Asymmetric Transfer Hydrogenation of Heterobicyclic Alkenes with Water as Hydrogen Source.

The asymmetric transfer hydrogenation of heterobicyclic alkenes was accomplished by using water as the sole hydrogen source. The transformation was co-catalyzed by Pd(OAc)2 /Zn(OTf)2 dual catalyst with metallic zinc as reducing agent. Various azabenzonorbornadienes and oxabenzonorbornadienes were transformed to the corresponding chiral 1,2-dihydronaphthalenes by the asymmetric reductive ring-opening reactions with good to excellent enantioselectivities.