P-Stereogenic monophosphines with the 2-p-terphenylyl and 1-pyrenyl substituents. Application to Pd and Ru asymmetric catalysis

• P-stereogenic monophosphines with a polycyclic aromatic substituent.
• Neutral and cationic allylic Pd complexes: [PdCl(η3-allyl)P], [Pd(η3-allyl)P2]PF6.
• Neutral Ru complexes: [RuCl2(η6-p-cymene)P].
• Pd-catalysed hydrovinylation of styrene and allylic substitution reactions.
• Ru-catalysed hydrogen transfer of acetophenone.

The synthesis of five optically pure P-stereogenic monophosphines of the type PPhArR (Ar = 2-p-terphenylyl (a), 1-pyrenyl (b); R = OMe, Me, i-Pr) is described. The ligands were fully characterised and the absolute configurations of PPh(1-pyrenyl)R (3b and 5b; R = OMe and Me respectively) were confirmed by X-ray diffraction. The complexation of the monophosphines to Pd and Ru organometallic units yielded the neutral complexes [PdCl(η3-2-Me-allyl)P] (10–12) and [RuCl2(η6-p-cymene)P] (16–18). Complete characterisation, including the crystal structure determination of [RuCl2(η6-p-cymene)(PMePh(2-p-terphenyl))] (17a) is provided. Neutral palladium complexes appeared as mixtures of two diastereomers in solution according to NMR. The synthesis and characterisation of four cationic [Pd(η3-2-Me-allyl)(P)2]PF6 (13 and 14) is also described. The application of neutral Pd complexes to catalytic styrene hydrovinylation afforded moderate conversions, high chemoselectivities (>92%) to 3-phenyl-1-butene and up to 43% ee with precursor 12a. Cationic Pd complexes were tested as catalytic precursors in allylic substitution of rac-3-acetoxy-1,3-diphenyl-1-propene (rac-I), with the anion of dimethylmalonate and benzylamine as nucleophiles, obtaining full conversions and up to 80% ee in alkylation and 60% ee in amination with precursor 13a. Finally, ruthenium complexes were used as catalytic precursors in transfer hydrogenation of acetophenone, with complete conversions after several hours but low enantioselectivities.

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