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The palladium-catalyzed cross-coupling reaction of 2-chloropyrazines with indole was shown to proceed in moderate to good yields, giving 2-(pyrazin-2-y1)indoles.The structure determination of the products was made on the basis of the X-Ray diffraction and 1 3 ~-~~~ spectroscopic analyses.The palladium-catalyzed coupling reactions of indoles have been extensively 1 investigated in recent years .Among these reactions, allylation2 prompted us to 3 pay attention to the synthesis of the Cypridina luciferin .Recently, we reported the simple procedures for the introduction of the cyano4, alkenyl and alkyny15, 6 and methyl groups into the pyrazine ring by the aid of the palladium catalysts.Our attempt was to couple chloropyrazines with indole to prepare 3-(pyrazin-2-y1)indoles, which constitute the carbon skeleton of the Cypridina luciferin, isolated from Cypridina hilgendorf ii3.When a mixture of 2-chloro-3,6-diisobutylpyrazine (Id), indole, potassium acetate and tetrakis(tripheny1phosphine)palladium in N,N-dimethylformamide (DMF) was refluxed for 6 h, the coupling product (Zd) was obtained in 25% yield.By replacing the solvent by N,N-dimethylacetamide (DMA) and by elongating the reaction time to 12 h, the yield became to 49%.Thus, some other 2-chloro-3,6dialkylpyrazines (la-c) were submitted to the reaction under the same conditions and the results are shown in Table 1.On the other hand, the reaction of Z-chlorodiphenylpyrazines with indale was achieved successfully, by replacing the catalyst HETEROCYCLES.V-I. 23, No. 9, 1985 111.0 (indole C-7), 120.0 (indole C-6), 121.5 (indole C-4), 123.7 (indole C-5), 129.2 (indole C-9), 134.0 (indole C-2), 136.0 (indole C-8), 140.6 (pyrazine C), 143.2 (pyrazine C), 148.3 (pyrazine C), 149.6 (pyrazine C) ppm; Anal.Calcd.for C14H13N3: C, 75