An efficient synthesis of 3-substituted indole derivates under ultrasound irradiation

► The use of equimolar substrates, environmentally benign reaction conditions, as well as facility of scale-up enable the advantages and potentials to this methodology. ► This study offers an efficient, solvent-free synthesis of 3-substituted indole derivates under ultrasound irradiaon. ► The use of 2-chlorethanol as a mild acidic promoter supports the practical utility of this procedure for a wide variety indoles and nitroalkenes. ► The use of equimolar substrates, environmentally benign reaction conditions, as well as facility of scale-up enable the advantages and potentials to this methodology A solvent-free procedure for the synthesis of 3-substituted indole derivates from indoles and nitroalkenes under ultrasound irradiation is described. Control experiments disclosed besides mechanical effects, namely agitation, sonochemical effects are the main forces to drive the reaction. In the method, 2-chloroethanol was used to prepare a wide variety of 3-substituted indole derivates. This procedure only need equimolar amounts of reaction substrates and can be readily scaled up.