Henri B. Kagan
Wolf Prize Laureate in Chemistry 2001
Henri B. Kagan
Affiliation at the time of the award:
University of Paris-South, France
“for their pioneering, creative and crucial work in developing asymmetric catalysis for the synthesis of chiral molecules, greatly increasing mankind’s ability to create new products of fundamental and practical importance”.
Professors H. B. Kagan, R. Noyori and K. B. Sharpless, have independently made great advances in developing the ability to synthesize chiral molecules. They pioneered the use of chiral molecular metal complexes as catalysts in asymmetric synthesis. Minute amounts of such catalysts can enable the production of large amounts of desired products of controlled handedness. These catalysts can perform various molecular transformations in an asymmetric fashion, such as reduction, oxidation and isomerization, leading to a variety of useful chiral products.
The chiral synthetic advances made by these three scientists, working on three different continents but pursuing the same significant goals, are critical to pharmaceutical manufacturing and the preparation of a very large number of molecules of controlled handedness. Their pioneering work has revolutionized our understanding of asymmetric catalysis and provided the means for efficient industrial and laboratory preparations of important pharmaceutical products and fine chemicals needed for daily life.
The first example of asymmetric catalysis (cyclopropanation) by a well-defined metal (copper) complex was reported by Noyori in 1966. Although only a low enantiomeric excess was obtained, the result stimulated further research. In 1971, Kagan reported a breakthrough in catalytic enantioselectivity. Using a C2- symmetric ligand (DIOP) for the first time, he obtained a very high enantiomeric excess in alkene hydrogenation, catalyzed by a rhodium complex. Kagan´s work had a strong influence on the course of research in the field of asymmetric catalysis, leading to the development of a variety of C2 -symmetric ligands and stimulating the study of several important reactions, such as asymmetric hydrogenation, hydroformylation, hydrosilylation and allylic alkylation. In 1980, Noyori reported asymmetric catalysis, by complexes of a new diphosphine ligand, BINAP. Catalysis by ruthenium and rhodium complexes of this ligand, resulted in spectacular laboratory and commercial applications, in asymmetric hydrogenation and isomerization. In the same year, Sharpless reported a breakthrough in the important field of asymmetric oxidation. His general method for the highly enantioselective epoxidation of allylic alcohols catalyzed by a titanium complex, is of broad scope and is used routinely in synthesis. More recently, Sharpless developed another highly useful synthetic methodology, the asymmetric dihydroxylation of alkenes, catalyzed by an osmium complex.