Useful Pd-Catalyst for Alkynylation of Aryl Triflates

　PdCl₂(alaphos) catalyst (1) is a complex of Pd(II) and a bidentate aminopropylphosphine ligand.¹⁾ Cross-coupling products are obtained in high yields by the reaction of aryl triflates with alkynyl Grignard reagents in the presence of 1 and LiBr. Aryl triflates as starting materials are readily prepared from the corresponding phenols, which is one of the advantages of this reaction. Furthermore, when an aryl triflate with a bromo group is used as a substrate, the alkynyl aryl bromide can be obtained with high functional group selectivity.²⁾ Alkynyl arenes are important compounds as building blocks of polycyclic aromatic hydrocarbons and as functional materials, so the coupling reaction with 1 is anticipated to be used widely.