A new approach for the synthesis of bisindoles through AgOTf as catalyst

Abstract

SummaryA novel approach for the catalyzed formation of bisindolylmethane derivatives (BIMs) is described. This methodology is the unique example where AgOTf has been successfully used for the activation of aldehydes, giving easy access to a broad range of bisindolyl derivatives with excellent results. Moreover, the simplicity and easy operational methodology using a small amount of commercially available AgOTf (1–3 mol %), one of the lowest catalytic charge used in this process to date, makes this procedure an alternative approach for this interesting and appealing reaction.

Tetranuclear Zn/4f coordination clusters as highly efficient catalysts for Friedel–Crafts alkylation

“…14 Various catalytic systems and metal salts have been reported for the synthesis of BIMS, however these methods suffer from a number of disadvantages such as expense; toxicity of reagents; high temperatures, high catalytic loading (stoichiometric-10%) and photosensitivity (silver salts). [15][16][17][18] In 3d/4f chemistry, 4f centres may be replaced by Y III or Gd III without altering the core topology, 19 therefore permitting 89 Y NMR 20 or EPR 21 for characterization of the solution species, as well as allowing study of the catalytic reaction in situ to gain mechanistic insights. Also, the possibility to alter the 3d centres while retaining the topology 22,23 may provide more insights regarding the reaction mechanism, due to the different coordination behaviour to substrates (heteroatoms N, O or s), anticipated to be seen when Co or Ni or Cu or Zn are used.…”

Simple iodoalkyne-based organocatalysts for the activation of carbonyl compounds

“…A plausible mechanism is proposed assuming the same route as that previously reported by us when using AgOTf as a Lewis acid (Scheme 2). 28 Hence, catalyst I would activate the first addition of one molecule of indole 2 to aldehyde 1 through halogen bonding (4). 31 Unstable intermediate 5 would promote the elimination of a molecule of H 2 O to give azafulvene derivative 6.…”

“…25 This family of indoles discloses a range of biological properties such as antibacterial, antifungal, antimicrobial, anti-inflammatory or antitumor, among others. 26 Inspired in our own experience in the field of organocatalysis 27 using hydrogen bond-based catalysts, we focused our attention on the activation of aldehydes for the production of bisindoles 28 using iodoalkyne derivatives (non-perfluorinated) as promising catalysts for the first time in the literature.…”

Enzymatic approach to cascade synthesis of bis(indolyl)methanes in pure water

“…7 Bis(indolyl)methanes are generally obtained from cascade reactions of indole with carbonyl compounds catalyzed by protic or Lewis acids, which may be easily captured by nitrogenous compounds so as to bring some problems for the synthesis of bis(indolyl)methanes. 8 Recently, various novel catalysts have been reported to synthesize bis(indolyl)methanes, such as aza-crown ether ionic liquids supported on magnetic Fe 3 O 4 @SiO 2 core-shell particles, 9 nanocomposites ZrO 2 -Al 2 O 3 -Fe 3 O 4 , 10 1-hexenesulphonic acid sodium salt under ultrasound irradiation, 11 SDS, 12 zeolite, 13 graphene oxide, 14 AgOTf, 15 LASSC catalytic system, 16 meglumine catalyst, 17 NADES, 18 etc. However, there are some shortcomings in the most of catalytic methods mentioned above including expensive or complicated catalyst used, relative high temperature and excessive substrate needed, volatile organic solvent employed, etc.…”