Transfer of chirality from ligands to metal centers: recent examples

Recent examples of "chiral at metal" complexes and assemblies that are produced by chirality transfer of information from enantiopure ligands to metal ions are reported. They highlight the new progress that has been made in this area in the last two years and the new tendencies that such a topic is following. Besides the fundamental aspects related to the stereoselective synthesis of chiral complexes, the progress in diverse classes of chiral complexes for applications in materials science (chiral switches and molecular machines, biological mimics, CPL probes, etc.) is reported.     

Cyanosilylation of Prochiral Ketones Catalyzed by Lanthanide Complexes

A new series of silylene‐bridged rare‐earth complexes involving fluorenyl are shown to be the very efficient Lewis acid catalysts, giving some cyano trimethylsilyl ethers of ketones in >99% yields.     

潜手性Schiff碱不对称催化还原反应研究进展

对近年来潜手性Schiff碱的不对称催化氢化的发展状况按照均相、非均相及氢转移催化氢化三种类型进行了较为详尽的综述.     

Recent Advances in Enantioselective Desymmetrizations of Prochiral Oxetanes

Strain relief of oxetanes offers a plethora of opportunities for the synthesis of chiral alcohols and ethers. In this context, enantioselective desymmetrization has been identified as a powerful tool to construct molecular complexity and this has led to the development of elegant strategies on the basis of transition metal, Lewis acid, and Brønsted acid catalysis. This review highlights recent examples that harness the inherent reactivity of prochiral oxetanes and offers an outlook on the immense possibilities for synthetic application.     

Prochiral and chiral resolution in 2H NMR spectra: solutes in stretched and compressed gelatin gels

We demonstrate prochiral and chiral spectral resolution using residual (2)H NMR quadrupolar splittings over a wide range of anisotropic conditions in liquid samples. We use a reversible gel-stretching/compressing device in a conventional high-field NMR spectrometer. We show the stability of gelatin gels as well as their unique ability to switch between multiple stretched and compressed states, thus also changing the sign of residual dipolar couplings in (1)H and (13)C NMR. This flexibility will be important for resolving spectra of mixtures of other chiral compounds and for structure determination of selected peptides.     

Synthesis of N-Squaramidoacids and Their Application in Asymmetric Borane Reduction of Prochiral Ketones

A series of novel N-squaramidoacid ligands were prepared conveniently. Without converting to corresponding amino alcohols, these ligands could be used in asymmetric borane reduction of prochiral aromatic ketones to give secondary alcohols in good to excellent enantiomeric excesses. The results showed that N-squaramidoacids are more efficient ligands than N-sulfonyl amino acids. N-Squaryl proline was proved to be an excellent ligand in this catalytic asymmetric process.     

雪松胺醇-硼烷络合物催化的潜手性酮的不对称还原反应

雪松胺醇-硼烷络合物催化的潜手性酮的不对称还原反应     

二苯基脯氨醇及其衍生物对前手性酮的不对称催化还原研究进展

对(S)-α,α-二苯基脯氨醇及其衍生物对前手性酮的不对称催化还原研究进行了综述, 表明它们具有催化还原产率高、对映选择性好的作用, 是一类性能优秀的不对称还原反应的有机小分子催化剂.     

Synthesis of Bis—N—squaramidoacids and their Applications to Asymmetric Reduction of Prochiral Ketone and Diketones

A series of novel bis-squaramidoacid ligands were prepared. Prochiral ketone and diketones were direct reduced by borane in the presence of these ligands giving secondary alcohol products with enantiomeric excesses up to 64.2% for ω-bromoacetophenone and 90.0% for 1,6-diphenyl- 1, 6-hexanedione.     

Highly Enantioselective Adsorption of Small Prochiral Molecules on a Chiral Intermetallic Compound

Intrinsically chiral surfaces of intermetallic compounds are shown to be novel materials for enantioselective processes. Their advantage is the significantly higher thermal and chemical stability, and therefore their extended application range for catalyzed chiral reactions compared to surfaces templated with chiral molecular modifiers or auxiliaries. On the Pd₁‐terminated PdGa(111) surface, room‐temperature adsorption of a small prochiral molecule (9‐ethynylphenanthrene) leads to exceptionally high enantiomeric excess ratios of up to 98 %. Our findings highlight the great potential of intrinsically chiral intermetallic compounds for the development of novel, enantioselective catalysts that can be operated at high temperatures and potentially also in harsh chemical environments.     

Catalytic Enantioselective Reduction of Prochiral Ketones with Chiral Ferrocenyl Amino Alcohols

The asymmetric reduction of prochiral ketones was catalyzed by a class of recoverable and highly stable chiral ferrocenyl amino alcohols derived from natural amino acids to yield optically active secondary alcohols in high chemical yields and moderate to good enantiomeric excesses.     

Stereochemical Studies of Chiral Acyclic Nitroxides Coupling with a Prochiral Radical

Abstract

A series of acyclic chiral nitroxides bearing a hydrogen atom on the carbon adjacent to the nitroxide nitrogen was investigated for stereoselectivity in a coupling reaction with the prochiral radical 1‐phenethyl. In one case, an x‐ray structure of the major diastereomer was obtained, which corroborates a model for predicting the stereoselectivity.     

手性氨基醇催化的前手性芳酮的不对称还原反应

首次以天然D-樟脑的衍生物为原料, 合成了两个新型龙脑基氨基醇配体, 研究了它们与硼烷原位制备成手性噁唑硼烷后, 在不对称催化氢化还原前手性芳酮中的性能, 得到的手性仲醇的对映体过量(ee)值最高可达96%, 还考察了反应温度、时间、溶剂等因素对苯乙酮的不对称氢化还原的化学产率和光学收率的影响.