Early Transition Metal Alkoxide Complexes Bearing Homochiral Trialkanolamine Ligands
摘要:
Enantiomerically pure trialkanolamines of the formula N(CH(2)CHROH)(3), where R = methyl (3a), cyclohexyl (3b), tert-butyl (3c), or phenyl (3d), are readily synthesized by the reaction of ammonia with 3 equiv of an enantiopure epoxide. Trialkanolamines 3a-d replace n-propanol in tri-n-propyl vanadate to afford corresponding complexes 4a-d of the formula LV=O, where L is the deprotonated trialkanolamine. Similarly, (S,S,S)-triisopropanolamine 3a reacts with Ti((OPr)-Pr-i)(4) to produce monomeric LTi((OPr)-Pr-i), 7a, which upon treatment with acetyl chloride gives the chloro complex LTiCl, 7b. The later group 5 ethoxides react with 3a to produce LM(OEt)(2) (M = Nb, Ta). Partial hydrolysis of the Nb and Ta derivatives produces tetrameric mu-oxo-bridged structures which retain the trialkanolamine ligands. In all complexes the transition metal resides in a highly asymmetric environment, suggesting that this class of complexes may find use in the field of asymmetric catalysis. The X-ray crystal structures of complexes 4c and 7b are reported.
A catalytic enantioselective synthesis of chiral monosubstituted oxiranes
摘要:
A new catalytic enantioselective synthesis of monosubstituted oxiranes has been developed from achiral trichloromethyl ketones by (a) enantioselective carbonyl reduction, (b) selective bis-dechlorination and (c) base-induced ring closure of the resulting chlorohydrins.
Development of a general copper-catalyzed vinylic Finkelstein reaction—application to the synthesis of the C1–C9 fragment of laingolide B
作者:Antoine Nitelet、Kévin Jouvin、Gwilherm Evano
DOI:10.1016/j.tet.2016.07.018
日期:2016.10
conditions compatible with a range of highly functionalized substrates. The potential of this vinylic halogen exchange reaction in total synthesis and medicinal chemistry was demonstrated by its successful use for the synthesis of the C1–C9 fragment of laingolide B and for the late-stage modification of drug-like molecules. The extension of this halogen exchange to the acetylenic and allenic Finkelstein
Highly Selective Hydrolytic Kinetic Resolution of Terminal Epoxides Catalyzed by Chiral (salen)Co<sup>III</sup> Complexes. Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols
作者:Scott E. Schaus、Bridget D. Brandes、Jay F. Larrow、Makoto Tokunaga、Karl B. Hansen、Alexandra E. Gould、Michael E. Furrow、Eric N. Jacobsen
DOI:10.1021/ja016737l
日期:2002.2.1
The hydrolytickineticresolution (HKR) of terminal epoxides catalyzed by chiral (salen)Co(III) complex 1 x OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several
Hydrolytic Kinetic Resolution of Epoxides Catalyzed by Chromium(III)-endo,endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] Complexes. Improved Activity, Low Catalyst Loading
作者:Albrecht Berkessel、Erkan Ertürk
DOI:10.1002/adsc.200606181
日期:2006.12
The hydrolytickineticresolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane), was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol %) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99 %
Asymmetric synthesis using chirally modified borohydrides. Part 3. Enantioselective reduction of ketones and oxime ethers with reagents prepared from borane and chiral amino alcohols
The asymmetric reduction of aromatic and aliphatic ketones, halogeno ketones, hydroxy ketones, keto esters, and ketone oxime ethers with reagents prepared from borane and chiral amino alcohols has been investigated. When α,α-diphenyl β-amino alcohols, such as (2S,3R)-(–)-2-amino-3-methyl-1,1 -diphenylpentanol (2d), were used as a chiral auxiliary, very high enantioselectivities (ca. 90 % e.e.) were
Modular Monodentate Oxaphospholane Ligands: Utility in Highly Efficient and Enantioselective 1,4-Diboration of 1,3-Dienes
作者:Christopher H. Schuster、Bo Li、James P. Morken
DOI:10.1002/anie.201102404
日期:2011.8.16
Tune it up! Tunable, chiral, monodentateoxaphospholaneligands (termed OxaPhos) are highly effective in the Pt‐catalyzed title reaction, providing the 1,4‐addition products in enantiomer ratios approaching 99:1 (see scheme). In the presence of enantiomerically pure cis‐iBu‐OxaPhos, a catalyst loading of only 0.02 mol % [Pt(dba)3] was sufficient for effective reaction. pin=pinacolato, dba=dibenzylideneacetone