Efficient, Rhodium‐Catalyzed Hydrogenation of α‐Dehydroamino Acid Esters with Chiral Monodentate Aminophosphanes Bearing Two Binaphthyl Groups

Abstract

Abstract All four stereoisomers of 4‐{4,5‐dihydro‐3 H ‐dinaphtho[2,1‐ c :1′,2′‐ e ]azepin‐4‐yl}dinaphtho[2,1‐ d :1′,2′‐ f ][1,3,2]dioxaphosphepine have been prepared from ( R or S )‐1,1′‐binaphthyl‐2,2′‐diyl chlorophosphite and the appropriate dinaphtho‐azepine. When reacted with [Rh(1,5‐cyclooctadiene) 2 ]BF 4 , highly active catalysts for the hydrogenation of α‐dehydroamino acid esters were obtained. The highest enantioselectivities (up to 99 % ee ) were achieved with the phosphoramidites having two chiral binaphthyl groups with opposite configurations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)