Iridium-catalyzedZ-retentive asymmetric allylic substitution reactions

Keeping Z -olefins intact with iridium Transition metal catalysis offers a versatile means of modifying carbon centers adjacent to carbon-carbon double bonds. However, in the course of these reactions, the double bond tends to get weakened, allowing its substituents to swivel back and forth. Thus, if two large groups start out on the same side of the bond axis (a geometry known as a Z -olefin), they end up on opposite sides in the product. Jiang et al. report a chiral iridium catalyst that prevents this swiveling just long enough to substitute the adjacent carbon enantioselectively (see the Perspective by Malcolmson). Science , this issue p. 380 ; see also p. 345