TAILIEUCHUNG - Synthesis and structure of some azolium salts
The reactions between benzimidazole, imidazole, or 1,2,4-triazole with either benzyl chloride or isopropyl bromide yielded 6 azolium salts, namely 1,3-dibenzylimidazolium chloride (M1), 1,3-dibenzylbenzimidazolium chloride (M2), 1,3-dibenzyl-1,2,4-triazolium chloride (M3), 1,3-diisopropylimidazolium bromide (M4), 1,3- diisopropylbenzimidazolium bromide (M5), and 1,3-diisopropyl-1,2,4-triazolium bromide (M6). These salts can be further used as the starting compounds for the synthesis of complexes based on N-heterocyclic carbenes for various applications. The structures of M1÷M6 have been unambiguously determined by means of IR and 1H NMR spectroscopic methods. | Vietnam Journal of Chemistry, International Edition, 55(2): 248-253, 2017 DOI: Synthesis and structure of some azolium salts Pham Van Thong, Nguyen Hien, Nguyen Son Ha, Nguyen Thi Thanh Chi* Faculty of Chemistry, Hanoi National University of Education Received 8 December 2016; Accepted for publication 11 April 2017 Abstract The reactions between benzimidazole, imidazole, or 1,2,4-triazole with either benzyl chloride or isopropyl bromide yielded 6 azolium salts, namely 1,3-dibenzylimidazolium chloride (M1), 1,3-dibenzylbenzimidazolium chloride (M2), 1,3-dibenzyl-1,2,4-triazolium chloride (M3), 1,3-diisopropylimidazolium bromide (M4), 1,3diisopropylbenzimidazolium bromide (M5), and 1,3-diisopropyl-1,2,4-triazolium bromide (M6). These salts can be further used as the starting compounds for the synthesis of complexes based on N-heterocyclic carbenes for various applications. The structures of M1÷M6 have been unambiguously determined by means of IR and 1H NMR spectroscopic methods. Keywords. N-heterocyclic carbenes, azoles, azolium salts. 1. INTRODUCTION In the past few years, transition metal complexes of N-heterocyclic carbene ligands (NHCs) have found vast application in molecular catalysis, material science, and medicine [1, 2]. Recently, researchers have also coupled their photo emissivity with anti-cancer activity and demonstrated their potential use towards lifesaving chemo-theranostic treatment [3]. In particular, palladium(II) complexes bearing carbine ligands derived from imidazolium precursors have been successfully developed as highly active precatalysts for C-C coupling reactions such as Mizoroki – Heck and Suzuki – Miyaura cross-coupling as well as CO-olefin copolymerization [4, 5]. Among many ways to synthesize NHC complexes, in-situ deprotonation of azolium salts with a basic metal precursor is one of the most widely used method due to its simplicity and efficiency [6, 7]. In this article, we describe the synthesis and .
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