title: Phosphino hydrazones as suitable ligands in the asymmetric Suzuki-Miyaura cross-coupling.
abstract: Phosphino hydrazones derived from C(2)-symmetric hydrazines exhibit excellent catalytic activity and provide good enantioselectivities in the asymmetric Suzuki-Miyaura cross-coupling to axially chiral biaryls, in particular for the most challenging reactions of monocyclic, functionalized aryl bromides and triflates. X-ray analysis of preformed [Pd(P/N)Cl(2)] precatalysts [(P/N) = phosphino hydrazone] revealed a strong n-π conjugation in the hydrazone moiety, identified by a high planarity degree at the pyrrolidine N(sp(3)) atom, that makes rotations around N-N bonds inconsequential. The complexes are also characterized by an envelope-like conformation with the Pd atom placed at the opposite side to the 2-phenyl group on the nearest stereogenic center of the pyrrolidine group. The isolation and structural analysis of oxidative addition intermediates indicate that the configurational stability of Pd-C(Ar) bonds is dependent on the substitution pattern in the aryl bromide.
authors.affiliation: Instituto de Investigaciones Químicas  (IIQ), CSIC/US, Américo Vespucio 49, 41092 Seville, Spain.
authors.forename: Abel
authors.initials: A
authors.lastname: Ros
authors.forename: Beatriz
authors.initials: B
authors.lastname: Estepa
authors.forename: Antonio
authors.initials: A
authors.lastname: Bermejo
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Alvarez
authors.forename: Rosario
authors.initials: R
authors.lastname: Fernández
authors.forename: José M
authors.initials: JM
authors.lastname: Lassaletta