Iridium catalysts for the asymmetric hydrogenation of olefins with nontraditional functional substituents

Chiral iridium catalysts have now been used in the asymmetric hydrogenation of largely unfunctionallized olefins for a decade. Recently, they have also been applied to substrates with more exotic functional groups, including non-coordinating ones. These, unlike coordinating substituents, cannot direct asymmetric hydrogenation by rhodium- or ruthenium-based catalysts. This review discusses several classes of these less familiar substrates, outlines the progress that has been made toward their stereoselective hydrogenation, and highlights the role of iridium complexes in this emerging field. We hope this will inspire researchers to consider iridium-catalyzed asymmetric hydrogenation as a potential route to a broad range of chiral compounds. (c) 2007 Elsevier B.V. All rights reserved.