Gold-Catalyzed Conjugate Addition Type Reaction of Indoles with α,β-Enones

Abstract

3-Unsubstituted indoles undergo regioselective alkylation at the 3-position of the indole nucleus through gold-catalyzed conjugated addition type reaction with α,β-enones. 3-Substituted indoles undergo C-2 alkylation. Sequential C-3/C-2 gold catalyzed alkylation of the indole with dibenzylidene acetone gives a poly­cyclic indole b-annulated with a seven-membered cycle

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

“…[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.…”

Gold‐Catalysed Direct Couplings of Indoles and Pyrroles with 1,3‐Dicarbonyl Compounds

“…[6] By contrast, to the best of our knowledge there are only rare examples of coupling reaction of indoles with 1,3-dicarbonyl compounds [7] and the direct coupling of pyrroles with 1,3-dicarbonyls has not been previously reported. Our continuing interest in the development of catalytic processes that exploit selective and controllable C À H functionalisation of aromatic heterocycles [8] led us to develop new synthetic approaches for the direct intermolecular alkenylation [9] of indoles and pyrroles through their gold-catalysed reactions with 1,3-dicarbonyl compounds. Gold is an excellent catalyst for the C À H functionalisation of aromatic heterocycles, thereby opening new pathways for carbon-carbon bond formation.…”

Al-MCM-41 as a mild and ecofriendly catalyst for Michael addition of indole to α,β-unsaturated ketones

“…They are usually carried out in the presence of catalytic and stoichiometric amounts of Lewis acids. During the past few years, various catalysts [26][27][28] were used for the synthesis of 3-substituted indoles from ␣,␤-unsaturated carbonyl compounds including Lewis and Bronsted acid catalysts such as CuBr 2 [29], InBr 3 [3], [Al(DS) 3 ]·3H 2 O [30], Au(III) [31], CeCl 3 ·7H 2 O-NaI [2], SmI 3 [32,33] and K10-FeO [34]. Most of these reactions have been studied using highly nucleophilic indoles and yields are unsatisfactory.…”