Facile stereoslective synthesis of spiro[indole-oxiranes] by combination of phase transfer catalyst and ultrasound irradiation and their bioassay

An alternative and environmentally benign pathway for diastereoslective synthesis of fluorinated spiro[indole-3,2′-oxirane]-3′-benzoyl-2(1H)-ones (2a–g) is reported. The spiro[indole-3,2′-oxiranes] derivatives were obtained in 90–97% yield exclusively via the epoxidation of 3-aroylmethylene indole-2-ones with 30% aqueous hydrogen peroxide using cetyltrimethyl ammonium bromide as a phase transfer catalyst under ultrasound irradiation. The lead compounds have been tested for their antimicrobial activity and antioxidant properties.

Research highlights
► Environmentally benign pathway for diastereoselective synthesis.
► Ammonium cetyletrimethylammonium bromide catalyzed efficiently.
► Methodology is simple procedure, low cost, easy work-up, short reaction times, and milder conditions.
► Compounds showed antimicrobial activity and antioxidant properties.