Cross-Coupling Reactions of Chloropyrazines with 1-Substituted Indoles

Palladium-catalyzed coupling reactions of 2-chloro-3, 6-dialkylpyrazines with 1-tosylindole gave 1-tosyl-3-(3, 6-dialkylpyrazin-2-yl)indoles as the main product in each case. The subsequent hydrolysis of the products yielded the corresponding 3(3, 6-dialkylpyrazin-2-yl)indoles under alkaline conditions. Coupling reactions of 2-chloro-3, 6-dialkyl-pyrazines with 1-methyl- or 1-benzylindole occurred at the 2-position of the indoles, but 2-chloro-3, 5-diphenylpyrazine (1e) failed to react with 1-methylindole.