Asymmetric Pt(II)-catalyzed ene reactions: counterion-dependent additive and diphosphine electronic effects.
[reaction: see text]. Catalysis of the glyoxylate-ene reaction by dicationic P2Pt(II) complexes is subject to anion-dependent additive effects. For [((S)-MeOBiphep)Pt](OTf)2 catalysts, acidic phenols such as 3-CF3-C6H3OH or C6F5OH provide substantial rate increases but do not affect the more active SbF6-based catalysts. Enantioselectivity and reactivity also increased with diphosphine basicity, with 4-t-Bu-substituted MeOBiphep ligands yielding the highest enantioselectivities.
Koh
J H
JH
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
Larsen
A O
AO
Gagné
M R
MR
D000838:Anions; D007477:Ions; D008024:Ligands; D008956:Models, Chemical; D019800:Phenol / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*
D000838:Anions; D007477:Ions; D008024:Ligands; D010720:Phosphines; D019800:Phenol; D010984:Platinum