na2edta: an efficient, green and reusable catalyst for the synthesis of biologically important spirooxindoles, spiroacenaphthylenes and spiro-2-amino-4h-pyrans under solvent-free conditions

For the first time, the organic salt na2edta was used as a catalyst for an effective and facile preparation of spiro-4h-pyrans via single-pot three-component condensation of isatin/acenaphthoquinone/ninhydrin, malononitrile, and ch-acids through knoevenagel–michael–annulation sequence. this new protocol employing na2edta, which is a green, recyclable, and inexpensive catalyst, offers advantages such as solvent-free and highly efficient reaction conditions, short reaction times (10–15 min), easy work-up and high yields which make it more economic than other environmentally synthetic methods.