Magnesium oxide nanoparticles as a recyclable catalyst for the green multicomponent synthesis of benzochromene derivatives

Chromenes are a common structural motif in variety of natural and non-natural products. Their derivatives have been known to exhibit a wide range of biological and pharmacological activities such as antioxidant, anticancer, antimicrobial, hypotensive and local anesthetic. In addition, they can be used as cognitive enhancers, for the treatment of neurodegenerative diseases, including Alzheimer s disease and schizophrenia disorder [1,2]. Heterogeneous catalysis has been in use since the start of organic chemistry. The activity and selectivity of these catalysts are enhanced by the surface of a support. Hence, the effective surface area of the reagent is increased significantly. The catalyst can be reused when recycled, although after some time it gets deactivated depending on its half-life. The main advantages of heterogeneous catalysts are the relative ease of catalyst separation from the product, recyclability, non-corrosiveness and tolerance of extreme operating conditions which makes them environmentally friendly [3,4]. In this work, a facile and efficient one-pot method has been developed for the synthesis of benzochromenes using MgO NPs as a heterogeneous catalyst by the condensation of aldehydes, β-naphthol and malononitrile in ethanol as solvent (Scheme 1). The reaction, with this catalyst was carried out under mild reaction conditions with very good to excellent yields.