Efficient and Eco‐Friendly Process for the Synthesis of Bis(1H‐indol‐3‐yl)methanes using Ionic Liquids

Abstract

Indoles react smoothly with carbonyl compounds in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ) or 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF 6 ) ionic liquids under mild reaction conditions to afford the corresponding bis-indolylmethanes in excellent yields. These ionic liquids can be recovered and recycled in subsequent reactions without any apparent loss of activity.

Synthesis of Polyarylated Methanes through Cross‐Coupling of Tricarbonylchromium‐Activated Benzyllithiums

“…[27] In contrast, F-C chemistry strongly favors reaction of indole at the 3-position (or 2-position if the 3-position is blocked). [5,[11][12][13]17] Polyarylmethane derivatives bearing privileged indoles have attracted interest due to their widespread occurrence in biologically active compounds.…”

“…Polyarylated methanes are attracting considerable attention due to their growing importance in developing medicinal agents for cancer [1] and vascular disease, [2,3] as well as in leuco dye precursors, [4,5] photochromic agents, and applications in materials science. [6,7] Most syntheses of polyarylmethanes involve Friedel-Crafts-type (F-C) electrophilic aromatic substitution reactions, [5,6,[8][9][10][11][12][13] although there are some limited exceptions. [4,14,15] Recently, modified F-C processes, [9,16] including a novel copper-catalyzed aza-Friedel-Crafts variant, [17] have been used in the preparation of diversely substituted triarylmethanes.…”

A Convenient Synthesis of 3,7′-Bisindole Derivatives

“…Generally, Lewis acids as well as Brønsted acids are employed as catalysts to form bisindole derivatives starting from indoles reacted with carbonyl compounds and their synthetic equivalents [19,20,21,22,23,24,25,26,27,28,29]. However, the synthetic pathways of highly functionalized bisindole derivatives usually suffer from common limitations, including harsh reaction conditions, multistep reactions, use of toxic solvents, and costly catalysts or enzymes [30].…”

Iodine-catalyzed $$\hbox {sp}^{3}$$ sp 3 C–H bond activation by selenium dioxide: synthesis of diindolylmethanes and di(3-indolyl)selanides

“…DIMs are usually synthesized from the reaction of indoles with aldehydes or ketones in the presence of protic acids [11], Lewis acids [12][13][14], rare earth catalysts [15,16], and ionic liquids [17,18]. Very recently, Shiri et al published a review article on DIMs [19].…”