Camphor sulfonic acid catalyzed facile and general method for the synthesis of 3,3'-(arylmethylene)<i>bis</i>(4-hydroxy-2<i>H</i>-chromen-2-ones), 3,3'-(arylmethylene)<i>bis</i>(2-hydroxynaphthalene-1,4-diones) and 3,3'-(2-oxoindoline-3,3-diyl)<i>bis</i>(2-hydroxynaphthalene-1,4-dione) derivatives at room temperature
Gurpreet Kaur, Diksha Singh, R. Arvind Singh, Bubun Banerjee
Abstract
Camphor sulfonic acid catalyzed a straightforward, efficient, and general method has been developed for the synthesis of 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones), 3,3'-(arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) and 3,3'-(2-oxoindoline-3,3-diyl)bis(2-hydroxynaphthalene-1,4-dione) derivatives in aqueous ethanol at room temperature from the reactions of various aromatic aldehydes and 4-hydroxycoumarin or 2-hydroxynaphthalene-1,4-dione respectively. Mild reaction conditions, use of metal-free organocatalyst, good to excellent yields, high atom-economy, environmentally benign, easy isolation of products, and no column chromatographic separation are some of the major benefits of this developed protocol.