ARTICLE An efficient green synthesis and antibacterial activity of 1,3-benzoxazine and 1,3-naphthoxazine using NaCl.SiO 2 as solid catalyst in neat condition Putusenla Imchen 1 | Betokali K. Zhimomi 1 | Lensayula Longkumer 1 | Shokip Tumtin 2 | Toka Swu 3 | Tovishe Phucho 1 1 Department of Chemistry, Nagaland University, Zunheboto, India 2 Department of Chemistry, Kirori Mal College, Delhi University, Delhi, India 3 Department of Chemistry, Pondicherry University, Puducherry, India Correspondence Tovishe Phucho, Department of Chemistry, Nagaland University, Lumami 798627, Zunheboto, Nagaland, India. Email: itphucho@nagalanduniversity. ac.in Funding information Science and Engineering Research Board, Grant/Award Number: EEQ/2016/000260 dated 28-02-2017 Abstract A series of 1,3-oxazine derivatives were synthesized by a one-pot three- component (ie, phenol, formaldehyde, amine) method where SiO 2 bonded with NaCl was used as a reusable, more efficient, easily prepared, and available solid catalyst. The reactions were also carried out at room temperature for greener approach. in vitro studies for the synthesized compounds were also done against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli and Klebsiella pneumonia) to check for their applicability as an antibacterial agent where some of the synthesized com- pounds gives the best antibacterial activity against selected bacterial strains. Streptomycin was used as a standard control for all the microbial test. 1 | INTRODUCTION Oxazine, due to their wide and diverse range of biological activities are considered as an important type of heterocycles and are therefore, a special interest for the synthetic areas. The 1, 3-oxazine nucleus features prominently in many biologically important natural products and other bioactive molecules. [1–4] They have gained much importance due to their many biological activities like antitubular, [3] antibacterial, [4] anticancer, [5] anticonversant, [2] and analge- sic. [1] Benzo-1,3-oxazines are also generally known to pos- sess biologically properties like cytotoxic,, antianginal, antihypertensive effects, demonstrating antirheumatic, and antiosteoclastic bone resorption activity. [6] Multicomponent reactions (MCRs) have become highly efficient as they avoid time consumption, has eco- nomic purification processes, formation of several bonds in a single step and manufacture of complex molecular architectures. [7] This type of MCRs incorporate synthetic strategy as the products formed are obtained in just a single step and also its variation can be simply developed by changing the reacting components. [8] Recently, there is a consideration on the use and design of environmentally friendly heterogeneous catalysts to reduce the amount of toxic waste. Among them, nano scale metal oxides [9] have been efficiently used as catalysts for organic transformations. [10–12] Solid-support catalyst has become prominently important in the recent years as they are easily available/easily prepared and are generally less expensive. They can also be easily separated from reaction mixtures and can be reused which make them eco-friendly and also simple to use. This is one of the main reasons why silica-supported catalyst in MCRs has gained much importance and attention. [13] Gabbas et al also syn- thesized a series of 3,4-dihydro-2H-benzo- and naphtho- 1,3-oxazine derivatives using methylene bromide for ring- closure reaction where they also confirmed the presence of antibacterial property in almost all of their synthesized compounds via in vitro antimicrobial studies. [14a] As deriv- atives containing oxazine ring system have shown to Received: 10 December 2019 Revised: 27 April 2020 Accepted: 29 May 2020 DOI: 10.1002/jhet.4059 J Heterocyclic Chem. 2020;1–6. wileyonlinelibrary.com/journal/jhet © 2020 Wiley Periodicals LLC. 1