NbCl5 as an Expeditious Catalyst for the Synthesis of Quinoxalinyl and Dibenzodioxepinyl Phosphonates/Phosphinates via Michaelis-Arbuzov Reaction and their Biological Evaluation

Abstract

Background: Michaelis-Arbuzov reaction is one of the well studied reaction in phosphorus chemistry and used for the synthesis of phosphonates, phosphinates and phosphine oxides. Phosphonates are not only versatile intermediates in synthetic organic chemistry but also plays a vital role in biological activity. The usage of niobium(V) chloride as a catalyst has attracted the considerable attention due to its low hygroscopic character, high stability, cost effective, low loading and ease of handling. Methods: The present study describes the synthesis of a series of various aryl/heterocyclic substituted phosphonates/ phosphinates of 2-chloroquinoxaline 3(a-e) and 6-iododibenzo[d,f][1,3]dioxepine 5(a-e) using an expeditious catalyst, niobium(V) chloride by Michaelis-Arbuzov reaction and evaluated their antimicrobial and antioxidant activities. Results: A simple, efficient and new synthetic protocol was developed for the synthesis of quinoxalinyl and dibenzodioxepinyl phosphonate/phosphinate derivatives (3a-e/5a-e) in good yields using niobium(V) chloride as a catalyst. Biological data revealed that compound 5c exhibited potent antimicrobial activity and the compounds 3e and 5e good antioxidant activity. Conclusion: From the results it was concluded that niobium(V) chloride was an efficient catalyst for the synthesis of quinoxalinyl and dibenzodioxepinyl phosphonate/phosphinate derivatives and also exhibited good antimicrobial and antioxidant activities. Keywords: 2-chloroquinoxaline, 6-iododibenzo[d, f][1, 3]dioxepine, antimicrobial activity, antioxidant activity, aryl/heterocylic phosphonates, Michaelis-Arbuzov reaction, niobium(V) chloride catalyst.