Green Cyclocondensation of β-Ethylthio-β-indolyl-α, β-unsaturated Ketones with Semicarbazide Hydrochloride as Hydrazine Equivalent in Water: Aqueous Synthesis of 3-Pyrazolyl Indoles

A green and efficient cyclocondensation reaction of β-ethylthio-β-indolyl-α, β-unsaturated ketones with semicarbazide hydrochloride as hydrazine equivalent to prepare 3-pyrazolyl indoles had been developed in the presence of 3 equiv. of PEG-400 in reflux water. This procedure did not require toxic hydrazine and product purification, eliminating the use of toxic liquid chemicals.