An Efficient and Clean Synthesis of Thiophenyl Thiazole Depended Novel Triazolo[4,3-<i>a</i>]Quinoxaline Derivatives

Abstract

ABSTRACT.A simple and efficient approach for the synthesis of thiophenyl thiazole based triazolo [4,3-a]quinoxaline derivatives is described. In this methodology, 3-hydrazinyl-N-(4-(thiophen-2-yl)thiazol-2-yl)quinoxalin-2-amine derivatives treated with various aromatic aldehyde to form Schiff base which on treatment with iodobenzene diacetate in dichloromethane at room temperature to furnish title compounds. The synthesized compounds were characterized by 1 H NMR, 13C NMR, FT-IR, elemental analysis, and mass spectral data. INTRODUCTION1,2,4-triazoles are very interesting targets for medicinal and pharmaceutical applications. The recent literatures are enriched with progressive findings about the synthesis and pharmacological action of fused heterocyclic systems. The structural diversity and biological importance of nitrogen containing heterocyclic systems have made them attractive synthetic targets over many years and they are found in various natural products [1]. Quinoxalines are an important class of nitrogen containing heterocycles with a variety of biological activities. In particular quinoxaline scaffolds were found as a core unit in a number of biologically active compounds. These include anticancer [2,3], antibacterial [4], antiviral [5], anti-inflammatory [6], anti HIV [7,8] and antihelmintic activities [9]. Quinoxaline derivatives are also used in the development of novel organic dyes and organic semiconductors. Triazolo [4,3-a]quinoxaline [10] have been reported to possess antiviral, and antimicrobial activities. Many other triazolo quinoxaline derivatives have been reported [11][12][13] to possess other types of biological properties. Thus, triazolo quinoxaline derivatives continue to attract much attention as these molecules are of potential biological interest.For synthesis purpose, triazolo quinoxalines can be achieved in several ways. Reaction of 1-(2-chloroquinoxalin-3-yl)hydrazine and triethyl orthoformate gave triazolo quinoxaline [14]. Reactions of benzyl bromide or benzyl cinnamate with N-(benzotriazol-1-ylmethyl)arylimidoyl chlorides in the presence of t-BuOK occur with opening of the benzotriazole ring affording 1,2,4-triazolo[1,5-a]quinoxalines [15]. Reaction of N'-(1,2-dihydro-2-oxoquinoxalin-3-yl)benzohydrazide and HMPA formed triazolo quinoxaline [16]. By heating 2-hydrazino 3-phenylquinoxaline with phenyl-1,3-butanedione produced triazolo quinoxaline [17]. N-(2-chloro-4a,8a-dihydroquinoline3yl-methyl)-N-3-chloro-quinoxalin-2yl) hydrazones cyclised by iodobenzene diacetate under microwave irradiation technique to furnish the respective quinolinyl-1, 2, 4-s-triazolo [4,3-a]quinoxalines [18]. Here we report an efficient and clean synthesis of thiophene thiazole depended novel triazolo quinoxaline derivatives by cyclisation reaction. The constitutions of all the products were confirmed using 1 H NMR, 13C NMR, FTIR, and elemental analysis. EXPERIMENTALRequired all reagents were obtained commercially. Solvents were purified and dried before being used. All melting points were taken in open ...