Catalysis of the specific michael addition : The example of acrylate acceptors

Ordered organo-inorganic hybrid mesoporous solid acid catalysts (Zr–TMS–TFA) for Michael addition of indoles with α,β-unsaturated carbonyl compounds under environmentally benign solvent free conditions

“…The Michael addition of a,b-unsaturated carbonyl compound to indoles has been attempted using various Lewis acids such as FeCl 3 , LiCl, HgCl 2 [24,25], lanthanide salts (Ln = La, Sm, Yb) [26][27][28], InCl 3 and InBr 3 [29][30][31], Pd [32], CeCl 3 [33] , Bi(NO 3 ) 3 [34,35], Bi(OTf) 3 [36,37], Sc(DS) 3 [38], copper salts [39], and acidic clays [40]. The acid catalyzed reaction of indoles requires careful control of the acidity to prevent unwanted side reactions, such as dimerization and polymerization [41,42].…”

Clay (Montmorillonite K10) Catalysis of the Michael Addition of α,β-Unsaturated Carbonyl Compounds to Indoles: The Beneficial Role of Alcohols

“…When K10 alone is employed, this acid catalyst can interact with the Michael acceptor. This point has been addressed by Cabral et al [10]. Moreover, in the case studied here, we have to take into account that indole is partially protonated [12] by the clay acid sites, which is detrimental for the reaction from the kinetic point of view.…”

“…We also investigated the behaviour of K10 clays doped with AlCl 3 , FeCl 3 , and ZnCl 2 . The preparation of these catalysts has been reported previously [9,10].…”

Iron Catalysis in Synthetic Chemistry

“…A number of homogeneous, as well as heterogeneous, iron-catalyzed Michael addition reactions have enriched this field with prospects for the future. In 1989, Laszlo et al (62) reported an FeCl 3 catalyzed Michael addition of amines onto acrylate acceptors (Table XIII). Herein, FeCl 3 acted as a Lewis acid, which coordinated with the carbonyl oxygen of the acrylate acceptor and catalyzed the reaction toward a thermodynamically favored 1,4-addition.…”