Synthesis of 3,3'-Dichloro-2,2'-bipyrazine

The reaction of 2-chloropyrazine with 0.5 equivalent of lithium diisopropylamide (LDA) was examined. Although we expected 3-chloro-2,2'-bipyrazine as the main product, 3,3'-dichloro-2,2'-bipyrazine was obtained in low yield (7%). The reaction was not clean and considerable amount of intractable precipitates and several byproducts were formed. Among them, 3,3',3'''-trichloro-2,2':5',2'':6'',2'''-quarterpyrazine was isolated and unambiguously identified by X-ray crystallographic analysis.