Highly Enantioselective Pd-Catalyzed Synthesis of P‑Stereogenic Supramolecular Phosphines, Self-Assembly, and Implication

Metal-catalyzed
asymmetric addition of a secondary phosphine to
an aryl halide is one of the most efficient and reliable approaches
for the construction of enantiopure carbon–phosphorus bonds.
An isolated Pd­(II) complex (5) catalyzes the carbon–phosphorus
coupling reaction between tolylphenylphosphine (1a) and
3-iodophenylurea (2b), which proceeds with an unprecedented
enantiomeric excess (ee) of 97%. The generality of the strategy has
been demonstrated by preparing a small library of a new class of P-stereogenic
phosphines with an in-built hydrogen bonding motif for the first time.
The P-stereogenic phosphines self-assemble on a metal template via
deliberately installed hydrogen-bonding motifs and mimic the bidentate
ligand coordination. Interestingly, when it was employed in asymmetric
hydrogenation, the supramolecular phosphine {1-(3-(phenyl­(o-tolyl)­phosphanyl)­phenyl)­urea} (6b) produced
the corresponding hydrogenated product with the highest enantiomeric
excess of 99% along with excellent conversion, demonstrating the potential
of these enantioenriched P-chirogenic supramolecular phosphines in
asymmetric catalysis.