Acceleration under solvent-drop grinding: Synthesis of bis(indolyl)methanes using small amounts of organic solvents or ionic liquids

Abstract The reactions for the synthesis of bis(indolyl)methanes were accelerated by the addition of a few drops of solvents. Solvent effect for the addition of organic solvents and ionic liquids was examined. The yields of bis(indolyl)methanes increased by the addition of THF, 1-ethyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide ([emim]NTf2), and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6). Solvent-drop grinding methodology was quite useful for the reactions of “solid + liquid” as well as “solid + solid”.