o-Quinonoid Heterocycles: Synthesis and Crystal Structure of 23-Dicyano-57-bismethylthieno34-bpyrazine

摘要

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.