A natural phosphate and doped-catalyzed Michael addition of mercaptans to α,β-unsaturated carbonyl compounds

Perchloric Acid Impregnated on Silica Gel (HClO4/SiO2): A Versatile Catalyst for Michael Addition of Thiols to the Electron‐Deficient Alkenes

“…are in an anti orientation as shown in Figure 2. Moreover, by employing the present protocol, various α,β-unsaturated esters namely methyl acrylate (8), methyl methacrylate (9) and ethyl acrylate (10) furnished the desired Michael addition products 8b, 9b and 10b respectively, on reaction with thiophenol (B) in good yields. Furthermore, our methodology can be extended for 1,4-conjugate addition reaction of thiols with acrylonitrile (11) and acrylamide (12) under identical conditions.…”

“…[6a,7] Under heterogeneous conditions, various solid catalysts have been found to be useful. For example, natural phosphate or phosphate doped with potassium fluoride, [8] zeolite, [9] clay-supported NiBr 2 and FeCl 3 , [10] Fluoroapatite, [11] polymer-supported Nafion ® SAC-13 [12] and dodecatungstophosphoric acid (H 3 PW 12 O 40 ). [13] Moreover, a wide variety of Lewis acid catalyst and other reagents have been used over the years for the similar transformation.…”

High Surface Area MgO as a Highly Effective Heterogeneous Base Catalyst for Three-Component Synthesis of Tetrahydrobenzopyran and 3,4-Dihydropyrano[c]chromene Derivatives in Aqueous Media

“…In contrast to the extensive studies involving heterogeneous acid catalysts, fewer efforts have been made to develop heterogeneous base catalysts [16]. Several solid bases have been reported as being effective in this respect such as zeolites [17], alkali metals supported on alumina (Na/NaOH/cAl 2 O 3 ) [18], clay minerals [19], hydrotalcites (HDT) [20], metal oxides such as magnesium oxide (MgO) and mixed metal oxides, for example magnesium-lanthanum mixed oxide [21]. Amongst these solid bases, magnesium oxide (MgO) has recently been studied the most [11].…”

Green Michael addition of thiols to electron deficient alkenes using KF/alumina and recyclable solvent or solvent-free conditions

“…[5][6][7] In view of these aspects, there are a large number of reported methods for both basic and acidic promoted selective 1,4-additions, including heterogeneous [8][9][10][11][12][13][14][15][16] and homogeneous catalysis, [17][18][19] as well as asymmetric versions. 20,21 Thus, solid catalysts, such as basic anion-exchange resins, 8 natural 9 and synthetic phosphates, 10 montmorillonite clays, 11 solid potassium carbonate, 12 base 13 and acid supported on alumina 14 have been used to perform the 1,4-addition of thiols to a series of electron-poor alkenes. Besides, the use of non-volatile and non-toxic solvents, such as water, 22,23 ionic liquids, 18,19 and ethylene glycol 24 to perform the Michael addition was also described.…”

“…Besides, the use of non-volatile and non-toxic solvents, such as water, 22,23 ionic liquids, 18,19 and ethylene glycol 24 to perform the Michael addition was also described. However, the use of solid-supported catalysts in Michael addition to α,β-unsaturated aldehydes has been scarcely explored [8][9][10][11][12][13][14][15][16] and, to the best of our knowledge, the use of glycerin as a renewable and recyclable solvent for the Michael addition of thiols to electron-poor alkenes has not been described.…”