The use of enantiomerically pure phosphine ligands in asymmetric catalysis is a popular strategy for asymmetric synthesis.[1] In Gilheany laboratory a simple, and cost-effective methodology has been developed in synthesizing enantioenriched tertiary P-stereogenic phosphines, phosphine boranes and phosphine oxides under both asymmetric Appel and reverse Appel reaction conditions.[2.3] Here, we have investigated the effects on the outcome of the reactions of the aryl substituents in aryl(methyl)phenylphosphine derivatives by measuring the diastereomeric excess of the intermediate diastereomeric alkoxyphosphonium salt (DAPS).Further, the DAPS could be stereospecifically reduced using LiBH4 to give scalemic phosphine borane directly. Achiral reduction of the precursor chlorophosphonium salt CPS using LiBH4 was also demonstrated.  It was found that the substitution at the ortho position strongly affects the degree of stereoselection. However, there was no variation of stereoselectivity with the electronic effects of the para substituents.   References: [1]       A. Grabulosa, Ed.; P-Stereogenic Ligands in Enantioselective Catalysis, Royal Society of Chemistry: Cambridge, UK, 2011 . [2]      K. V. Rajendran, L. Kennedy, D. G. Gilheany, Eur. J. Org. Chem. 2010 , 5642-5649. [3]      K. V. Rajendran, D. G. Gilheany, Chem. Commun. 2012 , 48, 10040-10042.

Achiral and stereoselective reductions of phosphine oxides using LiBH<sub>4</sub>: Effect of aryl substituent on outcome in arylmethylphenylphosphine cases

248th National Meeting (2014)

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Achiral and stereoselective reductions of phosphine oxides using LiBH4: Effect of aryl substituent on outcome in arylmethylphenylphosphine cases

Achiral and stereoselective reductions of phosphine oxides using LiBH₄: Effect of aryl substituent on outcome in arylmethylphenylphosphine cases