Reverse asymmetric catalytic epoxidation of unfunctionalized alkenes
作者:Andreas Scheurer、Paul Mosset、Martina Spiegel、Rolf W. Saalfrank
DOI:10.1016/s0040-4020(98)01106-5
日期:1999.1
from tartaric-derived alicyclic C2 symmetric vicinal diamines were studied in the catalysis of the asymmetricepoxidation of unfunctionalized alkenes. Although the enantioselectivities obtained were not as high as for Jacobsen and Katsuki catalysts, the most striking result was the reversed asymmetric induction.
A new class of highly stable O,N,N,O-tetradentate bioxazolineligands were synthesized from l-tartaric acid. Exploration of those ligands in Pd-catalyzed asymmetric allylic alkylation yielded alkylated product up to 96% ee. Necessity of additional chelation to obtain high enantioselectivity was also demonstrated. Structural modifications of this ligand might result in identification of a novel privileged
Diazadioxadecalin and salen podands and macrocycles within dynamic combinatorial virtual libraries: structure, prototropy, complexation and enantioselective catalysis
作者:Alexander Star、Israel Goldberg、Benzion Fuchs
DOI:10.1016/s0022-328x(01)00882-8
日期:2001.7
which can be biased by complex formation with metal ions of different ionic radius. A rare instance of simultaneous occurrence of keto–enamine and phenol–imine tautomers in the solid state of 6 was unravelled (X-ray at two temperatures) and the strength of the intramolecular hydrogen bonding (and hence, the extent of ring closure) in 6 is temperature dependent. Compounds 6, 11 and 12–14 constitute
Efficient synthesis of (2R,3R)- and (2S,3S)-2,3-diaminobutane-1,4-diol and their dibenzyl ethers
作者:Andreas Scheurer、Paul Mosset、Rolf W Saalfrank
DOI:10.1016/s0957-4166(97)00086-4
日期:1997.4
(2R,3R)-2,3-Diaminobutane-1,4-diol 6 and its dibenzyl ether 7 were efficiently synthesized starting from L-tartaric acid 1a. The crucial step, debenzylation of intermediate dibenzyloxydiazide 4, was accomplished in good yield by boron trichloride-dimethyl sulfide complex. The enantiomeric series was similarly obtained starting from D-tartaric acid.
The Pd(III) oxidationstate is unusual and unstable since it strongly tends to disproportionate. We synthesized the quasi-one-dimensional (1D) halogen-bridged Pd(III)–Cl complex [Pd(dabdOH)2Cl]Cl2 (1-Cl; dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol) with multiple hydrogen bonds. From single-crystal X-ray diffraction, the bridging Cl− ions were located at the midpoint of the Pd–Cl–Pd moieties in the
Pd(III)的氧化态异常且不稳定,因为它极易发生歧化。我们合成了准一维(1D)卤素桥式Pd(III)-Cl络合物[Pd(dabdOH)2 Cl] Cl 2(1-Cl ; dabdOH =(2 S,3 S)-2,3-具有多个氢键的二氨基丁烷-1,4-二醇)。从单晶X射线衍射,桥接氯-离子定位在一支维链的Pd的氯-钯结构部分的中点,表明钯离子是在Pd(III)的平均化合价(AV)状态。此外,Pd(III)d z 2的亮点使用扫描隧道显微镜每5Å观察到Fermi能级以上Hubbard带的上部轨道。这些结果清楚地表明,Pd离子在1-Cl中处于Pd(III)AV状态。此外,迄今为止,在报告的一维Pd-Cl链中,1-Cl具有最高的热稳定性(470 K),在Pd(III)络合物中具有最高的电导率(在300 K时为0.6 S cm -1)。