Iridium-catalyzed crossed aldol coupling and a new concept to form an Ir–Si species

[Ir(COD)(PPh3)2]X (X=PF6, ClO4, and OTf) activated by H2 molecule catalyzes Mukaiyama-type aldol coupling between enoxysilanes and acetals or aldehydes. An Ir–Si species formed in the first stage of the catalytic cycle plays an important role in these reactions.