Synthesis of symmetrical and unsymmetrical 3,3-di(indolyl)indolin-2-ones under controlled catalysis of ionic liquids

Abstract

a b s t r a c t Three ionic liquids, [BMIM][BF 4 ] doped with 60 mol % of LiCl ([BMIM][BF 4 ]-LiCl), N,N,N,N-tetramethylguanidinium trifluoroacetate (TMGT), and N,N,N,N-tetramethylguanidinium triflate (TMGT f ) were found useful as catalyst solvents for controlled 3-indolylation of isatins. Our investigation revealed that the reaction between isatin and indoles in [BMIM] [BF 4 ]-LiCl or TMGT f media stops at the step of addition of the two components providing 3-indolyl-3-hydroxyindolin-2-ones while the ionic liquid TMGT runs the reaction further through accompanying Friedel-Crafts substitution to afford symmetrical 3,3-di(indol-3-yl)indolin-2-ones. To take advantage of the difference between the effects of these ionic liquids on the reaction progress, we planned a two-step protocol for the efficient synthesis of unsymmetrical 3,3-di(indol-3-yl)indolin-2-ones.

MCM-41-Accelerated PWA Catalysis of Friedel-Crafts Reaction of Indoles and Isatins

“…However, product 3l, the yield of 5-methyl-3,3-di(indolyl) oxindole, was excellent ( (12)). Wherever -F and -Cl groups are located in indoles or isatins of aromatic rings, they all could be tolerated well and gave the desired product derivatives 3e-3h, 3m, and 3o in excellent yields ( Table 2, entries (5)- (8), (13), and (15)). However, the benzene ring of indoles or isatins bearing sterically demanding groups, such as -Br and -NO 2 , could only give corresponding products with lower yields, respectively ( Table 2, entries (9), (10), and (14)).…”

“…Some literature sources revealed that the synthesis of 3,3-diaryloxindole skeleton can be achieved by coupling of indoles and isatins with acid [9,10], I 2 [11], metal salts [12], ionic liquids [13], CAN [14], -CD [15], Amberlyst-15 [16], and nanomaterials [17]. Despite these important contributions, developing and searching for a highly effective catalytic system is still challenging.…”

β‐Cyclodextrin: A Green and Efficient Supramolecular Catalyst for Organic Transformations

“…Number of methods for the synthesis of 3‐substituted‐3‐hydroxyoxindoles and 3,3‐di(indolyl)indolin‐2‐ones have been reported in the literature involving the use of Silicotungstic acid (H 4 SiW 12 O 40 ), LiClO 4 , Sc/In(OTF), cupreine, ionic liquids, bismuth(III) triflate, silica sulfuric acid, ruthenium trichloride, ceric ammonium nitrate (CAN) under ultrasound irradiation, iodine, water‐ethanol, at reflux temperature and β‐cyclodextrin . A literature survey reveals that the earlier method reported required not only the use metal catalyst, acidic or basic condition, hazardous organic solvents but also involve long reaction times and tedious workup procedure.…”

Iron‐containing ionic liquid as an efficient and recyclable catalyst for the synthesis of C3‐substituted indole derivatives

“…isatin and 2 eq. indoles . Even though, these methods still suffered from various disadvantages such as high reaction temperature, large amounts of catalyst loading and limited substrate scope.…”