Use of Hydrogen to Reduce Esters

Reduction of carboxylic acid esters to alcohols is usually achieved using stoichiometric amounts of hydride reducing agents, reactions which can be hazardous to scale. Work-ups on scale are often problematical and require great attention to detail. Now, chemists at the flavour/fragrance company Firmenich, in Switzerland have found a way to use hydrogen, using homogeneous ruthenium catalysts (Saudan L A et al, Angew Chem Int Ed, 2007, 46, 7473).

The procedure seems to work well with a variety of esters, including some which contain a double bond (though not in conjugation with the ester).

Of course industrial procedures to reduce esters to alcohols using hydrogen have long been practised, but conditions are severe (200-300oC, 200-300 bar) and only usually used for fatty esters. The new procedure appears to have a great scope and potential for scale-up.


 

 Trevor Laird