catalyst was recyclable and could be reused at least three times without any discernible loss in its catalytic activity. Overall, this new catalytic method for the synthesis of 1,2,4,5‐tetrasubstituted imidazoles provides rapid access to the desired compounds following a simple work‐up procedure, and avoids the use of harmful organic solvents. This method therefore represents a significant improvement over the methods currently available for the synthesis of tetrasubstituted imidazoles. 相似文献
38.
Nader Ghaffari Khaligh 《催化学报》2014,35(9):1497-1503
1,1''-Butylenebispyridinium hydrogen sulfate is an efficient, halogen-free and reusable Brönsted ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl-hexahydro-trimehtyl-5- oxoquinoline-3-carboxylates by the one-pot condensation of dimedone, aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantages of high yield, clean reaction, simple methodology, and short reaction time. The ionic liquid can be recycled five times without significant loss of the catalytic activity. 相似文献
39.
A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis. 相似文献
40.
A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and N2 adsorption-desorption measurements.The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols,phenols,and amines under solvent-free conditions.Under optimized conditions,efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained.Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature,while the reaction time was longer for the acetylation of alcohols and phenols,showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups.The catalyst can be reused without obvious loss of catalytic activity.The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4.The method gives high yields,and is clean,cost effective,compatible with substrates having other functional groups and it is suitable for practical organic synthesis. 相似文献