acids to terminal alkynes under mild conditions affords (E)-α,β-unsaturated ketones with good yields. The reaction was achieved with chloro(1,5-cyclooctadiene)rhodium(I) dimer or chlorodicarbonylrhodium(I) dimer as catalytic precursor without additional phosphine as their use inhibits the reaction. Experiments using deuterated 1-hexyne discarded the possibility of a rhodium-vinylidene intermediate, thus