New Chiral Metal Cluster Systems for Catalytic Asymmetric Syntheses of Chiral Alcohols

The efficient chiral Ru3(CO)12 systems were prepared in situ from Ru3(CO)12 and various chiral diiminoor diamino-diphosphine tetradentate ligands. The systems have been used for the asymmetric transfer hydrogenation of propiophenone in 2-propanol, leading to 1-phenyl-1-propanol in a 98% yield and 96% e.e. The IR study suggests that the carbonyl hydride anion [HRu3(CO)11]^- most probably exists as a principal species under the reaction conditions. The high chiral efficiency may be due to the synergetic effect produced by the neighboring ruthenium atoms and a special chiral micro-environment involving the polydentate ligand and the Ru3 framework.     

Convenient Asymmetric Borane Reduction of Ketones Catalyzed by Simple Amino Alcohols and Corresponding Amino Acids

The catalytic enantioselective borane reduction of ketones is a well-studied theme1. Since the pioneering work of Corey2, a variety of good catalysts have been synthesized through further modification on simple amino alcohols and their corresponding amino acids,3,4 . But when simple amino alcohols were directly used in the reduction their catalytic efficiency was very low. For the first time Buono5 has reported through carefully chosen reaction condition the catalytic efficiency of a simple…     

烯丙醇化合物的不对称环氧化

本文报道了三个脂肪族烯丙醇化合物(1-3)的不对称环氧化反应。由反式烯丙醇2得到的反式烯丙醇环氧化合物2a的对映体过量大于由顺式烯丙醇1得到的环氧化合物1a的对映体过量。叔羟基二取代烯丙醇3经不对称环氧化生成的3a,其对映体过量只有4%。     

Convenient Syntheses for Selectively Isotopically Labelled Acrylonitriles

A convenient labscale synthesis of selectively, isotopically labelled acrylonitriles (1) from readily available and relatively inexpensive enriched starting materials is described.     

A Convenient Syntheses of some New Substituted Guanidines

The cyanamides of 2,6-dimethylaniline, N-methyl-α, β -naphthylamines, 2-methylpiperidine and indoline yielded their respective guanido derivatives on treatment with dry ammonia and their structures have been characterized through spectral studies.     

不饱和一元醇、乙酸酯和醛的合成

大多数鳞翅目昆虫性信息素是不饱和长碳链(C_(12)～C_(16))醇、乙酸酯或醛,双键位置一般在5、7、8、9、10和11位。它们的差别主     

A Convenient Synthesis Of Isopropyl Ethers from Secondary Alcohols

A convenient synthesis of isopropyl ethers from the corresponding secondary alcohols has been developed, involving acetate formation, conversion to the enol ether via an organotitanium reagent, and subsequent catalytic hydrogenation to the isopropyl ether.     

Asymmetric Syntheses Aided by Biocatalysts

This article summarizes the achievements of the authors‘ group in the area of biocatalyst-catalyzed organic reactions in recent 10 years. A strain of Geotrichum sp. obtained by screeninu is capable of stereoselectlvely reducing a number of carbonyl compounds. In many cases, the stermghemistry is complementary with that obtained by baker‘ s yeast. Therefore, this microorganism provides a useful pathway to the preparation of alcohol eompounds with specific configurations. On the other hand, a nmmber of plant sourees have been screened for oxynitrilases and the hydrocyanation reactions of various arylcarboxalde-hydes have been investigated.A“micro-aqueous reaction system“ was invented,by which a serles of novel optically active cyanohydrins were prepared.On this hasis,a high through-put comtimasous reaction system has been designed.This paper also deseribes examples of the syntheses of bio-active compounds by using the optieally active compounds obtained from the above mentioned catalytic reactions as precursors.     

Asymmetric Syntheses of Pharmaceutically Interesting Piperidines

Alkyl-3-hydroxyl piperidine is a structural unit found in numerous bioactive natural products, drugs and drug candidates. For example, (+)-L-733 060 (1)1 and (+)-CP-99, 994 (2)2 are selective and potent neurokinin substance P receptor antagonists, which have been shown to possess potent antiemetic activity; febrifugine (3)3 and isofebrifugine (4)3 are well-known candidates of antimalarial agents isolated from Chinese medicinal plants Dichroa febrifuga. The important bioactivities, common str…     

Convenient and Selective Acetylations of Phenols,Amines and Alcohols

Two convenient methods have been developed for selective acetylation. In method 1, phenols and amines are selectively acetylated in the presence of alcohols by acetic anhydride in a biphasic aqueous NaOH-isopropanol mixture. In method 2, alcoholic group is acetylated in the presence of amino functions using a strong acidic resin.     

A Convenient Method for the Conversion of Halides to Alcohols

The displacement of halides in unactivated primary bromides and iodides, allylic and benzylic primary and secondary bromides, and primary and secondary α-bromoketones by formate, using triethylammonium formate as the formylating agent, followed by acid or base catalyzed hydrolysis has been found to be an efficient method for the conversion of halides to alcohols.     

A Convenient Preparation of Benzylic Homopropargylic Alcohols Via Allenyllithium Reagents

Among the distinctive methods providing acetylenic functions^1-3 reactions employing anionic propargylic equivalents opposed to electrophilic species provide a potentially valuable route to propargylic derivatives^4-6. Their general applicability in synthetic processes, however, is frequently hampered by the tendency of such nucleophiles to produce troublesome mixtures of isomeric acetylenic and allenic products in moderate yields.     

Asymmetric Guerbet Reaction to Access Chiral Alcohols

The first example of an asymmetric Guerbet reaction has been developed. Using commercially available, classic Noyori Ru^II‐diamine‐diphosphine catalysts, well‐known in asymmetric hydrogenation, racemic secondary alcohols are shown to couple with primary alcohols in the presence of a base, affording new chiral alcohols with enantiomeric ratios of up to 99:1. Requiring no reducing agents, the protocol provides an easy, alternative route for the synthesis of chiral alcohols. Mechanistic studies reveal that the reaction proceeds via a Ru‐catalyzed asymmetric hydrogen autotransfer process in concert with a base‐promoted allylic alcohol isomerization.     

A Convenient Preparation of Symmetric and Asymmetric Trifluoromethylphosphines

Abstract

Chloro(diethylamino)trifluoromethylphosphine (1), easily prepared from 2 by the method of W. Volbach and I. Ruppert [l], reacts with Grignard compounds to yield 3; the latter can be converted by HCl into the corresponding chloroderivatives, which upon repeated treatment with Grignard reagent yield symmetric and asymmetric trifluoro-methylphosphines 4.     

Asymmetric Syntheses Promoted by Organoselenium Reagents

Using chiral nonracemic electrophilic-organoselenium-reagents-asymmetric alkoxy-, hydroxy-, azido- and amido-selenenylation of alkenes were effected with high diastereoselectivity. These reagents have also been employed in catalytic amounts to promote one-pot selenenylation-deselenenylation processes. The asymmetric cyclization of properly substituted alkenes diastereoselectively afforded lactons, tetrahydrofurans oxazolines, thiazolines, pyrrolidines, isoxazolidines, 1,2-oxazines, and cyclic nitrones. Enantiopure dioxane, morpholine, tetrahydrofuran, oxazolidin-2-one and aziridine derivatives were prepared from alkenes, PhSeX, and optically active nucleophiles or substrates.     

弱碱作用下从叔醇简便地合成烯烃

用甲磺酸酐和三乙胺作为脱水剂, 发展了一种从叔醇合成烯烃的简便方法, 反应时间短, 温和的条件和高产率使该方法可以快速地从叔醇合成烯烃.