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  • Title: Conformational preferences and enantiodiscrimination of phosphino-4-(1-hydroxyalkyl)oxazoline-metal-olefin complexes resulting from an OH-metal hydrogen bond.
    Author: Frölander A, Lutsenko S, Privalov T, Moberg C.
    Journal: J Org Chem; 2005 Nov 25; 70(24):9882-91. PubMed ID: 16292819.
    Abstract:
    [reaction: see text] Phosphinooxazolines carrying (1-hydroxy-1-phenyl)methyl and (1-methoxy-1-phenyl)methyl substituents in the 4 position of the oxazoline ring exhibit contrasting behavior in Pd- and Ir-catalyzed allylic alkylations. Whereas catalysts with the methoxy-containing ligand generally provide products with high ee's, use of catalysts prepared from the hydroxy-containing ligand results in products with low ee's or even racemates. DFT calculations suggest the presence of a hydrogen bond with Pd(0) as the proton acceptor in the hydroxy-containing olefin-Pd(0) complexes, which induces a conformational change in the ligand, leading to different stereoselectivity.
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