A Ciappa

Homogeneous Asymmetric Catalysis in Fragrance Chemistry

Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide®, Phenoxanol®, Citralis®, and Citralis Nitrile®, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol®, Citralis®, and Citralis Nitrile® were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.

Asymmetric catalysis in fragrance chemistry: a new synthesis of Galaxolide®

Abstract A new synthesis of the olfactorally active stereoisomers of the musk odorant Galaxolide® is reported. The key step is the ruthenium-catalysed asymmetric hydrogenation of an α-aryl acrylic acid: asymmetric inductions up to 89% have been achieved using a catalytic system prepared in situ by mixing [Ru(benzene)Cl 2 ] 2 with ( S )-BINAP.