Enantioselective Cyclopropanation Catalyzed by Gold(I)-Carbene Complexes

The formation of polysubstituted cyclopropane derivatives in the gold(I)-catalyzed reaction of olefins and propargylic esters is a potentially useful transformation to generate diversity, therefore any method in which its stereoselectivity could be controlled is of significant interest. We prepared and tested a series of chiral gold(I)-carbene complexes as a catalyst in this transformation. With a systematic optimization of the reaction conditions, we were able to achieve high enantioselectivity in the test reaction while the cis:trans selectivity of the transformation was independent of the catalyst. Using the optimized conditions, we reacted a series of various olefins and acetylene derivatives to find that, although the reactions proceeded smoothly and the products were usually isolated in good yield and with good to exclusive cis selectivity, the observed enantioselectivity varied greatly and was sometimes moderate at best. We were unable to establish any structure-property relationship, which suggests that for any given reagent combination, one has to identify individually the best catalyst.     

Highly Enantioselective Hetero-Diels-Alder Reaction of 1,3-Bis(silyloxy)-1,3-dienes with Aldehydes Catalyzed by Chiral Disulfonimide

Bulking up with F: The title reaction proceeds using 1?mol?% of the new perfluoroisopropyl chiral disulfonimide catalyst 1 to deliver several 2,6-disubstituted and 2,5,6-trisubstituted dihydropyrones in good yields and with excellent enantiomeric ratios. The utility of this methodology is illustrated with the first enantioselective synthesis of a potent aromatase inhibitor.     

Enantioselective Aldol Reaction with Difluoroenoxysilanes Catalyzed by Cationic Palladium Aqua Complexes

The enantioselective addition of difluoroenoxysilanes to aromatic aldehydes, catalyzed by cationic palladium aqua complexes, has been described. The reaction is operationally simple, does not require anhydrous conditions and performs at room temperature. The palladium catalysts, previously discovered and reported by Sodeoka, are easily prepared in two steps from PdCl₂(MeCN)₂. The aldol compounds were obtained in good yields and with enantiomeric ratios up to 93 : 7, the reaction being more efficient using electron-rich aldehydes.     

C2对称性有机小分子催化的高对映选择性Aldol反应

以环己酮与4-硝基苯甲醛直接不对称Aldol缩合为模型反应,对一系列具有C2对称性的有机小分子催化剂进行了考察,其中(2S,5S)-吡咯烷-2,5-二羧酸的不对称催化效果最好.在10℃下,以DMSO为溶剂,30%摩尔分数催化剂用量,研究了多个取代芳香醛和环己酮的不对称催化Aldol反应,对映选择性为87%～99?.     

C2对称性有机小分子催化的高对映选择性Aldol反应

以环己酮与4-硝基苯甲醛直接不对称Aldol缩合为模型反应, 对一系列具有C2对称性的有机小分子催化剂进行了考察, 其中(2S,5S)-吡咯烷-2,5-二羧酸的不对称催化效果最好. 在10 ℃下, 以DMSO为溶剂, 30%摩尔分数催化剂用量, 研究了多个取代芳香醛和环己酮的不对称催化Aldol反应, 对映选择性为87%～99% ee.     

金(I)配合物催化乙烯加氢的反应机理

采用密度泛函理论B3LYP方法, 对两类金(I)配合物AuX (X=F, Cl, Br, I)和AuPR₃⁺(R=F, Cl, Br, I, H, Me,Ph)催化C₂H₄加氢反应的机理进行了理论研究. 计算显示Au(I)配合物对C₂H₄氢化具有较好的催化效果, 其作用下的加氢反应存在“活化H―H键后再与C₂H₄反应”和“活化C＝C键后再与H₂反应”两种途径, 前者的活化能较后者低90-120 kJ·mol^-1, 因而具有明显的能量优势. 研究表明AuPR₃⁺ 的催化能力明显强于AuX. 此外, X/PR3基团供、吸电子能力的变化对配合物的催化能力也具有较为显著的影响. 电子结构分析显示Au(I)配合物在C₂H₄ 加氢反应中不仅能够削弱H―H、C＝C 键的强度, 还使H₂ σ_H―H^*、C₂H₄ π_C＝C^* 轨道能级下降, 从而缩小了π_C＝C-σ_H―H^*或σ_H―H-π_C＝C^*轨道间的能级差, 促进了C₂H₄-H₂反应中的电子离域, 从而降低禁阻反应发生的难度.σ_H―H^*、π_C＝C^*轨道能级改变量与加氢反应活化能E_a的降低值之间存在较好的一致性关系, 因此使上述轨道能级下降幅度越大的Au(I)配合物可以获得较好的催化效果.     

Synthesis and Anti-Proliferative Activity of Novel Tricyclic Compounds Derived from 2-Substituted 1,3-Indandione

A new series of fused 1,3-indandione derivatives has been synthesized and evaluated for anti-proliferative activity. 2-Alkene-1,3-indandione derivatives have been used as the precursors of a number of tricyclic compounds. The latter have been tested for anti-proliferative activity.     

Reaction of 2-Mono- and 2,2-Disubstituted 1,3-Dioxolanes with 1-Ethyl-3-hexylaluminacyclopentane

Reaction of 2-mono- and 2,2-disubstituted 1,3-dioxolanes with 1-ethyl-3-hexylaluminacyclopentane involves cleavage of the Al-C bond of the metal cycle and formation, after hydrolysis, ethylene glycol monoethers. Catalytic amounts of ZrCl4 or Ni(acac)₂ drive the reaction with 2-monosubstituted 1,3-dioxolanes.     

Enantioselective,Stereodivergent Hydroazidation and Hydroamination of Allenes Catalyzed by Acyclic Diaminocarbene (ADC) Gold(I) Complexes

The gold‐catalyzed enantioselective hydroazidation and hydroamination reactions of allenes are presented herein. ADC gold(I) catalysts derived from BINAM were critical for achieving high levels of enantioselectivity in both transformations. The sense of enantioinduction is reversed for the two different nucleophiles, allowing access to both enantiomers of the corresponding allylic amines using the same catalyst enantiomer.     

Enantioselective,Stereodivergent Hydroazidation and Hydroamination of Allenes Catalyzed by Acyclic Diaminocarbene (ADC) Gold(I) Complexes

The gold‐catalyzed enantioselective hydroazidation and hydroamination reactions of allenes are presented herein. ADC gold(I) catalysts derived from BINAM were critical for achieving high levels of enantioselectivity in both transformations. The sense of enantioinduction is reversed for the two different nucleophiles, allowing access to both enantiomers of the corresponding allylic amines using the same catalyst enantiomer.     

Enantioselective Alkynylation of 2‐Trifluoroacetyl Imidazoles Catalyzed by Bis‐Cyclometalated Rhodium(III) Complexes Containing Pinene‐Derived Ligands

Chiral rhodium(III) complexes containing two cyclometalating 2‐phenyl‐5,6‐(S,S)‐pinenopyridine ligands and two additional acetonitriles are introduced as excellent catalysts for the highly enantioselective alkynylation of 2‐trifluoroacetyl imidazoles. Whereas the ligand‐based chirality permits the straightforward synthesis of the complexes in a diastereomerically and enantiomerically pure fashion, the metal‐centered chirality is responsible for the asymmetric induction over the course of the catalysis. For comparison, the analogous iridium congeners provide only low enantioselectivity, and previously reported benzoxazole‐ and benzothiazole‐based catalysts do not show any catalytic activity for this reaction under standard reaction conditions.     

Quantum Chemical Study of the Preferred Conformations,Molecular Geometries,and Relative Thermodynamic Stabilities of 2-Substituted 4-Methylene-1,3-Dioxolanes and 4-Methyl-1,3-Dioxoles

The preferred conformations, molecular geometries, and relative stabilities of carbon–carbon double-bond exo–endo isomeric 2-substituted 4-methylene-1,3-dioxolanes (a) and 4-methyl-1,3-dioxoles (b) have been studied by DFT calculations at the B3LYP/6-31G* level of theory. The main interest of this work was devoted to the contribution of alkoxy substituents on the relative thermodynamic stabilities of these isomeric unsaturated acetals. Comparison of the computational data with previous experimental findings shows both the enthalpies and entropies of the a b isomerization to be accurately predictable by the DFT calculations. Most importantly, the good agreement between experiment and theory proved also to be applicable to the previously observed unexpectedly large effect of 2-alkoxy substitution on the isomer equilibria.     

Chemistry of Dioxacycloalkanes: VII. Synthesis and Properties of Substituted 1,3-Dioxolanes Derived from Carbocyclic Aldehydes

Reactions of 3-cyclohexenecarbaldehyde, 6-methyl-3-cyclohexenecarbaldehyde, bicyclo[2.2.1]-hept-5-ene-endo-2-carbaldehyde, benzaldehyde with 1,2-propanediol, 3-chloro-1,2-propanediol gavethe corresponding 2,4-substituted 1,3-dioxolanes. Their reactions with peroxyacetic acid, bromine, dichloro-carbene, and nucleophiles were studied. The effect of the substituents in the diol and aldehyde on their relative reactivity is discussed.     

Complexes of Cobalt(II) and Zinc(II) with Heterocyclic Compounds Derived from 1,3-Indanedione

Complexes of Co(II) and Zn(II) with three-membered structures containing 1,3-indanedione, 1,3,4-thiadiazole, and pyridine moieties were obtained.     

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…     

稀土化合物催化丁醛Aldol-Tishchenko反应的研究

1　实　验已有一些用稀土化合物催化Ｔｉｓｈｃｈｅｎｋｏ和Ａｌ ｄｏｘ Ｔｉｓｈｃｈｅｎｋｏ反应的报道[1～ 4 ] ,本文所用的催化剂对空气和水汽都很敏感 ,所有操作均须用Ｓｃｈｌｅｎｋ技术在氩气保护下进行。溶剂四氢呋喃(ＴＨＦ)和甲苯经无水ＣａＣｌ2 干燥 ,使用前经二苯甲酮 钠回流至蓝紫色蒸出。丁醛经 0 .4ｎｍ分子筛干燥后 ,在氩气保护下蒸出。稀土离子含量用ＥＤＴＡ络合滴定法测定。产物的收率在岛津公司生产的ＧＣ 14Ｂ型气相色谱仪上测定。1.1　催化剂的合成　　 (ＭｅＣｐ) 3 Ｌｎ由无水ＬｎＣｌ3与ＭｅＣｐＮａ按 1∶3摩尔…