不对称Reformatsky反应

综述了６０年代至今不对称诱导和不对称催化Ｒｅｆｏｒｍａｔｓｋｙ拔应的研究，进展参考文献１９篇。     

Enantioselective synthesis induced by chiral organic-inorganic hybrid silsesquioxane in conjunction with asymmetric autocatalysis

5-Pyrimidyl alkanol with up to 96% ee was formed using chiral organic-inorganic hybrid silsesquioxane in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde, in conjunction with asymmetric autocatalysis.     

Nonlinear Effects in Asymmetric Synthesis and Stereoselective Reactions: Ten Years of Investigation

Who would have thought before 1986 that an enantiomerically impure catalyst could give a product in an asymmetric synthesis with an enantiomeric excess higher than that of the catalyst? Until then it was assumed that the ee value of the product (ee_prod) from an asymmetric synthesis was linearly correlated to the ee value of the chiral auxiliary (ee_aux)—in fact a large deviation is possible (see diagram). These nonlinear effects are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.     

新型手性膦-硼烷配合物的合成及其在不对称催化氢化反应中的应用

以苯乙烯为原料,通过Sharpless不对称二羟基化反应合成高对映体纯的苯基乙二醇,经酯化、亲核取代反应转化为手性膦-硼烷配合物.后者克服了有机膦配体易氧化的缺点,其制备过程简单,易于提纯,在空气中可长期保存.该手性膦-硼烷配合物在四氟硼酸-甲醚的存在下解络,生成的自由膦不经分离直接与[Rh(COD)Cl]₂作用生成手性膦-铑原位催化剂.在α-乙酰氨基肉桂酸甲酯的不对称氢化反应中,转化率为100%,对映选择性88%e.e.     

5-羟基色胺受体激动剂(1R,2S)-(-)-2-(2-羟基苯基)-N,N-二丙基环丙胺的不对称合成

利用手性双唑啉与三氟甲磺酸亚铜催化2-甲氧基苯乙烯与重氮乙酸二环己基甲酯的不对称环丙烷化反应合成了手性环丙烷羧酸酯,用氢氧化钠对其进行选择性水解得到全反式环丙烷羧酸,其ee值经GC测定为88%.进一步经过Curtius重排、烷基化等反应及重结晶等步骤合成了光学纯的具有生理活性的环丙胺化合物1a和1b.     

手性高分子金属络合物在不对称催化中的应用

综述了手性高分子金属络合物（人工合成）在不对称催化中的应用及最新进展,参考文献５３篇。     

On the scope of diastereoselective epoxidation of various chiral auxiliaries derived enones: the conformational analysis of camphor derived N- and O-enones

Various camphor derived N- and O-enones were treated with selected oxidants to provide the corresponding epoxides in a wide range of diastereoselectivity. For camphorsultam derived activated alkenes, high to excellent stereoselectivities were obtained when the s-trans enones were treated with methyl(trifluoromethyl)dioxirane. On the other hand, for exo-10,10-diphenyl-2,10-camphanediol (3) and exo-10,10-diphenyl-10-methoxy-2-camphanol (4) derived alkenes, the use of s-cis enones gave the desired epoxide with excellent diastereoselectivity under the same reaction conditions. The stereoselectivity was highly dependent on the geometry of the auxiliaries derived enones and the stereochemical induction is discussed.     

Axially Chiral Aryl‐Alkene‐Indole Framework: A Nascent Member of the Atropisomeric Family and Its Catalytic Asymmetric Construction

A new class of axially chiral aryl‐alkene‐indole frameworks have been designed, and the first catalytic asymmetric construction of such scaffolds has been established by the strategy of organocatalytic (Z/E)‐selective and enantioselective (4+3) cyclization of 3‐alkynyl‐2‐indolylmethanols with 2‐naphthols or phenols (all >95 : 5 E/Z, up to 98% yield, 97% ee). This reaction also represents the first catalytic asymmetric construction of axially chiral alkene‐heteroaryl scaffolds, which will add a new member to the atropisomeric family. This approach has not only confronted the great challenges in constructing axially chiral alkene‐heteroaryl scaffolds but also provided a powerful strategy for the enantioselective construction of axially chiral aryl‐alkene‐indole frameworks.     

Enantioselective syntheses of (E)-γ,δ-disubstituted homoallylic alcohols via BF3·OEt2-catalyzed aldehyde allylboration and analysis of the origin of E-selectivity: A1,2 allylic strain vs. syn-pentane interaction

Enantioselective allylboration of aldehydes with α-substituted β-methyl allylboronate was reported. By using BF₃·OEt₂ as the catalyst, γ,δ-disubstituted homoallylic alcohols were obtained in good yields with high E-selectivities and enantioselectivities. Transition state analysis revealed that the disfavored transition state suffers from a syn-pentane interaction between the BF₃ catalyst and axially oriented α-substituent of the allylboron reagent. Such a syn-pentane interaction is severe enough to overcome the A^1,2 allylic strain between the β-methyl group and the α-substituent of the boron reagent that is present in the favored competing transition state. Consequently, the reaction proceeded with equatorial placement of the α-substituent to furnish γ-methyl substituted homoallylic alcohols with high E-selectivity.     

Asymmetric hydroboration and Matteson homologation for the preparation of fluorinated α-phenethanols

The asymmetric catalytic hydroboration-oxidation of ring-fluorinated styrenes (F-PhCHCH₂) was achieved with catecholborane along with a combination of [Rh(COD)₂]⁺BF₄⁻ and (R)-BINAP providing 81-96% enantioselectivities for the product alcohols for ortho-unhindered styrenes. A deleterious effect of a 2,6-disubstitution on the enantioselectivity of the product alcohol was observed. 2-Trifluoromethylstyrene also provides only 53% ee, probably due to the steric bulk of the CF₃ group at the ortho-position of styrene. Asymmetric homologation of fluorophenylmetals (magnesium bromide or lithium) with pinanediol α-chloroethylboronate, followed by oxidation readily furnished the desired 1-(2,6-difluorophenyl)- and 1-(perfluorophenyl)ethanols in 94-95% ee.     

Kinetic Influences on Enantioselectivity for Non-Diastereopure Catalyst Mixtures

Different kinetic rate laws were observed for two diastereomeric catalysts which separately gave opposite enantioselectivities in the asymmetric hydrogenation of the dimethyl ester of itaconic acid. In reactions carried out using an equal mixture of the two catalysts, a conversion-dependent enantioselectivity was predicted from the separate reaction-rate data, in agreement with the experimentally observed final enantioselectivity of 54.8 % ee (see diagram).     

Enantioselective synthesis of cyclic allylboronates by Mo-catalyzed asymmetric ring-closing metathesis (ARCM). A one-pot protocol for net catalytic enantioselective cross metathesis

Mo-catalyzed asymmetric ring-closing metathesis (ARCM) reactions are used to synthesize cyclic allylboronates of high optical purity (89% ee to >98% ee). A one-pot procedure involving formation of allylboronates, Mo-catalyzed ARCM and functionalization of the optically enriched cyclic allylboronates constitutes net asymmetric cross metathesis (ACM). Structural modification of ARCM products include reactions with aldehydes to afford optically enriched compounds that bear quaternary carbon centers with excellent diastereoselectivity. These studies emphasize the significance of the availability of chiral Mo-based complex as a class of chiral metathesis catalysts that frequently complement one another in terms of reactivity and selectivity.     

新型手性磷化合物的合成及其作为配体催化剂在某些不对称合成反应中的应用

从L-氨基酸、D-樟脑、(-)-假麻黄碱、(-)-α-苯乙胺、(S)-(-)-联萘二酚等旋光源出发,合成了26个三配位及四配位手性磷化合物.作为配体催化剂,试验了它们在潜手性酮及亚胺的不对称硼烷还原反应、醛与二乙基锌的不对称烷基化反应以及醛的不对称硅腈化反应中的催化活性.发现其中有些催化剂有很好的立体选择性.     

Efficient stereodivergent synthesis of 1,4-dideoxy-1,4-iminohexitols from an (S)-glyceraldimine

A stereodivergent synthesis of 1,4-dideoxy-1,4-imino-d-mannitol I and d-allitol III from an (S)-glyceraldimine, which is easily prepared from d-mannitol, has been achieved with overall yields of 62% and 49%, respectively. The synthesis is based on the addition of vinylmagnesium bromide to N-benzylimine 1, derived from readily available (R)-2,3-O-isopropylideneglyceraldehyde, followed by N-allylation or N-acryloylation, ring-closing metathesis and asymmetric dihydroxylation.     

Towards Perfect Asymmetric Catalysis: Additives and Cocatalysts

Make your catalyst more enantioselective! The enantiomeric excess of a catalytic reaction system can sometimes be enhanced from below 10 to over 90 % by the use of suitable achiral additives. Since completely different mechanisms can influence the catalyst and reaction outcome, there is a range of additives that can be applied to improve the catalyst efficiency for a variety of organic reactions.     

Catalytic enantioselective allylation at the activated benzylic position of prochiral aryl cyano esters: access to quaternary stereogenic centers

Palladium catalyzed asymmetric allylic alkylation of prochiral aryl cyano esters has been carried out in the presence of various chiral ligands. The base and additives have been varied and allowed to produce the allyl derivative presenting a highly functionalized quaternary stereogenic center. The chiral pocket ligands of Trost appears the most appropriate to produce the desired chiral derivative.     

Combining chiral elements: a novel approach to asymmetric phase-transfer catalyst design

A new dicationic asymmetric phase-transfer catalyst, designed by combining chiral elements, is described. Catalytic testing using standard glycine imino ester alkylations shows good yields and moderate enantioselectivities.     

Asymmetric addition of chiral triquinphosphoranes on activated carbonyl compounds

Chiral triquinphosphoranes react with trifluoroacetophenone, ketopantolactone and aromatic aldehydes affording pairs of hydroxyphosphoranes diastereomers with a diastereoselectivity up to 90% depending on the nature of the electrophile. In the case of ketopantolactone, hydroxyphosphorane diastereomers are quantitatively converted to alkoxyphosphoranes with a decreasing of diastereomeric excesses. The major alkoxyphosphorane diastereomer exhibits a close SP structure determined by x-ray diffraction analysis.     

Metal-free asymmetric hydrogenation and hydrosilylation catalyzed by frustrated Lewis pairs

The activation of H₂ for the catalytic hydrogenation of unsaturated compounds is one of the most useful reactions in both academia and chemical industry, which has long been predominated by the transition-metal catalysis. However, metal-free hydrogen activation represents a formidable challenge, and has been less developed. The recent emerging chemistry of frustrated Lewis pairs (FLPs) with a combination of sterically encumbered Lewis acids and Lewis bases provides a promising approach for metal-free hydrogenation due to their amazing abilities for the challenging H₂ activation. In the past several years, the hydrogenation of a wide range of unsaturated compounds using FLP catalysts has been successfully developed. Despite these advances, the corresponding asymmetric hydrogenation is just in its start-up step. Similar to the mode of HH bond activation, SiH bond can also be activated by FLPs for the hydrosilylation of ketones and imines. But its asymmetric version is also not well-solved. This Letter will outline the recent important progress of metal-free catalytic asymmetric hydrogenation and hydrosilylation using FLP catalysts.     

Synthesis of a new fluorinated oxazolidinone and its reactivity as a chiral auxiliary in Aldol reactions

A new enantiomerically pure fluorinated oxazolidinone has been prepared from a fluorinated imidoyl chloride and an optically pure sulfoxide. The diastereoselective reduction of the β-iminosulfoxide thus formed followed by elimination of the sulfoxide and cyclization of the created aminoalcohol furnishes the desired product. The fluorinated oxazolidinone was subsequently used as a chiral auxiliary in Aldol reactions. We also found that the selective formation of the syn-Evans and syn-non-Evans diastereoisomer can be controlled by adjusting the Lewis acid/base ratio.