Catalytic asymmetric hydrocyanation of a,b-unsaturated ketones into the corresponding chiral b-cyano ketones is a challenging scientific endeavor. Four major hurdles must be cleared before this reaction can be realized: 1) use of HCN as a cyanide source, [1] 2) high 1,4-addition selectivity over 1,2-addition, 3) sufficient enantioface selectivity and, 4) high catalytic activity (low catalyst loading). Recently, Shibasaki and co-workers reported pioneering studies on asymmetric 1,4-addition of cyanide to the conjugate enones catalyzed by chiral Gd and Sr compounds. [2][3][4][5] A wide range of 1,4-adducts were obtained in high enantiomeric excess (ee), but two equivalents of a tert-C 4 H 9 (CH 3 ) 2 SiCN/2,6-dimethylphenol system were required as a cyanide source to achieve the best catalyst performance.[6] Furthermore, the substrate-tocatalyst molar ratio (S/C) of 10-200 in these reactions was relatively low. [2] Our research group recently reported the asymmetric cyanation of aldehydes and a-keto esters catalyzed by our original [Ru(phgly) 2 (binap)]/Li salt systems. [7,8] The corresponding cyanated products were obtained in high ee. The spectroscopic analysis suggested that the bimetallic species [Li·Ru(phgly) 2 (binap)]+ acted as a chiral Lewis acidic catalyst. Herein, we describe the efficient asymmetric conjugate addition of HCN to a,b-unsaturated ketones catalyzed by the combined system of [Ru(phgly) 2 (binap)] and C 6 H 5 OLi. The reaction was carried out with an S/C of 200-1000 at À20-0 8C to afford the b-cyano ketones in up to 98 % ee.
Asymmetric conjugate hydrocyanation of α,β-unsaturated carboxylic acid derivatives catalyzed by a Ru[(S)-phgly]2[(S)-binap]-CH3OLi system was examined. The N-acylpyrrole gave the best result in terms of reactivity and enantioselectivity. A series of substrates with alkyl or heterosubstituted alkyl groups at the β-position reacted with a substrate-to-catalyst molar ratio of 200-2000 to afford the β-cyano products in the range of 88%->99% ee. The mode of enantioselection in the hydrocyanation was proposed.
Catalytic asymmetric hydrocyanation of a,b-unsaturated ketones into the corresponding chiral b-cyano ketones is a challenging scientific endeavor. Four major hurdles must be cleared before this reaction can be realized: 1) use of HCN as a cyanide source, [1] 2) high 1,4-addition selectivity over 1,2addition, 3) sufficient enantioface selectivity and, 4) high catalytic activity (low catalyst loading). Recently, Shibasaki and co-workers reported pioneering studies on asymmetric 1,4-addition of cyanide to the conjugate enones catalyzed by chiral Gd and Sr compounds. [2][3][4][5] A wide range of 1,4-adducts were obtained in high enantiomeric excess (ee), but two equivalents of a tert-C 4 H 9 (CH 3 ) 2 SiCN/2,6-dimethylphenol system were required as a cyanide source to achieve the best catalyst performance. [6] Furthermore, the substrate-tocatalyst molar ratio (S/C) of 10-200 in these reactions was relatively low. [2] Our research group recently reported the asymmetric cyanation of aldehydes and a-keto esters catalyzed by our original [Ru(phgly) 2 (binap)]/Li salt systems. [7,8] The corresponding cyanated products were obtained in high ee. The spectroscopic analysis suggested that the bimetallic species [Li·Ru(phgly) 2 (binap)] + acted as a chiral Lewis acidic catalyst. Herein, we describe the efficient asymmetric conjugate addition of HCN to a,b-unsaturated ketones catalyzed by the combined system of [Ru(phgly) 2 (binap)] and C 6 H 5 OLi. The reaction was carried out with an S/C of 200-1000 at À20-0 8C to afford the b-cyano ketones in up to 98 % ee.
Asymmetric cyanosilylation of alkynyl ketones with the catalyst systems consisting of amino acid/2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP)/ruthenium(II) complex and lithium phenoxide (Ru⋅Li cat.) was studied. The reaction was conducted in tert‐butyl methyl ether (TBME) at −78 °C with a substrate‐to‐catalyst molar ratio (S/C) as high as 2000. A series of simple and functionalized ketones was converted into the alkynyl tertiary cyanohydrin derivatives in up to 99% ee. Appropriate selection of an amino‐acid ligand of the catalyst according to the substrate structure was crucially important to achieve high enantioselectivity and a wide scope of substrates. Transformation of the chiral cyanohydrin product into a functionalized lactone was also examined.magnified image
A lightweight human phantom material that has a specific gravity below 1.0 is newly developed and a full sized realistic shaped human phantom model is constructed using this material.Fundamental material composites are carbon nanotubes and silicone rubber. The carbon nanotubes enable this material to simulate various biological tissues with less specific gravity values than those of original ones. In addition, using the silicone rubber allows us to construct phantom models of various shapes. This paper describes the design principle and estimates the relation between complex permittivity and composition ratio of the material experimentally. Finally, a full sized realistic shaped human phantom model is constructed to show the features of the proposed material.
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