Advances in liquid-phase Friedel-Crafts acylation of aromatics catalyzed by heterogeneous solids

Abstract

In the last few decades, significant improvements toward the development of environmentally benign processes have been achieved in the liquid-phase Friedel-Crafts acylation reactions. Many efforts have been devoted to the research on solid catalysts adequate to substitute homogeneous protonic acids or Lewis acids as traditionally employed catalysts in the acid-catalyzed FriedelCrafts acylation processes. This short article describes the recent developments on catalysis by gallium (Ga), indium (In) and thallium (Tl) based novel heterogeneous solids for the liquid-phase Friedel-Crafts acylation of aromatics by acyl halide. The above heterogeneous catalysts are efficient for Friedel-Crafts acylation reaction and exhibited superior activity than the traditionally employed strongly acidic solid catalysts. Unlike conventional acidic catalyst, the acylation activity of Ga, In and Tl based solids, additionally having redox functions, does not depend solely on their acidic properties, even present. These solids in their non-acidic or basic form also show high acylation activity. Based on the catalytic results over these novel solids a plausible reaction mechanism for the acylation is proposed.

Guanidinium vs. Ammonium Surfactants in Soft‐Templating Approaches: Nanostructured Silica and Zwitterionic i‐Silica from Complementary Precursor–Surfactant Ion Pairs

“…Finally, hysteresis loops indicate bottle-neck shapes of the pores. As in the case of materials obtained in the presence of ammonium surfactants, [5,49] the pore-size distribution plots of the materials B, C and D (Figure 3) indicate that the length of the alkyl chain of the surfactant determines the average pore diameters of the formed materials. The smallest pores are observed in material A, obtained in the presence of decylguanidinium chloride (DGC), whereas the largest pores are found in material D, synthesised in the presence of cetylguanidinium chloride (CGC).…”

“…In contrast, the diffractogram of the MCM-41 material clearly shows the (100), (110) and (200) diffraction peaks, charac- teristic for materials with a highly ordered 2D hexagonal architecture. [49] From the position of the (100) diffraction peak, the d-spacing in this material can be calculated to be 41.5 Å. The isotherm of the MCM-41 sample shows a typical type IV isotherm with a sharp adsorption step at relative pressures of p/p 0 = 0.3-0.4 and a plateau up to the satura-tion pressure, indicating a narrow pore-size distribution and an average pore diameter of 27 Å.…”

Regioselective Friedel–Crafts Acylation Reaction Using Single Crystalline and Ultrathin Nanosheet Assembly of Scrutinyite-SnO2

“… 81 Therefore, along with the conventional acid-catalyzed mechanism for FC acylation, a redox mechanism also can be expected. 82 , 83 The steps involved in this pathway are mentioned below: …”

“…Again, the reduction of Sn 4+ to Sn 2+ is relatively easy owing to the positive standard reduction potential for Sn 4+ (aq) + 2e – → Sn 2+ (aq) ( E ° Sn 4+ /Sn 2+ = +0.13 V) . Therefore, along with the conventional acid-catalyzed mechanism for FC acylation, a redox mechanism also can be expected. , The steps involved in this pathway are mentioned below: …”

Acylations with Long-Chain Acid Anhydrides and Acyl Chlorides over Zeolite Beta

“…Several papers and reviews [10][11][12][13], in which zeolites were successfully used for production of important intermediates or products of fine chemicals by acylation were published. Acylation of anisole [14][15][16][17], veratrole [18,19], naphthalene [20,21], 2-methoxynaphthalene [22][23][24], toluene [25,26], isobutylbenzene [27], phenol [28,29] or heterocycles [30,31] belong among very important acylation reaction catalyzed with zeolite catalysts.…”