Synthesis of 1-(4-hydroxybutyl)-2-benzoyl indoles from 2-pyrrolidine benzaldehydes and -bromoacetophenones in deep eutectic solvent

A novel and highly efficient method for the synthesis of 1-(4-hydroxybutyl)-2-benzoyl indoles from 2-pyrrolidine benzaldehyde and alpha-bromoacetophenone in a choline chloride (ChCl)/ZnCl2 eutectic mixture was developed. This method, which does not require any catalyst, additive, or alkali, is useful for realizing tandem cyclization reactions. Several indoles were produced after cyclization and ring opening processes. Not all the compounds obtained are reported in the literature. This synthetic strategy proves that deep eutectic solvents can replace catalysts and organic solvents. Consequently, this is an environmentally friendly strategy that has significant potential in the development of green and sustainable chemistry.