Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

Abstract

O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrenes were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained.

Ionic liquid coated sulfonated carbon/silica composites: novel heterogeneous catalysts for organic syntheses in water

“…Michael reaction of indoles to a,b-unsaturated carbonyl compounds provides easy access to 3-substituted indoles, which are important building blocks for the synthesis of important biologically active compounds and natural products. [37][38][39] Recently, catalysts such as polyvinyl sulfonic acid, 40 metal halide hydrates, 41 task-specic ionic liquids, 42 bimetallic iron-palladium catalysts, 43a and iron salts 43b have been reported for the Michael addition of indole to a,bunsaturated ketones. However, the acid-catalyzed conjugate addition of indoles requires careful control of acidity to prevent side reactions such as dimerization or polymerization.…”

One pot domino reaction accessing γ-nitroesters: synthesis of GABA derivatives

“…Among them, we can consider the use of molecular hydrogen in the presence of nickel Raney, 68 ammonium formate as a hydrogen source in the presence of Pd/C, 69 direct reduction with the NaBH 4 /NiCl 2 Á6H 2 O system, 70,71 Zn in acidic media, 72 and LiAlH 4 as a reducing agent. 74 In contrast, this methodology was not effective for the reduction of the g-nitroester synthesized in this work. 74 In contrast, this methodology was not effective for the reduction of the g-nitroester synthesized in this work.…”

“…73 The ammonium formate/Pd/C system had already been adopted in our research group to gain access to aminoindolines with simplicity and high yields. 74 In contrast, this methodology was not effective for the reduction of the g-nitroester synthesized in this work. Alternatively, the use of the NaBH 4 /NiCl 2 Á 6H 2 O system to reduce g-nitroesters 4a,d, according to procedures described in the literature (Scheme 6) was tested.…”

Eco-friendly methoximation of aromatic aldehydes and ketones using MnCl 2 .4H 2 O as an easily accessible and efficient catalyst

“…MnCl 2 .4H 2 O is also a GRAS substance [43], suitable for use in protic solvents. This mild and moisture compatible Lewis acid has been found to promote a handful of relevant transformations, such as mesylate to chloride conversion [44], esterification and transesterification reactions [45,46], Michael addition [47], glucose to fructose isomerization [48], condensation of carbonyls with amine derivatives [49], carbonyl reduction [50] and the reductive amination of ketones [51]. The salt has also been employed as a catalyst for cross couplings leading to C-X (X=N, S) [52,53] or C-C bond formation [54,55], and in C-H activation reactions resulting in further C-C bond formation [56][57][58][59].…”