(CTA)(3)[SiW12]-Li+-MMT: a novel, efficient and simple nanocatalyst for facile and one-pot access to diverse and densely functionalized 2-amino-4H-chromene derivatives via an eco-friendly multicomponent reaction in water

A simple, facile and highly efficient one-pot synthesis of a pharmaceutically interesting diverse kind of functionalized 2-amino-4H-chromene by a straightforward three-component reaction of an aromatic aldehyde, malononitrile (or ethyl cyanoacetate) and diverse enolizable C-H activated acidic compounds in the presence of a catalytic amount of (CTA)(3)[SiW12]-Li+-MMT is reported as a novel, environmentally friendly, reusable and promising nanocatalyst reaction in refluxing water. Based on the procedure, it was feasible to synthesize 2-amino-3-cyano-pyrano[3,2-c] chromen-5(4H)-one (4a-4y), 2-amino-3-cyano-pyrano[3,2-c] quinolin-5(4H)-one (6a-6s), 2-amino-3-cyano-7,8-dihydro-4H-chromen-5(6H)-one (8a-8u), 2-amino-3-cyano-pyrano[4,3-b] pyran-5(4H)-one (12a-12f), 2-amino-3-cyano-pyrano[3,2-c] pyridine-6(5H)-one (13a-13f), and 1H-pyrano[2,3-d] pyrimidine-2,4(3H, 5H)-dione (14a-14f). The structure of the nanocatalyst was confirmed by various techniques such as IR, SEM, TGA-DTG, EDX, ICP and XRD analyses. In comparison to the conventional methods, the salient features of the present protocol are green reaction conditions, high quantitative yields, short reaction time, high atom economy, low cost, easy isolation of products, and no column chromatographic separation.