Ruthenium-catalyzed selective anti-Markovnikov trans addition of carboxylic acids and tail-to-tail dimerization of terminal alkynes

Carboxylic acids react with terminal alkynes in the presence of a catalytic amount of RuClx(p-cymene)(triazol-5-ylidene) to selective generate Z-alk-1-en-1-yl esters. The anti-Markovnikov and trans addition on the terminal alkyne gives access to Z-alkene derivatives of phenylacetylene, t-butylacetylene, 1-octyne, 4-pentynoic acid and 1,7-octadiyne. The dimerization of terminal alkynes catalyzed with the same Ru-complex gives preferentially tail-to-tail coupling reactions.