Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Using Chiral Oxazoline-Based Ligands

Russian Journal of Organic Chemistry - Chiral oxazoline ligands containing an aromatic ring were prepared from norephedrine and pyrrole-2-carbonitrile or 2-hydroxybenzoyl chloride. The synthesized...     

平面手性二茂铁N,O-配体催化苯乙炔对醛的不对称加成反应

 以手性N,N-二甲基二茂铁乙胺为原料,采用文献报道的方法合成了两个具有平面手性的二茂铁N,O-配体,并将其应用到苯乙炔对醛的不对称加成反应之中,考察了不同溶剂和不同底物的影响. 结果表明,配体(R)-1-[(α-二甲胺基)乙基]-(S)-2-(二苯基羟基甲基)二茂铁催化剂对该类反应具有较高的催化活性及较好的手性诱导能力,乙醚是该体系最好的溶剂,苯甲醛为底物时可获得高达82%的对映选择性.     

双功能手性联萘酚配体在炔基锌对醛的不对称加成反应选择性能研究

单体2-溴吡啶, 2-溴-5-甲基吡啶, 2-氯-4-氟吡啶, 2-氯-3-三氟甲基吡啶分别与( R )-3,3′-二硼酸-2,2′-二甲氧基-1,1′-联萘 [( R )-2]在钯催化下, 通过Suzuki交叉耦合反应合成得到四个类似手性化合物( R )-3a-d。将它们应用到炔基锌对醛的不对称催化加成反应中,结果表明( R )-3a和( R )-3b的催化效果不好, 而( R )-3d只对脂肪醛有很好的催化效果,( R )-3c则对这类不对称催化反应均有很好的催化效果, 能给出高达95%的收率和99%的选择性结果。结果还表明所产生相应炔丙醇异构体构型为S,这与手性催化剂构型相反。     

Enantioselective Addition of Phenylacetylene to Aldehydes Catalyzed by Polymer-Supported Sulfonamide

Enantioselective formation of C-C bonds is an area of intense research. Among them, the asymmetric addition of alkynyl reagents to aldehydes is very useful for the synthesis of chiral secondary propargyl alcohols.[1] Recently, many significant homogeneous chiral ligands have been disclosed,[2,3] but very few efficient heterogeneous catalysts have been reported. Herein, we report our research results in the asymmetric addition of phenylacetylene to aldehydes catalyzed by polymer-supported chiral sulfonamide.     

The Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by 2-Methylquinoline Derived Chiral Ligands

One of the most important and fundamental synthetic procedures for the establishment of a carbon-carbon bond stereoselectively is the enantioselective addition of organometallic reagents to aldehydes affording chiral secondary alcohols1. In this process, a frequently used method is to perform the reaction in the presence of a chiral ligand such as amino alcohol2. Here, we first report that two new chiral ligands3, which were readily available by the reaction of chiral ketone with lithiated 2-m…     

Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Catalysed by Chiral Ligands Derived from L-Hydroxyproline

The Lithium salts of chiral auxiliaries 2–4 derived from L-Hydroxyprolin (2S, 4R)-1 catalysed the enantioselective addition of diethylzinc to aromatic aldehydes to afford sec alcohols in up to 80% optical purity.     

Enantioselective Addition of Chiral Organotitanium Derivatives to Aldehydes

Alkoxy- and aryloxy-organotitanium compounds 2–4 derived from (S)-2-methyl-1-butanol, (R)-2-butanol, (-)-menthol, quinine, cinchonine, and (S)-1.1′-binaphthol are added to aromatic aldehydes to give optically active alcohols 5–10 in enantioselectivities of up to 88% e. e., with nucleophilic transfer of methyl, phenyl, and 1-naphthyl groups. The Tables 1–3 list the effects of varying the reagents, the substrates, and the reaction conditions of the new asymmetric synthesis.     

Highly Enantioselective Phenylacetylene Addition to Benzaldehyde Catalyzed by Chiral Tridentate Ligand

Development of new or improved methods for the asymmetric preparation of chiral propargylic alcohols has gained considerable significance during the past years because they are useful building blocks for the synthesis of many biologically active compounds and natural products.[1] A series of chiral tridentate ligands were conveniently synthesized from amino acids with good yields (Scheme 1).[2] A preliminary study of the enantioselective alkynylation of benzaldehyde catalyzed by this chiral tridentate ligand was carried out and up to 83% ee of chiral propargyl alcohols was obtained (Table 1 ). A further investigation of the tridentate ligand is currently underway.     

手性氨基醇催化的苯乙炔与酮的对映选择性加成

(S)-(1-Benzylpyrrolidin-2-yl)diphenylmethanol and cinchonine were evaluated as promotors in the asymmetricadditions of phenylacetylene to ketones,in order to prepare chiral propargylic alcohols.Good yields(up to 89%)and moderate enantioselectivities(up to 77.9% ee)were achieved.Addition of Ti(OPr-i)_4 can significantly improvethe enantioselectivity of the reaction.     

Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Catalyzed by New Chiral Oxazolidine Ligand

Abstract

The chiral oxazolidine ligand can catalyze the enantioselective addition of diethylzinc to aromatic aldehydes at room temperature with high enantioselectivity (98–99% ee). The conditions for this catalytic process are both mild and simple as compared with the same kind catalyst.     

手性氨基酸酰胺催化二乙基锌与芳香醛不对称加成反应

将由磺酰化氨基酸和长链的含甲氧基官能团的胺制备的(S)-N-(4-甲氧基苯乙基)-3-苯基-2-(对甲基苯磺酰胺)丙酰胺(1d)手性配体用于催化二乙基锌与系列芳香醛对映选择性加成反应.15 mol%该催化剂能够对含有吸电子基团、供电子基团及不同位阻的芳香醛均有较好的效果,能够在比较温和的条件下获得高达87%ee和中等程度的产率.     

新型树状结构手性联二萘酚衍生物的合成及催化性能研究

报道了树状结构的手性联二萘酚(BINOL)配体的合成及其在二乙基锌对醛的不对称加成反应中的应用.(R)-2,2′-二羟基-1,1′-联萘-3,3′-二羧酸与末端为氨基的Frechet聚芳醚型树状分子经缩合反应,以中等产率得到0～3代的树状分子配体,用¹HNMR,IR和MALDI-TOF质谱进行了结构表征.这些树状手性配体与Ti(OPrⁱ)₄在无水甲苯溶液中形成的配合物是二乙基锌对醛不对称加成反应的高效催化剂,树状分子载体的体积对催化剂的对映选择性没有明显的影响.以邻氯苯甲醛为底物时,反应的对映选择性随树状分子代数的增加而有所提高.     

Highly Catalytic Enantioselective Addition of Diethyl Zinc to Aldehydes and Chalcone in the Presence of Chiral Ligands

Catalytic asymmetric carbon-carbon bond formation is one of the most important reactions and have attracted much attention to develop more efficient enantioselective C-C formation methods in organic synthesis. In this field, asymmetric addition of diethylzinc to aldehydes[1] and conjugate addition to enones[2] have drawn special interests and have been greatly developed. Regardless of it, much spaces in these areas still exist, so it needs more extensive and intensive researches for the purpose of as follows: (1) attaching ligands to a polymer for the easy separation of the catalysts so as to be able to allow very efficient recovery and reuse of the catalysts, and the possibility of carrying out the desired transfomation in continuous mode in a flow reactor, etc., (2) searching for novel chiral catalysts with such features as more suitable for more extensive substrates varieties, and more convenient and economical as well as possessing applicable prospect, and so on. Here we report some works in these areas done in our laboratory.     

Synthesis of Chiral Pyridylphenols for the Enantioselective Addition of Diethylzinc to Aldehydes

Chiral 8‐substituted 2‐(8,10,10‐trimethyl‐6‐aza‐tricyclo[7.1.1.0^2,7]undeca‐2(7),3,5‐trien‐5‐yl)‐phenols were prepared from a high enantiopurity (>97% ee) of (1R)‐(+)‐α‐pinene, and assessed in the enantioselective addition of diethylzinc to substituted benzaldehydes, giving the (S)‐alcohols with enantiomeric excess ranging from 33% to 89%. Interestingly, in all cases, except for those of ortho‐chlorobenzaldehyde, ortho‐ and para‐methoxybenzaldehydes, the ee was >71%. The plot of the Hammett substitution constants vs. enantiomeric excess of the diethylzinc addition to either the ortho‐ or para‐substituted benzaldehydes shows a linear correlation.     

Synthesis of Chiral Catalysts for the Enantioselective Addition of Diethylzinc to Aromatic Aldehydes

The reaction of diethylzinc with aromatic aldehydes and (S)-porretine derived catalysts was investigated. The synthesis of new chiral catalysts is also described.     

Enantioselective Diethylzinc Addition to Aromatic Aldehydes Catalyzed by Novel Ti(IV) Complex of Three-Dentate Chiral Sulfonamide Ligands

The synthesis of several novel three-dentate sulfonamide alcohol ligands is described, starting from camphorsulfonyl chloride. The influence of temperature and ligand structure on the asymmetric addition of dietylzinc to aromatic aldehydes has been studied. Enantioselectivities up to 76% have been obtained.     

Enantioselective Addition of Diethylzinc to Benzaldehyde by Catalysts of Chiral Heterocyclic Ligands

TheenantioselectiveadditionofdiethylzincreagentstoprochiralcarbonylgrouphasbeenachievedprincipallybycatalyticalamountofchiralP-aminoalcoholswhichhaveproventobehighlyeffectivecatalysts'.Ahydroxylgrouphasbeenregardedtobenecessaryforthechiralligandtoformazincalkoxideasthecatalyticspecies'.Wewishtoreporthereinontheethylationofbenzaldehydewithdiethylzincpromotedbyseveralkindsofoxazolidineandthiazolidinederivativeswhichdonotcontainhydroxylgroup.Fourkindschiralheterocyclicligandsweusedarelistedasfoll…     

Synergistic Peptide and Gold Catalysis: Enantioselective Addition of Branched Aldehydes to Allenamides

The combination of a peptide catalyst and a gold catalyst is presented for enantioselective addition reactions between branched aldehydes and allenamides. The two catalysts act in concert to provide γ,δ-enamide aldehydes bearing a fully substituted, benzylic stereogenic center – a structural motif common in many natural products and therapeutically active compounds – with good yields and enantioselectivities. The reaction tolerates a variety of alkyl and alkoxy substituted aldehydes and the products can be elaborated into several chiral building blocks bearing either 1,4- or 1,5- functional group relationships. Mechanistic studies showed that the conformational features of the peptide are important for both the catalytic efficiency and stereochemistry, while a balance of acid/base additives is key for ensuring formation of the desired product over undesired side reactions.     

Synthesis of Novel 1,4‐Bissulfonamide Ligands for Enantioselective Addition of Diethylzinc to Aldehydes

Several novel chiral sulfonamide ligands based on (1R,2S,4R,5S)‐1,4‐diamino‐2,5‐dimethylcyclohexane skeleton have been synthesized and their application in the enantioselective addition of diethylzinc to aldehydes was investigated in the presence of Ti(OⁱPr)₄. The effect of ligands, temperature and the loading amount of ligands was studied. Under optimized conditions, enantioselective addition of diethylzinc with various aryl aldehydes and aliphatic aldehydes proceeded smoothly and afforded chiral secondary alcohols in up to 88% ee.