synthesis of quinoxaline 1,4-di-n-oxide analogues and crystal structure of 2-carbomethoxy-3-hydroxyquinoxaline-di-n-oxide喹喔啉的合成1,4-di-n-oxide类似物和2-carbomethoxy-3-hydroxyquinoxaline-di-n-oxide的晶体结构.pdf

Molecules 2011, 16, 6894-6901; doi:10.3390/molecule OPEN ACCESS molecules ISSN 1420-3049 /journal/molecules Article Synthesis of Quinoxaline 1,4-di-N-Oxide Analogues and Crystal Structure of 2-Carbomethoxy-3-hydroxyquinoxaline-di-N-oxide Yingjun Xu, Fanhong Wu, Zhiyi Yao *, Minmin Zhang and Sheng Jiang College of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 200235, China * Author to whom correspondence should be addressed; E-Mail: xuyj@; Tel./Fax: +86-21 Received: 28 June 2011; in revised form: 3 August 2011 / Accepted: 8 August 2011 / Published: 12 August 2011 Abstract: A series of quinoxaline 1,4-di-N-oxide analogues were prepared from benzofurazan N-oxide derivatives and β-diketone ester compounds by the improved Beirut reaction. The structures of the target products were characterized by NMR, MS, IR and elemental analysis measurements, and that of 2-carbomethoxy-3-hydroxyquinoxaline- di-N-oxide was further confirmed by single-crystal X-ray diffraction. Its crystal structure belongs to the monoclinic system, space group C2/c with a = 14.4320 (12) Å, b = 10.7514 (9) Å, c = 13.2728 (11) Å, V = 1958.5 (3) Å 3 , Z = 8. The X-ray crystallographic analysis reveals that quinoxaline 1,4-di-N-oxide displays acyloin-endiol tautomerism. Keywords: quinoxaline 1,4-di-N-oxide; Beirut reaction; acyloin-endiol tautomerism 1. Introduction Some quinoxaline 1,4-di-N-oxides and their derivatives are usef