Sonogashira reaction of heteroaryl halides with alkynes catalysed by a palladium-tetraphosphine complex

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/(1/2)[PdCl(C3H5)]2 system catalyses the Sonogashira reaction of heteroaryl halides with a range of alkynes with moderate to high substrate/catalyst ratios in good yields. A variety of heteroaryl halides such as pyridines, quinolines, a pyrimidine, an indole, thiophenes, or a thiazole have been used successfully. The reaction also tolerates several alkynes such as phenylacetylene and alk-1-ynols. The nature of the heteroaromatics and the substituent of the alkynes have both an important effect on the reaction rates. High reaction rates were generally observed with phenylacetylene. With this alkyne substrate/catalyst ratios up to 10,000 have been used successfully. An effect of the position of the alcohol function on the reaction rates was observed with alk-1-ynols. Higher substrate/catalyst ratios could be used with but-3-yn-1-ol, pent-4-yn-1-ol or hex-5-yn-1-ol than with propargyl alcohol. The nature and the position of the halide on the heteroaromatics have also an important effect on the reaction rates. As expected, higher reaction rates were obtained with heteroaryl iodides than with heteroaryl bromides or chlorides.

Figure optionsDownload as PowerPoint slide