Conjugate addition of indoles and thiols with electron-deficient olefins catalyzed by Bi(OTf)3

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].…”

An efficient synthesis of 3-diethoxyphosphoryl-4-(1H-indol-3-yl)-3,4-dihydrocoumarins: a convenient approach to 3-methylene-4-(indol-3-yl)-3,4-dihydrocoumarins

“…Among several reactions of indole, the reactions involving C-3 functionalization of indole with electron-deficient olefins have attracted and continue to attract interest from the synthetic community. While the reaction of indoles with highly electrophilic nitroolefins and enones to furnish β-(indol-3-yl) alkylated products has been widely investigated, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] analogous reactions involving α,β-unsaturated esters to form 3-(indol-3-yl) alkanoates are rare. To date, two general strategies for the non-enantioselective synthesis of 3-(indol-3-yl) alkanoates have been reported.…”

Indium(III) chloride – catalyzed Michael addition of thiols to chalcones : A remarkable solvent effect

“…This addition to chalcone derivatives is very interesting and challenging as it is less facile compared to the addition to aliphatic acyclic enones and thus it is not always satisfactory with the conventional reagents used for general 1,4-addition. Recently, a number of procedures involving a variety of catalysts such as synthetic diphosphate Na 2 CaP 2 O 7 …”