An additional coordination group leads to extremely efficient chiral iridium catalysts for asymmetric hydrogenation of ketones.

The production of enantiopure chiral compounds is important for pharmaceutical and agrochemical industries because enantiomers can exhibit distinct biological activities. Therefore, processes that directly produce the desired enantiomer are desirable. First reported by Knowles, Horner et al. in 1968, catalytic asymmetric hydrogenation of unsaturated compounds such as olefins, ketones, and imines is one of the most commonly used methods for producing enantiopure chiral compounds. Great progress has been made in this field, and many chiral catalysts are developed for a wide range of unsaturated substrates. It is noteworthy that some of these synthetic chiral catalysts, which are much smaller and simpler than enzymes, exhibit activities and selectivities comparable to those of enzymes: in some cases, one molecule of catalyst can produce millions of new molecules enantioselectively. For example, the diphosphine/diamine ruthenium catalyst reported by Noyori et al. and the iridium ferrocenyl catalyst Ir-(R,S)Xyliphos developed by a team from Novartis (Scheme 1)