CaCl(2) as a bifunctional reusable catalyst: diversity-oriented synthesis of 4H-pyran library under ultrasonic irradiation.

Hamid Reza Safaei, Mohsen Shekouhy, Athar Shirinfeshan, Sudabeh Rahmanpur

Index: Mol. Divers. 16(4) , 669-83, (2012)

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Abstract

CaCl(2) is applied as an efficient reusable and eco-friendly bifunctional catalyst for the one-pot three-component synthesis of 4H-pyrans under ultrasonic irradiation. A broad range of substrates including the aromatic and heteroaromatic aldehydes, indoline-2,3-dione (isatin) derivatives, acenaphthylene-1,2-dione (acenaphthenequinone) and 2, 2-dihydroxy-2H-indene-1,3-dione (ninhydrin) were condensed with carbonyl compounds possessing a reactive α-methylene group and alkylmalonates. All reactions are completed in short times, and the products are obtained in good to excellent yields. The catalyst could be recycled and reused several times without any loss of efficiency.