Pd(0)-Catalyzed Asymmetric Intramolecular Grignard-Type Reaction of Vinyl Iodide-Carbonyl.

The insertion of carbonyl into C(sp 2 )-Pd(II) σ-bond (Grignard-type addition) was not established until the 1990s. While this elemental reaction has been well explored since then, its application in Pd(0) asymmetric catalysis remain elusive. Herein, we report the Pd(0)-catalyzed asymmetric intramolecular Grignard-type reaction of vinyl iodide-carbonyl in the presence of HCO 2 H additive, affording cyclic allylic alcohol with good to excellent enantioselectivity and diastereoselectivity. Mechanistic studies suggested that besides serving as an efficient reductant, HCO 2 H is also capable of facilitating protonation of the involved secondary alkoxyl-Pd(II), thus completely suppressing the β-H elimination. Moreover, no KIE was found in the competing reaction between vinyl iodide-aldehyde and 1-deuterated one, demonstrating the facile step of aldehyde insertion.