I[C:2]1[CH:7]=[N:6][C:5]([C:8]2[CH:13]=[CH:12][C:11]([O:14][CH3:15])=[CH:10][CH:9]=2)=[CH:4][N:3]=1.[C:16]([Si:18]([CH3:21])([CH3:20])[CH3:19])#[CH:17]>C1COCC1.C(Cl)Cl.Cl[Pd](Cl)([P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.[Cu]I>[CH3:15][O:14][C:11]1[CH:12]=[CH:13][C:8]([C:5]2[CH:4]=[N:3][C:2]([C:17]#[C:16][Si:18]([CH3:21])([CH3:20])[CH3:19])=[CH:7][N:6]=2)=[CH:9][CH:10]=1A mixture of 2.30 g (7.37 mmol) 2-iodo-5-(4-methoxyphenyl)pyrazine and 1.56 mL (11.1 mmol) ethynyltrimethylsilane in 30 mL THF is charged with 0.12 g (0.15 mmol) bis(triphenylphosphine)dichloropalladium, 0.03 g (15.0 mmol) CuI and 3.01 mL (22.1 mmol) TEA. After stirring at r.t. for 4 h the reaction mixture is diluted with DCM and washed with 50 mL aq. 5% ammonia solution (1×) and 50 mL water (1×). The organic layer is dried with MgSO4 and the solvent is removed in vacuo. The residue is treated with PE/EtOAc (8/2), filtered through a plug of silica gel and the solvent is again removed in vacuo. The product is used without further purification.
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