The efficient and very simple conjugate addition of aromatic and aliphatic amines to a,b-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of silicon tetrachloride is reported. The reaction of aryl and alkyl amines with different Michael acceptors gave the corresponding Michael adducts with simple catalyst and good to excellent yields.The aza-Michael addition reaction is one of the most important methodologies in synthetic organic chemistry for preparation of b-aminocarbonyl compounds, which not only constitute components of biologically important natural products but also serve as key intermediates for the synthesis of b-amino alcohols, antibiotics, b-amino acids, chiral auxiliaries, and other nitrogen-containing compounds. 1,2The Mannich reaction is a classical method for the synthesis of b-amino carbonyl compounds. However, the reaction has disadvantages such as harsh reaction conditions, long reaction times, and a relatively narrow scope of substrates. 3 The aza-Michael addition of nitrogen nucleophiles including amides, carbamates, sulfonamides, and amines to electron-deficient alkenes in the presence of strong base or acid catalyst has attracted considerable attention as an alternative route for the synthesis of b-amino carbonyl compounds. 4 Since some functional groups may be susceptible to strong acid or base, a variety of catalysts 5 and promoters for aliphatic amines 6 have been introduced over the past few years.However, there are still some limitations with the existing methods; for example, the range of amine nucleophiles and Michael acceptors well suited to both catalytic and stoichiometric methodologies is generally restricted to simple aliphatic amines and Michael acceptors and there have been few reports involving simple catalysts or reagents to effect these transformations. 7 Thus, development of an efficient catalytic protocol that could overcome the above-mentioned disadvantages and facilitate the addition of both aromatic/aliphatic amines to a,bunsaturated compounds remains a challenge.As a part of our research aimed at developing green chemistry by using water as the reaction medium or by performing organic transformations under solvent-free conditions, 8 we describe herein a simple, highly efficient, and eco-friendly method for the synthesis of b-amino carbonyl compounds from aromatic and aliphatic amines and a,b-unsaturated Michael acceptors under solvent-free conditions.In order to find the best reaction conditions, we first studied the reaction of aniline and methyl acrylate with different loadings of starting materials and catalyst. It was found that the reaction of methyl acrylate (1.04 equiv) and aniline (1 equiv) in the presence of commercially available silicon tetrachloride (2 mol%) under solvent-free conditions proceeded smoothly within four hours to afford the conjugate addition product exclusively and in quantitative yield. Furthermore, in organic solvents, such as CH 2 Cl 2 , MeCN, toluene, ethanol, water, and tetrahydrofuran the M...
In this report, we describe new conditions for the formation of copper gels and aerogels via epoxide addition to CuBr 2 in dimethylformamide (DMF). These CuBr 2 -derived sols undergo a rapid gel transition and result in materials that have enhanced mechanical properties when compared with the gels derived from CuCl 2 . Additionally, upon air-annealing, they convert to nanoscopic CuO at temperatures much lower than the CuCl 2 analogues. Moreover, annealing under nitrogen results in copper species with reduced oxidization states including Cu 2 O and metallic Cu. The ratio of copper oxidation states can be controlled by simple modification of the thermal program used to anneal the materials. The thermal reduction of the copper is attributed to retained DMF ligands in the as-prepared aerogels which was confirmed by FTIR spectroscopy. These aerogel materials were characterized by powder X-ray diffraction (PXRD), physisorption, thermogravimetric analysis (TGA), and temperature programmed reduction (TPR).
Persulfates such as peroxydisulfate (PDS) are among the most widely applied oxidants for breaking down organic contaminants in water. The oxidation power arises from conversion of persulfate to sulfate radical or other reactive oxidants. Ferrite materials are good candidates for catalytic activation of persulfate owing to its ability to incorporate a variety of transition metals in the structure, stability against aqueous dissolution, and magnetic susceptibility allowing catalyst separation and reuse. In this study, ferrite spinels incorporating zinc, nickel, cobalt, or copper were synthesized with an epoxide-driven sol–gel method and were annealed at 350 and 700 °C, respectively. The particles were evaluated for activating PDS using phenol as a model organic contaminant. Cu-ferrite annealed at the low temperature (350 °C) was identified to be the most active ferrite for PDS activation. This solid consists of predominantly CuFe2O4, while at the higher annealing temperature, decomposition of CuFe2O4 to Fe2O3 and CuO and significant increase in particle size resulted in severe loss of PDS activation ability. Remarkable increases in phenol oxidation rate were observed above pH 9.0 and were attributed to PDS activation by phenoxide. The presence of methanol, bicarbonate, or chloride ion (1–5 mM) significantly slowed down phenol oxidation, whereas the addition of tert-butyl alcohol did not affect the degradation rate, indicating the dominant oxidant is sulfate radical. Comparison of Cu-ferrite against reference metal oxides suggests that the catalytic performance of Cu(II) sites in the ferrite phase is comparable to those in the highly active but leachable CuO, and Cu-ferrite demonstrated good reusability during repeated phenol oxidation experiments.
Ferrite spinels of the late first-row d-block metals were synthesized in a uniform manner via the epoxide addition method.
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