Screening of Phosphine Ligands for Anti-Markovnikov Hydration of Alkynes

Hydration of C=C bond is a very efficient synthetic step. Currently, there exist ruthenium catalytical complexes, preferably with phosphine or bipyridine ligands, able to hydrate with, "anti-Markovnikov" selectivity, producing aldehydes. Although development of novel hydration catalysts was fruitful in recent years, only very few mechanistic studies of molecular structural influences are described. On the model hydration of 1-heptyne, we tested a series of various organophosphine ligands with various nitrogen functionalities having different acid-base properties. This screening showed that ligands with methylene-substituted nitrogen in five-membered ring are very promising to synthesize a catalyst for anti-Markovnikov hydration of alkynes.