Ruthenium complex-catalyzed anti-Markovnikov hydration of terminal alkynes.

[reaction: see text]. Highly regioselective, efficient, and substituent-tolerant anti-Markovnikov hydration of terminal alkynes occurs to give n-aldehyde by use of a catalytic amount of easily available cyclopentadienylruthenium complexes bearing appropriate bidentate or monodentate phosphine ligands. Typically, RuCpCl(dppm) (1 mol %) catalyzes the addition of water to 1-hexyne at 100 degrees C to give hexanal in 95% yield: 2-hexanone is not detected at all.