Replacing halogenated solvents by a butyl acetate solution of bisphenol S in the transformations of indoles

A butyl acetate solution of bisphenol S (BPS) was proved to be able to replace hazardous halogenated solvents in the transformation of indoles. Measurement with Kamlet-Taft solvatochromic parameters disclosed that the polarity of the BPS-containing butyl acetate was enhanced greatly. The protocol not only conferred a convenient way to minimize the use of halogenated solvents in the synthesis of indole derivatives, but also enabled successful recycling of both the butyl acetate solvent and BPS additive, strengthening the greenness of the reaction systems. A polarity-enhanced mixture solvent containing BPS in BuOAc is capable of replacing hazardous halogenated solvents in the conversion of indoles.