Search

Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and nitrobenzene have been successfully carried out using activated hematite (α-Fe 2 O 3 ) as a new, heterogeneous and green catalyst. Sonication of neat α-Fe 2 O 3 in a water bath under air atmosphere at room temperature followed by heating at 200 °C, dramatically increase the activity of α-Fe 2 O 3 . With the catalyst loading as low as 5.0 mol%, a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high-yielding acylation reaction. It was found that the activated α-Fe 2 O 3 could be efficiently recycled and reused several times by simple washing with ethyl acetate, this cannot be attained with most of the traditional catalysts.

An efficient, regioselective, one-pot and two-step synthesis of β-hydroxy 1,4-disubstituted 1,2,3-triazoles from a wide range of non-activated terminal alkynes and epoxides and sodium azide by way of a three-component click reaction using a catalytic amount of [meso-tetrakis(o-chlorophenyl)porphyrinato]copper(II) (5 mol%) in excellent isolated yields is described. The reactions were performed in water as a green solvent at ambient temperature without any additives. By performing two reaction steps in one pot and purifying only at the final step, this procedure excludes any interim purification of in situ generated organic azide intermediates, which significantly improves the overall yield and reduces the reaction time. To benefit from the recovery and reuse of the catalyst, a new heterogeneous catalyst was prepared by simple and successful impregnation of the catalyst onto activated multi-walled carbon nanotubes (AMWCNT). The heterogeneous catalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic forced microscopy (AFM), and thermogravimetric (TG) analysis to estimate the amount of nitrogen adsorption, and Raman and FT-IR spectroscopy. Leaching experiments after ten successive cycles showed that the catalyst is most strongly anchored to the AMWCNT support. Mechanistically, porphyrinatocopper catalyzes each step of the reaction in different ways as a bifunctional catalyst including epoxide ring opening by azide delivery to epoxide, forming in situ generated 2-azido alcohols followed by activation of the C≡C triple bond of the starting terminal alkynes by forming a porphyrinatocopper-acetylide intermediate and thereby promoting the [3+2]-cycloaddition reaction as the key step to form the triazole framework.

A one-pot procedure for synthesis of 1,2,3-triazole derivatives via the three-component coupling (TCC) reaction between terminal alkynes, benzyl or alkyl halides, and sodium azide in the presences of 1 mol% nanoparticles copper/carbon (Cu/C) catalyst has been developed. The catalyst showed high catalytic activity and 1,4-regioselectivity for the [3+2] Huisgen cycloaddition in water as a “green” solvent and good to excellent yields were obtained in all cases. This procedure eliminates the need to handle organic azides, and they are generated in situ. The reaction has a broad scope and is especially practical for the synthesis of new azacrown ether and anthraquinone derivatives of triazole. The heterogeneous catalysts were fully characterized by scanning electron microscopy (SEM), atomic forced microscopy (AFM), X-ray diffraction (XRD), inductively coupled plasma (ICP) analysis and FT-IR experimental techniques. The catalyst was recycled ten times without significant loss of activity.