Studies on the Practical Synthesis of a New Type of Chiral Bisphosphines

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In this project, practical synthesis of chiral bis-phosphine ligands for asymmetric synthesis and development of a new type of chiral ligands were studied.(1) For putting chiral trans-bis-1,2-(diphenylphosphino)cyclobutane(DPCB), which we have recently developed, into practical use, we examined the reaction conditions such as base, solvent and temperature. The use of t-BuLi instead of n-BuLi as base improved the yield and purity of DPCB oxide. Asymmetric hydrosilylation of ketones using Rh(I)・ (+)- or (-)- DPCB complex was studied.(2) A new type of chiral phosphine ligands, 2-(diphenylphosphino)cycloalkylcarboxylic acids (abbreviated DPCAC) was synthesized. Each of chiral (+)- and (-)-DPCAC was successfully isolated by treatment of the racemic mixtrue of DPCAC with (+)- or (-)- phenylethylamine. Optically active DPCAC were effective as ligands for the palladiumcatalyzed asymmetric allylic alkylation of allyl acetates such as 1,3-diphenylprop-2-eny1 acetate and cyclohex-2-eny1 acetate with malonic acid esters and ethy1 diethylphosphono-acetate as soft carbon nucleophiles to give the alkylation products in good optical yields.