A stable and easily prepared catalyst for the enantioselective reduction of ketones. Applications to multistep syntheses
作者:E. J. Corey、Raman K. Bakshi、Saizo Shibata、Chung Pin Chen、Vinod K. Singh
DOI:10.1021/ja00259a075
日期:1987.12
recently described a new method for the catalytic enantioselectivereduction of ketones to chiral secondary alcohols.' The stoichiometric reagent in the reduction is borane (usually 0.6 molfmol of ketone), and the catalyst is a chiral oxazaborolidine such as 1 (0.05-0.1 molfmol of ketone). Excellent enantioselectivities, easy recoverability of the chiral catalyst predecessor, near quantitative yields, short
The asymmetric reduction of aromaticketones was catalyzed by a class of recoverable and highly stable chiral sulfonamides derived from (S)-proline to yield optically active secondary alcohols in high yields and with enantiomeric excesses of up to 91%.
Cyclic ethers have been effectively synthesized via the intramolecular cyclization of diols using trimethyl phosphate and NaH. The present cyclization could proceed at room temperature to produce 5–7 membered cyclic ethers in good to excellent yields. Substrates possessing a chiral secondary hydroxy group were transformed into the corresponding chiral cyclic ethers along with the retention of their
Brønsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
作者:Anon Bunrit、Christian Dahlstrand、Sandra K. Olsson、Pemikar Srifa、Genping Huang、Andreas Orthaber、Per J. R. Sjöberg、Srijit Biswas、Fahmi Himo、Joseph S. M. Samec
DOI:10.1021/jacs.5b02013
日期:2015.4.15
intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as
富含对映体的苄基、炔丙基、烯丙基和烷基醇的羟基已被不带电荷的 O-、N-和 S 中心亲核试剂在分子内置换,在次膦酸催化下产生富含对映体的四氢呋喃、吡咯烷和四氢噻吩衍生物。五元杂环产物的产率很高,手性转移程度高,水是唯一的副产物。消旋化实验表明次膦酸不会促进 SN1 反应性。密度泛函理论计算证实了一种反应途径,其中次膦酸在分子内取代反应中充当双功能催化剂。在该机制中,次膦酸的酸质子使羟基质子化,从而增强离去基团能力。同时地,次膦酸的氧代基团作为碱提取亲核质子,从而增强亲核性。该反应将开辟新的原子高效技术,使醇在未来能够在取代反应中用作核离剂。
Asymmetric Catalytic Reduction of Ketones with Hypervalent Trialkoxysilanes
作者:R. Schiffers、H. Kagan
DOI:10.1055/s-1997-982
日期:1997.10
The catalytic asymmetric reduction of different ketones1 with transient hypervalent silicon hydrides is described. Trialkoxysilanes, upon activation by a small amount of a chiral nucleophile, underwent addition to the carbonyl group, forming the corresponding silyl protected alcohols, which were cleaved during the workup to give the enantiomerically enriched product alcohols. A brief screening of the