A highly efficacious method for the synthesis of spiro-4H-pyran and 4H-pyran derivatives using BQC as the catalyst and investigating on their in vitro antibacterial activity

Abstract

This study for the first time investigates the catalytic properties of 1-benzylquinolinium chloride (BQC) as a molten salt catalyst, in contrast to its previous role as a reactant. This investigation is focused on the reaction of quinoline and benzyl chloride, which was carried out under environmentally friendly conditions in an aqueous medium, resulting in the formation of 1-BQC. Various analytical techniques such as FT-IR, CHN, Mass, TGA, FESEM, ¹H NMR, and ¹³C NMR have been utilized to scrutinize the properties and characteristics of the catalyst. Subsequently, the application of the reagent to expedite the synthesis through a one-pot, three-component reaction of spiro-2-amino-3-cyano-4H-pyrans and 2-amino-3-cyano-4H-pyrans derivatives as momentous compounds with substantial biological and pharmaceutical activities, was meticulously examined. The proposed method has numerous merits, encompassing uncomplicated catalyst preparation, high efficiency, truncate reaction duration, simplicity of the process, ease of separation from the reaction mixture without the necessity for column chromatographic separation, utilization of commercially available starting materials, and recyclability of the catalyst for multiple times. Using the agar well diffusion procedure, the in vitro antibacterial activity of this catalyst along with its two primary components and two new derivatives (4 and 5) has been evaluated in the reaction of spiro-2-amino-3-cyano-4H-pyran versus Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive).

Graphical abstract