An Ir/Zn dual catalysis has been
developed for the enantio- and
diastereodivergent α-allylation of unprotected α-hydroxyketones
under mild conditions, in the absence of any additional base. The
cooperative action of a chiral iridium complex derived from phosphoramidites
and a chiral Zn-ProPhenol complex is most likely responsible for its
high reactivity, excellent enantioselectivity (up to >99% ee),
and
good diastereoselectivity (up to >20:1 dr). All four product stereoisomers
could be prepared from the same set of starting materials and under
identical conditions by simple selection of appropriate catalyst combinations
