Direct Synthesis of Heteroarylethynes via Palladium-catalyzed Coupling of Heteroaryl Halides with EthynylzincHalides. Its Application to an Efficient Synthesis of a Thiophenelactone from Chamaemelum nobile L.

A variety of terminal allcynes containing a heteroaryl group can be directly and selectively synthesized by the Pd-catalyzed coupling of heteroaryl iodides or bromides with ethynylzinc halides.Various compounds of this class containing furan, thiophene, and pyridine have been prepared, and the procedure has been applied to an efficient and selective synthesis of a thiophenelactone from Chamaemelum nobile L.We have recently reported a direct synthesis of tenninal alkynes via Pd-catalyzed coupling of aryl and alkenyl halides, in particular iodides, with ethynylmetals containing Mg and ~n ' based on our earlier ~t u d i e s .' ~