Acid catalyzes the synthesis of aromatic gem-dihalides from their corresponding aromatic aldehydes

Sulfated Zirconia-Catalyzed Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) Under Solventless Conditions: Competitive Multicomponent Biginelli vs. Hantzsch Reactions

“…Aside the fact that they have excellent activity and selectivity, even on industrial scales, and in most cases these substances can be recovered from reaction mixtures and reused with good results [4], these solid acids are important from an environmental point of view because they produce less hazardous by-products. In this context, solid sulfated zirconia [5] have been used, due to their acidic and shape-selective nature, for performing the synthesis of heterocycles [6,7], acylation of aromatics ketones [8] and stereocontrolled glycosidations [9], synthesis of aromatic gem-dihalides [10], acylation of crown ethers [11], and chemoselective synthesis of acylals from aromatic aldehydes and their deprotections [12]. It is also known that in many cases organic reactions under solvent free conditions occur more efficiently and more selectively than do their solutions counterparts [13].…”

Promoted Zirconia Solid Acid Catalysts for Organic Synthesis

“…These are also used as starting materials for several C-C coupling reactions and for the synthesis of imines as well as parent raw materials for the preparation of their corresponding amines, acids and alcohols [43]. Wolfson et al [12] investigated the synthesis of aromatic gemdihalides from their corresponding aromatic aldehydes by using various acid catalysts. They observed that AlCl 3 and SZ are the most active homogeneous and heterogeneous catalysts, respectively.…”

“…In recent times inorganic solid acid-catalyzed organic transformations are gaining more attention due to the proven advantage of heterogeneous catalysts, simplified product isolation, mild reaction conditions, high selectivity, ease in recovery and reuse of the catalysts, and reduction in the generation of wasteful byproducts [10][11][12]. In that connection we were interested in investigating various industrially important organic reactions aimed at replacing toxic and corrosive reagents, noxious or expensive solvents and multistep processes, with single-step solvent-free ones by using environmentally benign solid acid catalysts.…”

“…The resultant sulfated zirconium hydroxide is then calcined in air at 550-650°C to generate acidity. To impregnate molybdate (10)(11)(12)(13)(14)(15) wt.%) and tungstate (10-18 wt.%) promoters, the desired quantities of ammonium heptamolybdate or ammonium metatungstate precursors dissolved in doubly distilled water are normally employed [7,20]. The resultant molybdated and tungstated zirconium hydroxide samples are then calcined in air at 650-800°C in order to generate the acidity [20].…”

Heteropolyacid as an Efficient Catalyst for Synthesis of 3,4-Dihydro-1H-2,3-benzothiazine-2,2-dioxides

“…Heterogeneous catalysts are used in a great number of developed processes, and in view of the increasingly strict environmental legislation, the application of these catalysts has become attractive. [5][6][7][8] In addition, solid acid catalysts can be regenerated and reused after the reactions.…”