alpha-casein: an efficient, green, novel, and eco-friendly catalyst for one-pot multi-component synthesis of bis (pyrazol-5-ols), dihydro-pyrano[2,3-c]pyrazoles and spiropyranopyrazoles in an environmentally benign manner

For the first time, alpha-casein was used as an efficient and eco-friendly catalyst for an effective and facile preparation of dihydropyranopyrazoles and spiropyranopyrazoles. the synthesis of bis (pyrazol-5-ols) derivatives was developed via one-pot, pseudo-five-component condensation, and the target dihydropyrano[2,3-c]pyrazoles and spiropyranopyrazoles were prepared by one-pot four-component reaction. this new method of employing alpha-casein, which is a green, recyclable, non-toxic and commercially available catalyst, offers advantages such as mild condition, short reaction times, easy work-up, no need for column chromatography, and high yields of the products which make it more economic than other environmentally synthetic protocols.