A direct stereoselective conversion of tertiary hydroxyalkylphosphine oxides to the corresponding tertiary hydroxyalkylphosphine-boranes involving facile reduction of the P═O bond by BH3 under mild conditions has been developed. The unprecedented facility of reduction of the strong P═O bond by BH3, a mild reducing agent, has been achieved through an intramolecular P═O···B complexation directed by proximal α- or β-hydroxy groups present in the phosphine oxide structures. As established by two chemical correlations, the developed transformation of hydroxyalkylphosphine oxides into hydroxyalkylphosphine-boranes takes place with complete inversion of configuration at P.

Vinylphosphane oxides 6 undergo catalytic olefin homo-metathesis leading to achiral and P-stereogenic diphosphane dioxides 7 with exclusive (E)-selectivity. Similarly, EWG-substituted vinylphosphane oxides 11, 12 could be prepared with complete (E)-olefin selectivity via olefin cross-metathesis with electron-deficient substrates, such as methyl acrylate and 2-fluorostyrene, using nitro-Hoveyda ruthenium precatalyst III. Cross-and homo-metathesis of chiral non-racemic vinylphosphane oxides proceeds without racemization of the phosphorus center of chirality.

Six secondary phosphine oxides and their tautomeric equilibria as free ligands and in the presence of an equimolar amount of the chiral dirhodium complex Rh* are described and discussed. Discrimination of enantiomers is easily possible by inspecting the (31)P NMR resonances; some (1)H and (13)C NMR resonances are useful as well. H/D exchange of the acidic protons in the phosphine oxides takes place with acetone-d(6), the solvent additive, after some hours but does not obscure the chiral recognition experiment. (103)Rh,(31)P coupling constants are discussed briefly. Decomposition of ligand molecules in 1:1-Rh*-adducts occurs slowly but completely.

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The symmetrical bis(phosphane oxide) 1 and its chiral derivatives 2 and 3 form a variety of adduct species with the dirhodium complex [Rh−Rh] which can be identified by low-temperature 1 H and 31 P NMR spectroscopy by using varying [Rh−Rh]:ligand ratios. The asymmetric bis(phosphane oxide) 3 shows a distinct preference for binding through the Ph 2 P= O (P a ) as compared to the tBu(Ph)P=O (P b ) functionality due to the bulky tert-butyl group. The chiral bis(phosphane ox-