o-quinonoid heterocycles: Synthesis and crystal structure of 2,3-dicyano-5,7-bismethylthieno[3,4-b]pyrazine

Abstract

2,3-Dicyano-5,7-bismethylthieno[3,4-b]pyrazine (5), has been obtained as a minor product from reactions of S-nucleophiles with 5,6-di(1-bromoethyl) pyrazine-2,3-dicarbonitrile (3), or from a condensation of 4-hydroxy-2,5- dimethyl-2,3-dihydrothiophen-3-one (4) with diaminomaleonitrile. The molecular structure of compound 5 has been confirmed by X-ray diffraction. A partial separation of charge causes a donor-acceptor type arrangement of the planar molecules in uniform parallel stacks with an interplanar spacing of 3.334(2) Å at 100 K. © 2007 by MDPI.