It was found that the hydrogenation of 2, 3-dimethyl-5, 6-dihydropyrazine to form 2, 3-dimethylpiperazine resulted in the selective formation of only one of
cis- or
trans- isomers according to the kind of the reduction agent used. Reduction with sodium and ethanol only afforded the
trans compound, while that with lithium aluminum hydride gave the
cis compound alone. Catalytic reduction with Raney nickel, platinum oxide, or palladium-carbon chiefly afforded the
cis compound, with a minute amount of the
trans compound. Both
cis and
trans compounds, and their derivatives agree with Auwers-Skita's law.
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