Regio- and stereoselective addition of carboxylic acids to phenylacetylene catalyzed by cyclopentadienyl ruthenium complexes

The direct addition of carboxylic acids to terminal alkynes such as phenylacetylene in the presence of catalytic amount of [CpRu(CO)2Cl] (1) or [{CpRu(CO)2}2] (2) affords the anti-Markovnikov adducts with high selectivity. In most instances, the E-enol esters are the major products.