Synthesis, characterization and catalytic assessment of novel hierarchical zeolite Hβ for the synthesis of biologically active amido alkyl naphthols

Abstract

Hierarchization of conventional zeolites is recently seen as one of the promising strategies to overcome diffusional restrictions and make entry and exit of bulkier reactant/product entities easy and possible within the zeolite framework. In this work, an attempt has been made to synthesize novel hierarchical zeolite Hβ using filtrate of alkali-treated zeolite Hβ as precursor and its subsequent treatment with cationic surfactant, 6-bromo hexyl trimethylammonium bromide (6-Br-TMA). The resultant hierarchical zeolite is characterized by several techniques that include, low- and high-angle X-ray diffraction (LXRD and HXRD), Fourier-transformed infrared (FTIR) spectroscopy, solid-state NMR (²⁹Si, ²⁷Al, and ¹H) and NH₃-temperature programmed desorption (NH₃-TPD) studies. Their surface area has been determined by N₂ sorption isotherms studies. The acidity of hierarchical zeolite was measured by NH₃-TPD. The catalytic activity of hierarchical HZβ is compared with parent microporous Hβ catalyst toward synthesis of amido alkyl naphthols (AANs) and its derivatives via multicomponent reaction. Also, two novel derivatives 3,5-dibromo-4-hydroxy AAN and 2-ethoxy AAN has been synthesized using 3,5- dibromo-4-hydroxy benzaldehyde and 2-ethoxy benzaldehyde, respectively, as the substituents. AAN derivatives are medicinally significant chemical scaffolds and are well-known for their use in variety of nucleoside antibiotics, as well as HIV protease inhibitors like Ritonavir and Lopinavir. It is well-known for its Brady cardiac activity, antiviral, antibacterial, antifungal, and antiparasitic effects.

Graphical abstract

Mesozeolite HZβ catalyzed synthesis of biologically active AANs