Efficient Nitrile Hydration Mediated by Ru

Efficient Nitrile Hydration Mediated by Ruⁱⁱ Catalysts in Micellar Media

Cavarzan, A., Venezia 30123, Scarso, A., Venezia 30123, Strukul, G., Venezia 30123

Prof. Strukul, Università ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy

When thinking about new environmentally friendly chemical processes, the solvent used is central. The amount of solvent normally constitutes the major part in the mass balance of a process, although its recovery is never quantitative. Nature performs biochemical reactions involved in life processes almost exclusively in water and this is also one of the key targets for synthetic chemistry. However, because of its poor capacity to dissolve most organic compounds, water has been neglected by chemists for years.¹ In devising the use of water as a reaction medium for catalyzed organic reactions, those in which water acts as a reagent seems particularly suitable. This is the case of nitrile hydration, that is the current industrial route to obtain acrylamide and other pharmaceutically interesting amides.

The reaction between water and the nitrile moiety requires catalysis with either Brønsted or Lewis acids capable of making nitrile more electrophilic and susceptible to nucleophilic attack by water. A plethora of metals has been tested to catalyze the reaction,² but the most effective one is Ru(II), for which ligand effects have been studied extensively. The reaction is usually performed in dioxane/water mixtures under harsh experimental conditions at temperatures close

or often above 100°C. The possibility to transfer this reaction in water appeared only recently in the literature,³ mainly using synthetically elaborate, water-soluble catalysts.^3d Herein we report an alternative approach based on the employment of surfactants to cope between catalyst and substrate solubilisation in water. So the use of [RuCl2(⁶- arene)(PR3)] complexes in micellar media provides high yields in amides (up to 97% for benzonitrile using neutral surfactants) and allows a facile catalyst tuning, exploring different ligands effects without the need to synthesize water soluble ligands. Excellent yields were obtained with ...(citare un po' di substrati) and the possibility to recycle the Ru(II) complex was evaluated.

Literature:

[1] Lindström U.M., Organic Reactions in Water 2007 Blackwell, Oxford [2] Kukushkin V.Y., Pombeiro A.J.L., Chem. Rev., 2002, 102, 1771.

[3] a) Koffi-Bie Djoman M.C., Ajjou A.N., Tetrahedron Letters 2000, 41, 4845. b) Kazuya Y., Mitsunori M., Noritaka M., Angewandte Chemie Int. Ed. 2004, 43, 1576 c).

Polshettiwar V., Varma R.S., Chem. Eur. J. 2009, 15, 1582 d) Cadierno V., Francos J., Gimeno J., Chem. Eur. J. 2008, 14, 6601 – 6605