手性苯并咪唑铜(Ⅱ)络合物催化合成1,1''''-联-2萘酚

In the past several decades, much attention has been paid to optically active, C2-asymmetric 1,1′-binaphthalene-2,2′-diol and its derivatives because of their application in inducing chirality in asymmetric synthesis[1,2]. Enantiomerically pure 1,1′-binaphthalene-2,2′-diol has been prepared by many methods ranging from the classical resolution via crystallization of the diastereoisomeric salts[3] to asymmetric oxidative coupling[4～6].     

Chiral Phosphino‐ and (Phosphinooxy)‐Substituted N‐Heterocyclic Carbene Ligands and Their Application in Iridium‐Catalyzed Asymmetric Hydrogenation

Enantiomerically pure iridium complexes with phosphino‐ and (phosphinooxy)‐substituted N‐heterocyclic carbene (NHC) ligands were synthesized. Investigation of their electronic properties showed a similar trans influence of the phosphino (or phosphinooxy) and the NHC units. The complexes were tested in iridium‐catalyzed hydrogenation. While low conversions were observed with unfunctionalized olefins, the catalysts proved to be suitable for hydrogenation of the α,β‐unsaturated ester 20 , allylic alcohol 21 , and imine 22 . The enantioselectivities were, however, moderate.     

Application of the chiral base desymmetrisation of imides to the synthesis of the alkaloid jamtine and the antidepressant paroxetine

The synthesis of the alkaloid jamtine and the antidepressant paroxetine have been addressed by a strategy involving asymmetric desymmetrisation of prochiral imides by a chiral lithium amide base. A short reaction sequence, starting with a cyclohexane fused succinimide, led to the structures originally reported for the alkaloid jamtine and its derived N-oxide. The structures synthesised are shown not to correspond with those originally reported. A second sequence involves desymmetrisation of a 4-arylglutarimide, and provides a short enantioselective synthesis of the drug substance paroxetine.     

Recycling Chiral Organocatalyst （4S）-Phenoxy-（S）-proline for Direct Asymmetric Aldol Reaction in Ionic Liquid （bmim）PF6

Room temperature ionic liquid (bmim)PF6 was evaluated for recycling an organocatalyst (4S)-phenoxy-(S)-proline for direct asymmetric aldol reactions. The desired aldol products were obtained with good yields up to 93.2% and enantioselectivities up to 88.5%, and isolation of the products by simple extraction allowed recycling the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Use of allyl, 2-tetrahydrofuryl, and 2-tetrahydropyranyl ethers as useful C3-, C4-, and C5-carbon sources: palladium-catalyzed allylation of aldehydes

Palladium-diethylzinc or palladium-triethylborane catalytically promotes self-allylation of 2-(allyloxy)tetrahydrofurans, 2-(allyloxy)tetrahydropyrans, and their hydroxy derivatives on the rings (ribose, glucose, mannose, deoxyribose, deoxyglucose). All the reactions proceed at room temperature and provide polyhydroxyl products, sharing a structural motif of a homoallyl alcohol, in good to excellent yields with high levels of stereoselectivity. Useful C3-unit elongation, which makes the best use of an allyl ether as a protecting group and a nucleophilic allylation agent, is demonstrated. Mechanisms for the umpolung reaction (of an allyl ether into an allylic anion) and stereoselectivity associated with allylation of aldehydes are discussed.     

Excess heat capacities and orientational order in systems containing hexadecane isomers of different molecular structure

Using the Picker flow microcalorimeter, excess heat capacities have been obtained at 25°C throughout the concentration range for 2,2-dimethylbutane,n-hexane, and cyclohexane each mixed with a series of hexadecane isomers of increasing degrees of orientational order, as determined by depolarized Rayleigh scattering. The isomers are 2,2,4,4,6,8,8-heptamethylnonane, 6-, 4-, and 2-methylpentadecane, andn-hexadecane. Thec _p ^E values are negative, increasing rapidly in magnitude with increase of orientational order, and are not predicted by the Prigogine—Flory theory which neglects order. Values ofc _p ^E are obtained at 10, 25, and 55°C for cyclohexane +6-, 4-, and 2-methylpentadecane which with other literature data lead to the temperature dependence of the thermodynamic excess functions for cyclohexane solutions of the five C₁₆ isomers. The excess enthalpy and entropy vary with the C₁₆ isomer and with temperature, but the corresponding variation of the excess free energy is small, indicating a high degree of enthalpy-entropy compensation. This is consistent with a rapid decrease with temperature of orientational order in the C₁₆ isomers.     

Stereodivergent total asymmetric synthesis of polyhydroxylated pyrrolidines via tandem allylic epoxidation and intramolecular cyclization reactions

Epoxidation of the allylic alcohols 10 and 11 using the VO(acac)₂/t-BuOOH system followed by an intramolecular 5-exo cyclization of the resulting δ-epoxycarbamates 12, 13, 18, and 19 has been shown to provide a general and efficient solution for the asymmetric synthesis of polyhydroxy pyrrolidines. The requisite vicinal amino alcohol functionality was enantio-/regio-selectively installed by the Os-catalyzed asymmetric aminohydroxylation reaction of the designed achiral olefin 6.     

New sulfur-coordinating chiral ligands for the Tsuji—Trost reaction

The use of sulfur-coordinating chiral ligands in the palladium-catalyzed asymmetric Tsuji—Trost reaction is reviewed.     

Synthesis and polymerization of N-[N′-(α-methylbenzyl)aminocarbonyl-n-alkyl]maleimide

Two types of optically active N-[N′-(α-methylbenzyl)amino/carbonyl-n-alkyl]maleimides (MBAC) were synthesized from maleic anhydride, 6-amino-n-caproic acid (or 12-amino-n-dodecanoic acid), and (R)-(+)-α-methylbenzylamine. Radical homopolymerizations of MBAC were performed in several solvents at 60 and 110°C for 24 h to give optically active polymers. Radical copolymerizations of MBAC were performed with styrene (ST) and methyl methacrylate (MMA) in dioxane at 60°C. The monomer reactivity ratios and the Alfrey-Price Q-e values were determined. Chiroptical properties of the polymers and copolymers were investigated. © 1995 John Wiley & Sons, Inc.