Inversion of configuration of α-trisubstituted(neopentyl) type secondary alcohols
摘要:
A variety of hindered alpha-trisubstituted optically active secondary alcohols has been converted into their enantiomers by treating the corresponding triflates with KNO2 in DMF in the presence of 18-crown-6 at room temperature.
Asymmetric Hydrosilylation of Ketones Using<b><i>Trans</i></b>-Chelating Chiral Peralkylbisphosphine Ligands Bearing Primary Alkyl Substituents on Phosphorus Atoms
作者:Ryoichi Kuwano、Masaya Sawamura、Junya Shirai、Masatoshi Takahashi、Yoshihiko Ito
DOI:10.1246/bcsj.73.485
日期:2000.2
Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001—0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)-secondary alcohols with up to 97% ee. The asymmetric
简单酮与二苯基硅烷的不对称氢化硅烷化在 -40 °C 下在铑配合物(0.001-0.01 摩尔量)存在下进行,该配合物与在磷原子上带有线性烷基取代基的反式螯合手性双膦配体(R,R) -(S,S)-Et-、Pr- 或 BuTRAP,得到相应的光学活性 (S)-仲醇,其 ee 高达 97%。使用具有更大 P 取代基的 TRAP 配体的不对称氢化硅烷化导致低得多的对映选择性。EtTRAP-铑催化剂对于具有铑原子配位位点的酮酯的不对称氢化硅烷化也有效(高达 98% ee)。通过使用 2.5 摩尔二苯基硅烷的不对称还原,从相应的二酮中获得了高达 99% ee 的旋光对称二醇。
Asymmetric Hydrogenation of <i>tert</i>-Alkyl Ketones
作者:Takeshi Ohkuma、Christian A. Sandoval、Rajagopal Srinivasan、Quinghong Lin、Yinmao Wei、Kilian Muñiz、Ryoji Noyori
DOI:10.1021/ja052071+
日期:2005.6.1
A combined system of RuCl2(tolbinap)(pica) and an alkaline or organic phosphazene base catalyzes asymmetric hydrogenation of sterically congested tert-alkyl ketones (TolBINAP = 2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl, PICA = alpha-picolylamine). Hydrogenation with RuH(eta1-BH4)(tolbinap)(pica) does not require any strong base. Alcoholic solvents strongly affect the catalytic efficiency. The reaction proceeds smoothly in ethanol under 1-20 atm of H2 and at room temperature with a substrate to catalyst molar ratio of up to 100 000. Various aliphatic, aromatic, heteroaromatic, and olefinic tert-alkyl ketones are convertible to the corresponding chiral carbinols in high enantiomeric purity. Olefinic and heteroaromatic functions are left intact. Certain cyclic ketones are also usable. The mode of enantioface selection is consistent and predictable.
Chiral synthesis via organoboranes. 14. Selective reductions. 41. Diisopinocampheylchloroborane, an exceptionally efficient chiral reducing agent
作者:Herbert C. Brown、J. Chandrasekharan、P. V. Ramachandran
DOI:10.1021/ja00213a030
日期:1988.3
Yatagai, Masanobu; Ohnuki, Takashi, Journal of the Chemical Society. Perkin transactions I, 1990, # 6, p. 1826 - 1828
作者:Yatagai, Masanobu、Ohnuki, Takashi
DOI:——
日期:——
Asymmetric Hydrosilylation of Symmetrical Diketones Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP