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.     

新型手性β—氨基醇用于不对称催化醛类烷基化反应

将自己研制的一种新型β－氨基醇作为手性源用于醛类的不对称催化烷基化反应。考察了在这种手性β－氨基醇存在时各种醛和二乙基锌作用生成相应的手性仲醇的光学收率，考察了几种反应条件参数对于苯甲醛的这种不对称催化反应的影响，其中最佳结果为１－苯基丙醇的光学收率达７４．１％，而其化学产率达９３．８％。     

新型手性β－氨基醇用于不对称催化醛类烷基化反应

将自己研制的一种新型β－氨基醇（Ⅰ）作为手性源用于醛类的不对称催化烷基化反应。考察了在这种手性β－氨基醇（催化量）存在时各种醛和二乙基锌作用生成相应的手性仲醇的光学收率。考察了几种反应条件参数对于苯甲醛的这种不对称催化反应的影响，其中最佳结果为１－苯基丙醇的光学收率达７４．１％，而其化学产率达９３．８％。     

新型手性基醇的合成及其用于不对称催化醛类烷基化反应

制备了一种由糖类化合物衍生物新型手性氨基醇（Ｉ），并将其作为手性源用于醛类的不对称烷基化反应，考察了在手性氨基酸的存在下，各种醛和二乙基锌作用生成相应的手性仲醇的光学收率及化学收率，结果表明，该催化剂地于芳香醛的烷基化更为有效，并考察了几种反应条件对于苯甲醛的不对称催化烷基化反应的影响，其中最佳结果为１－苯基－１－两醇的光学收率达８２．７％，而化学收率达５８．８％。     

新型手性氨基醇的合成及其用于不对称催化醛类烷基化反应

制备了一种由糖类化合物衍生的新型手性氨基醇（Ⅰ），并将其作为手性源用于醛类的不对称烷基化反应．考察了在手性氨基醇的存在下，各种醛和二乙基锌作用生成相应的手性仲醇的光学收率及化学收率．结果表明，该催化剂对于芳香醛的烷基化更为有效．并考察了几种反应条件对于苯甲醛的不对称催化烷基化反应的影响，其中最佳结果为１－苯基－１－丙醇的光学收率达８２．７％，而化学收率达５８．８％．     

重氮化合物与醇的插入反应合成α-烷氧基-β-二羰基化合物

研究了在过渡金属配合物催化下α-重氮-β-二羰基化合物与醇的插入反应, 考察了重氮化合物的结构、醇的结构、催化剂的性质、反应溶剂和反应温度对这一反应的影响. 发现当重氮化合物与甲醇的物质的量比为1∶10, 1 mmol% Rh₂(OAc)₄为催化剂和回流的苯的条件下, 反应能够以高的化学产率生成α-甲氧基-β-二羰基化合物. 手性醇衍生的重氮乙酰乙酸酯反应的产物中两种非对应异构体的比例为3∶2～1∶1.     

Oxone/CaCl2/TEMPO体系在温和条件下对醇的氧化反应

Oxone/TEMPO/CaCl₂ (TEMPO＝2,2,6,6-Tetramethyl-1-piperidinyloxy)是一种稳定安全和易得的氧化催化体系, 在室温条件下, 可以氧化苄基或烷基醇生成醛或酮. 苄基伯醇很容易被氧化成相应的醛, 有较高的反应收率(90%～96%), 仲醇氧化成相应的酮, 收率在81%～85%之间, 1,4-丁二醇环氧化生成γ-丁内酯得到了94%的收率.     

(S)-和(R)-盐酸氟西汀的不对称合成

盐酸氟西汀是一种临床广泛使用的非三环类抗抑郁药, 本工作介绍了一种不对称合成(S)-和(R)-盐酸氟西汀的方法. 以自制的手性噁唑硼烷为催化剂, 将起始原料β-氯苯丙酮不对称催化氢化还原成(S)-或(R)-手性醇, 这一步的化学收率和光学收率都较高. 然后再经两步, (S)-和(R)-手性醇转化为(S)-和(R)-盐酸氟西汀. 整个工艺只需三步, 总收率为66.5%, 盐酸氟西汀对映体的ee值可达98.6%. 还考察了反应温度、溶剂、催化剂的量等因素对β-氯苯丙酮的不对称氢化还原的化学产率和光学收率的影响.     

磺氨基醇手性配体的合成及钛配合物催化二乙基锌对醛的不对称加成反应

合成了手性磺氨基醇配体3～5, 将这些配体和Ti(O-i-Pr)₄应用于二乙基锌对醛的不对称加成反应, 获得了好的对映选择性, ee值最高为91%.     

氰化钠和醛及苦杏仁粗酶一锅法合成手性氰醇

直接使用固体氰化钠代替易挥发的HCN为氰源,用来源于苦杏仁的(R)-醇腈酶粗酶催化和醛的反应,并加入足量的HOAc来抑制非酶促反应和手性氰醇产物的外消旋化,一锅法合成了手性氰醇.考察了酸、(R)-醇腈酶粗酶、水、氰化钠和反应温度等因素对反应的影响.大部分反应底物的产物的产率及ee值都大于95%.该方法简单、安全、低成本、高对映选择性和收率,具有很好的应用价值.     

Use of native and derivatized cyclodextrin chiral stationary phases for the enantioseparation of aromatic and aliphatic sulfoxides by high performance liquid chromatography

Summary The enantioselectivity of native and derivatized cyclodextrin stationary phases for aromatic and aliphatic chiral sulfoxides was evaluated using high performance liquid chromatography (HPLC). Many sulfoxide enantiomers could be baseline resolved using the derivatized cyclodextrin stationary phases in the reverse phase mode. The most important factor influencing enantioselectivity is the presence of steric bulk alpha to the chiral center. However, substituents on an aromatic ring bonded to the sulfoxide have less pronounced effects on enantioselectivity. The 2,3-dimethyl β-cyclodextrin exhibits the broadest anantioselectivity for neutral chiral sulfoxides. Native cyclodextrins and hydroxypropyl-β-cyclodextrins were much less effective in separating this class of molecules. The hydrogen bonding ability of the organic modifier does not significantly affect enantioselectivity.     

Core-shell structured mesoporous silica: a new immobilized strategy for rhodium catalyzed asymmetric transfer hydrogenation

A core-shell structured heterogeneous rhodium catalyst exhibited excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, which could be recovered easily and used repetitively twelve times without affecting obviously its enantioselectivity.     

Magnetically recoverable SiO2-coated Fe3O4 nanoparticles: a new platform for asymmetric transfer hydrogenation of aromatic ketones in aqueous medium

A magnetically recoverable chiral rhodium catalyst exhibited excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, which could be recovered easily via a small magnet and used repetitively ten times without obviously affecting its enantioselectivity.     

Recoverable organorhodium-functionalized polyhedral oligomeric silsesquioxane: a bifunctional heterogeneous catalyst for asymmetric transfer hydrogenation of aromatic ketones in aqueous medium

A bifuctional heterogeneous chiral rhodium catalyst exhibited excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation of aromatic ketones and their analogues in aqueous medium, which could be recovered easily and used repetitively without affecting obviously its enantioselectivity.     

Evolution of chiral Lewis basic N-formamide as highly effective organocatalyst for asymmetric reduction of both ketones and ketimines with an unprecedented substrate scope

L-Pipecolinic acid derived Lewis basic N-formamide has been developed as a first highly effective catalyst for the asymmetric reduction of aromatic and aliphatic ketones as well as aromatic and aliphatic ketimines in good to high enantioselectivity.     

Organocatalytic asymmetric synthesis of alpha,alpha-disubstituted alpha-amino acids and derivatives

It is shown that racemic oxazolones are excellent reagents for the synthesis of chiral quaternary amino acids and its derivatives by the diastereo- and enantioselective nucleophilic addition to alpha,beta-unsaturated aldehydes catalyzed by diarylprolinol silyl ethers. The scope of this new organocatalytic reaction is demonstrated for different oxazolones having aromatic and alkyl groups at the reactive carbon atom and different aromatic and aliphatic substituted alpha,beta-unsaturated aldehydes, for which the stereoselective reaction proceeds with good yield, moderate to good to very high diastereoselectivity, and very high enantioselectivity. The potential of the reaction is shown for the synthesis of optically active alpha,alpha-disubstituted alpha-amino acids, alpha-quaternary proline derivatives, amino alcohols, lactams, and tetrahydropyranes. Furthermore, we have calculated by DFT-methods the transition-state structures that account for both the diastereo- and enantioselectivity observed for the addition of oxazolones to the alpha,beta-unsaturated aldehydes. For one class of compounds, the stereoselectivity is controlled by a hydrogen-bonding interaction of the enolate-form of the oxazolone with an ortho-hydroxy-phenyl substituent of the alpha,beta-unsaturated aldehyde, whereas the benzhydryl-protecting group in the oxazolone determines the diastereo- and enantioselectivity in a more general manner for both aromatic and aliphatic alpha,beta-unsaturated aldehydes.     

A comparative study of the asymmetric epoxidation of aromatic olefins using the first generation manganese salen epoxidation catalysts and their light fluorous variants: an interesting discovery on the use of benzotrifluoride as a cosolvent

The asymmetric epoxidation of aromatic olefins using optically active first generation manganese salen catalysts and light fluorous variants was examined. Although a slight decrease in the enantioselectivity of the product was observed when light fluorous catalysts were employed, the activities of these catalysts were higher than those of the non-fluorous catalysts. Additionally the influence on enantioselectivity of the oxidation was examined when fluorous cosolvents were used. The enantioselectivity of the oxidation increased with the addition of benzotrifluoride (BTF) regardless of whether a fluorous or non-fluorous salen catalyst was used.     

Tertiary pentyl groups enhance salen titanium catalyst for highly enantioselective trimethylsilylcyanation of aldehydes

tert-Pentyl groups are recognized to be highly effective steric groups that can enhance enantioselectivity of salen titanium complexes when they are used in asymmetrical cyanation of aromatic aldehydes. High ee (92-97%) has been obtained with several aldehyde substrates. Compared to its tert-butyl analogue, the tert-pentyl group has been found to improve enantioselectivity and in some cases quite dramatically.     

Enantioselective vinylogous aldol reaction of Chan’s diene catalyzed by hydrogen-bonding

Hydrogen-bonding activation of aromatic aldehydes by a TADDOL-derivative promotes the vinylogous aldol reaction of Chan’s diene in moderate efficiency and enantioselectivity. Electron-poor aromatic aldehydes show an enhanced reactivity and a competing asymmetric hetero-Diels-Alder reaction takes place in comparable (or higher) yields and enantiomeric excesses.     

Asymmetric aldol reactions catalyzed by tryptophan in water

Tryptophan was shown to be able to catalyze direct aldol reactions between various cyclic ketones and aromatic aldehydes in water with high enantioselectivity.