Ruthenium-Catalyzed Selective Hydrogenation for Flavor and Fragrance Applications

Abstract

Due to the widespread use of unsaturated alcohols as final ingredients or synthetic intermediates in the flavor and fragrance industry, there is a very high demand for safe, productive and environmentally friendly methods to access olefins with high regio and stereocontrol in addition to efficient chemoselective reduction processes of carbonyl groups in the presence of olefin moieties. These two goals were achieved by developing industrial methodologies that respectively enable regio and stereoselective 1,4-hydrogenation reactions of conjugated dienes in the presence of catalytic amounts of both cationic cyclopentadienyl-type ruthenium(II) complexes and acidic additives along with chemoselective hydrogenations of ketones and aldehydes using chloro ruthenium(II) complexes bearing amino or iminophosphines ligands as precatalysts. In this contribution, we will display few examples of such achiral transformations that could efficiently be performed on up to multi-ton scale enabling Firmenich SA to produce in a sustainable manner some ingredients such as leaf alcohol, Polysantol®, Nirvanol®, Dartanol®, or Pamplewoodol® to be used in flavor and/or fragrance applications.