Parallel and Modular Synthesis of P-Chirogenic <i>P,O</i>-Ligands
作者:Magnus J. Johansson、Susanne Berglund、Yinjun Hu、Kristian H. O. Andersson、Nina Kann
DOI:10.1021/co2002119
日期:2012.5.14
A modular synthesis of P-chirogenic α-alkoxyphosphine ligands has been developed, allowing for the variation of two of the three groups on phosphorus. Oxidation and concomitant desymmetrization of a prochiral alkyl- or aryldimethylphosphine borane afforded α-hydroxyphosphines, which were subsequently deprotonated and alkylated in a parallel fashion. The choice of base and temperature for the alkylation
P-Chirogenic phosphine/sulfide hybrid ligands 1 were prepared by the use of optically active phosphine-boranes as the intermediates. The palladium complexes of the ligands exhibited high catalytic activity and enantioselectivity in allylic alkylation of 1-acetoxy-1,3-diphenylprop-2-ene with malonate esters.
Reduction of Functionalized Tertiary Phosphine Oxides with BH<sub>3</sub>
作者:Sylwia Sowa、Marek Stankevič、Anna Szmigielska、Hanna Małuszyńska、Anna E. Kozioł、K. Michał Pietrusiewicz
DOI:10.1021/jo502623g
日期:2015.2.6
A direct stereoselective conversion of tertiary hydroxyalkylphosphine oxides to the corresponding tertiary hydroxyalkylphosphineboranes 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 center dot center dot center dot B complexation directed by proximal alpha- or beta-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.
H-Adamantylphosphinates as Universal Precursors of P-Stereogenic Compounds
A new family of H-adamantylphosphinates as universal precursors of P-stereogenic ligands was obtained in one step from commercial chlorophosphines. Both enantiomers of these air- and moisture-stable intermediates can easily be separated by semipreparative chiral HPLC on a gram scale and individually undergo stereoselective transformations to afford each enantiomer of a set of P-stereogenic compounds such as secondary phosphine oxides and boron-protected monophosphines.
Stereoselective, Oxidative One-Carbon Degradation of Alkyl(dimethyl)phosphine-Boranes. Synthesis of Enantiomerically Enriched Secondary Phosphine-Boranes