Silica-Gel–Catalyzed Efficient Synthesis of Quinoxaline Derivatives Under Solvent-Free Conditions
作者:Ganesh Chandra Nandi、Subhasis Samai、Ram Kumar、M. S. Singh
DOI:10.1080/00397910903576685
日期:2011.1.25
Quinoxalinederivatives have been prepared in good to excellent yields using silica gel as catalyst from various 1,2-diketones and 1,2-diamines undersolvent-freeconditions for the first time. The advantages of this method are short reaction time, reaction simplicity, convenient workup procedure, and purification of compounds by a nonchromatographic method.
Quinoxaline derivatives having bis(fluoromethyl), bis(chloromethyl), or bis(iodomethyl) groups at the 2- and 3-positions, and various electron-donating/withdrawing substituents at the 6- and/or 7-positions, were synthesized. Their antibacterial and antifungal activities were evaluated by means of minimum inhibitory concentration assays. The relationships between the substituents and the antimicrobial activities of the quinoxaline derivatives indicate that the electrophilicity of the halomethyl units plays an important role in generating the antimicrobial activity.
We synthesized 12 derivatives of 2,3-bis(bromomethyl) quinoxaline with substituents at the 6-and/or 7-positions, and evaluated their activities against bacteria and fungi. Of the 12 compounds, nine (1a-h, 1j, and 1k) showed antibacterial activity. The derivative 1g, which bears a trifluoromethyl group at the 6-position, showed the highest activity against Gram-positive bacteria, while 1c, which has a fluoro-group at the 6-position, showed the widest antifungal activity spectrum. However, only the derivative with an ethyl ester substitution, 1k showed activity against Gram-negative bacteria. (C) 2012 Elsevier Inc. All rights reserved.