Pheromone synthesis. Part 261: Synthesis of four pyrazines produced by females of the Korean apricot wasp, Eurytoma maslovskii

Four pyrazines were synthesized as sex specific volatiles of female Korean apricot wasp, Eurytoma maslovskii. They are 2,5-dimethyl-3-vinylpyrazine (1), 2,5-dimethyl-3-(2-methylpropyl)pyrazine (2), 2,5-dimethyl-3-(2-methylbutyl)pyrazine (3), and 2,5-dimethyl-3-(3-methylbutylpyrazine (4). They were synthesized in 74-85% yields by Pd- or Fe-catalyzed cross-coupling reactions between 3-chloro-2,5-dimethylpyrazine and CH2=CHBF3K or RMgBr. The present synthesis of 1 is the most reliable and scalable one to date.

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