A catalyst-free one-pot four component methodology for the synthesis of 2H-indazolo[2,1-b]phthalazinetriones
under ultrasonic irradiation at room temperature using 1-butyl-3-methylimidazolium bromide,
[Bmim]Br, as a neutral reaction medium is described. A broad range of structurally diverse aldehydes
(aromatic aldehydes bearing electron withdrawing and/or electron releasing groups as well as heteroaromatic
aldehydes) were applied successfully, and corresponding products were obtained in good to
excellent yields without any byproduct.