Simple but efficient synthesis of bis(indolyl)methanes by the condensation reaction of substituted benzaldehydes with indole over mesoporous ZrO2–MgO green catalysts under solvent free conditions

3‐Amino‐5‐mercapto‐1,2,4‐triazole‐functionalized Fe3O4 magnetic nanocomposite as a green and efficient catalyst for synthesis of bis(indolyl)methane derivatives

“…Finally, the nucleophilic attack of the second mole of indole to intermediate V and abstraction of a proton from intermediate VII result in the production of corresponding bis(indolyl)methane. The catalyst is reused in the next reaction cycle, and increases the electrophilicity of the carbonyl group with adsorbed hydrogen 30, 50 …”

“…Several products containing bis(indolyl)alkane derivatives have been separated previously from marine sources 28, 29 . In this regard, various methods have been reported for the synthesis of bis(indolyl)alkane derivatives, especially bis(indolyl)methanes, through electrophilic substitution of indole with carbonyl compounds in the presence of various acid or base catalytic reagents such as ZrO 2 –MgO, 30 tetrabutylammonium hydrogen sulfate, 31 montmorillonite K‐10, 32 zeolite, 33 ammonium chloride, 34 tungstophosphoric acid supported on zirconia, 35 Fe 3 O 4 @silica sulfuric acid, 36 H 5 PW 10 V 2 O 40 /pyridino‐Fe 3 O 4 , 37 nano‐Fe 3 O 4 , 38 ZrO 2 –Al 2 O 3 –Fe 3 O 4 , 39 and [{Ti(salophen)H 2 O} 2 O][OSO 2 C 8 F 17 ] 2 40 . Although these procedures are valuable, some of them have disadvantages.…”

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

“…The most common examples in literature for the reaction of the synthesis of BIMs under solvent-free conditions utilize either protic acids, such as camphorsulfonic acid (CSA) [44], diammonium hydrogen phosphate (DAHP) [45], Amberlyst 15 [46], P 2 O 5 /MeSO 3 H [47], p-sulfonic acid calix [4]arene [48], xanthan sulfuric acid (XSA) [49], H 5 PW 10 V 2 O 40 /pyridinosanta barbara amorphous-15 (SBA-15) [50], TiO 2 -SO 4 2− [51,52], humic acid [53] or Lewis acids, such as N-bromosuccinimide (NBS) [54], silica chloride [55], Ph 3 CCl [56], ZnO [57], La(NO 3 ) 3 •6H 2 O [58], V(HSO 4 ) 3 [59], Cu(ClO 4 ) 2 •6H 2 O [60], Fe/Al pillared clay [61], trimethylsilyl chloride (TMSCl) [62], BiCl 3 -loaded montmorillonite K10 [63][64][65][66][67], ZrO 2 -MgO [68] or CaO [69]. Silica gel is an intriguing solid support, since it is a low cost, commercially available and non-hazardous support, that can be employed in tandem with various traditional catalysts [70].…”

Synthesis, characterization, and antibacterial activity of novel bis(indolyl)methanes sourced from biorenewable furfurals using gluconic acid aqueous solution (GAAS) as a sustainable catalyst

“…12,13 In this regard, bis(indolyl)methane (BIM) is a welldocumented class of heterocycle with remarkable antimicrobial, antibacterial, antiviral, antifungal, anti-metastatic, analgesic, and anti-inammatory activities. [14][15][16] BIMs are synthesized by the acid-catalyzed condensation between two indole (or 2-substituted indole) molecules with a suitable aldehyde under acid catalysis. Numerous catalysts and reaction media have been examined for the selective and high-yielding synthesis of BIMs with desired synthetic versatility, substrate scope, and process scalability.…”