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) A at 100 K.
Highlights
Several years ago we reported studies on 5,6-bis(bromomethyl)pyrazine-2,3-dicarbonitrile as a potential synthon for substituted azaphthalocyanines (AzaPcs) [1]
Molecules 2007, 12 substitute for the bromomethyl group, but pyrazines with chiral side chains would result from reactions with nucleophiles
A reaction between diaminomaleonitrile (1) and 2,5-dibromohexane-3,4-dione (2) [2], gave 5,6di(1-bromoethyl)pyrazine-2,3-dicarbonitrile (3) in approximately 83 % crude yield (Scheme 1). This product was a mixture of 5-(1-bromoethyl)-6-ethyl-pyrazine-2,3-dicarbonitrile and the two diastereomers of 3
Summary
Several years ago we reported studies on 5,6-bis(bromomethyl)pyrazine-2,3-dicarbonitrile as a potential synthon for substituted azaphthalocyanines (AzaPcs) [1]. Due to its extremely labile “benzylic” hydrogens, the dicarbonitrile was found to be too reactive towards base to be of general use. The branched 1-bromoethyl group, expected to be less reactive towards base, might be a good. Molecules 2007, 12 substitute for the bromomethyl group, but pyrazines with chiral side chains would result from reactions with nucleophiles. The objective of the present work was to prepare and explore 5,6-bis(1-bromoethyl)pyrazine-2,3dicarbonitrile (3) as a synthon for octa-substituted AzaPcs. Reactions of 3 with sodium sulfide followed by oxidation, were expected to give 5 via the corresponding dihydrothiophene derivative
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