Dimethyl and diethyl esters of 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carb-oxy-lic acid: a comparison

• Published in: Acta crystallographica. Section E, Crystallographic communications Vol. 72; no. Pt 2; pp. 233 - 237
• Main Authors: Alfonso, Montserrat, Stoeckli-Evans, Helen
• Format: Journal Article
• Language: English
• Published: England International Union of Crystallography 01.02.2016
• Subjects: Research Communications; pyrazine; di­carb­oxy­lic acid; dimeth­yl; crystal structure; pyridine; dieth­yl; C—H⋯O and C—H⋯N hydrogen bonding
• DOI: 10.1107/S2056989016001080
• ISSN: 2056-9890

In dimethyl 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ate, C18H14N4O4, (I), and diethyl 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ate, C20H18N4O4, (II), the dimethyl and diethyl esters of 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carb-oxy-lic acid, the orientation of the two pyridine rings differ. In (I), pyridine ring B is inclined to pyrazine ring A by 44.8 (2)° and the pyridine and pyrazine N atoms are trans to one another, while pyridine ring C is inclined to the pyrazine ring by 50.3 (2)°, with the pyridine and pyrazine N atoms cis to one another. In compound (II), the diethyl ester, which possesses twofold rotation symmetry, the pyridine ring is inclined to the pyrazine ring by 40.7 (1)°, with the pyridine and pyrazine N atoms trans to one another. In the crystal of (I), mol-ecules are linked by C-H⋯N hydrogen bonds, forming chains along [001]. The chains are linked by C-H⋯π inter-actions, forming a three-dimensional structure. In the crystal of (II), mol-ecules are linked via C-H⋯O hydrogen bonds, forming a three-dimensional framework. There are C-H⋯π inter-actions present within the framework.