摘要:
An process for epoxidizing diversely functionalized olefins by oxorhenium catalysis employs conditions which control water concentration. By controlling water concentration, one can maximize monoperoxo complex formation and increase turnover which subsequently reduces diol side products obtained from epoxide ring opening and increases the yield of the desired epoxide product. The optimal range of water concentrations is 0.50-80.0 mol %. Using less than 0.5 mol % water does not result in practical turnovers and 1.0 equivalent of water (or more) is detrimental to the lifetime of the active catalytic species formed. More particularly, there are four aspects to controlling water concentration: 1) anhydrous oxidants using trialkylsilyl peroxides and an in situ source of BTSP eliminating the need for its isolation; 2) water removal agents including molecular sieves (Aldrich, 3 Å, 4 Å) and common inorganic dehydrating agents; 3) rhenium catalysts; and 4) a boiling reactor process in the context of oxorhenium catalyzed epoxidation.
摘要:
This invention provides a method for preparing a 1,2,3-triazole compound comprising contacting an organic azide with a 2-substituted-1-haloalkyne, in the presence of a copper catalyst and a copper-coordinating ligand (preferably a tertiary amine) in a liquid reaction medium, thereby forming a 1,4,5-substituted-1,2,3-triazole compound including a halo substituent at the 5-position of the triazole, the organic portion of the organic azide at the 1-position of the triazole, and the substituent of the 1-iodoalkyne at the 4-position of the triazole. A method for preparing 1-iodoalkynes is also provided.
摘要:
A convenient process for the regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles and 1,4,5-trisubstituted 1,2,3-triazoles from organic azides and alkynes employs catalytic ruthenium.
摘要:
The high efficiency and fidelity of click chemistry permits a large number of diverse dendrimers encompassing a wide variety of functionalities at the chain ends, repeat units, and/or core to be prepared. Almost quantitative yields were obtained during the synthesis. In some cases, filtration or solvent extraction was the only method required for purification. These features represent a significant advancement in dendrimer chemistry and demonstrate an evolving synergy between organic chemistry and functional materials.
摘要:
Anthraquinone chiral ligands (AQN) are used in asymmetric aminohydroxylation addition reactions of cinnamate based olefins for synthesizing aryl serines. The anthraquinones impart a reverse regioselectivity as compared to the commonly employed phalazine chiral ligands (PHAL). Carbamates are employed as the oxidant nitrogen source. The yields and enantiomeric efficiencies are Excellent. .beta.-Hydroxyamines are obtained by deprotecting the corresponding .beta.-hydroxycarbamate.
摘要:
Osmium-catalyzed methods of addition to an olefin are discussed. In the method of asymmetric dihydroxylation of the present invention, an olefin, a chiral ligand, an organic solvent, an aqueous solution, a base, a ferricyanide salt and an osmium-containing compound are combined. The chiral ligand is an alkaloid or alkaloid derivative linked to an organic substituent of at least 300 daltons molecular weight through a planar aromatic spacer group. The organic substituent can be another alkaloid or alkaloid derivative. With the described chiral ligands, asymmetric dihydroxylation of olefins with high yields and enantiomeric excesses are achieved.
摘要:
Stable, optically active enantiomers of substituted glyceraldehydes or glycidaldehydes are synthesized by using osmium-catalyzed asymmetric dihydroxylation of an olefin which is a substituted 1,5-dihydro-3H-2,4-benzodioxepine. For example, the protected glyceraldehyde, 3-(1,2-dihydroxyethyl)-1,5-dihydro-3H-2,4-benzodioxepine and the protected glycidaldehyde, 3-(1,2-epoxyethyl)-1,5-dihydro-3H-2,4-benzodioxepine have been synthesized and the optical enantiomer has been recovered. In the synthetic and isolation methods, enantiomers with high enantiomeric excess are recovered from the mother liquor following a recrystallization step.
摘要:
A series of AB-type amphiphilic dendritic polyesters have been prepared divergently, in which two hybrids were coupled via the copper(1)-catalyzed triazole formation.
摘要:
Rhenium-catalyzed epoxidation of olefinic substrates is accelerated by the use of acclerants having a nitrogenous aromatic heterocyclic structure. Use of the accelerants also enables the use of aqueous hydrogen peroxide as an oxidant. To achieve optimum acceleration, the accelerant should have a concentration within a range from 2.0 mole percent to 100 mole percent of the acclerant with respect to 1 mole of the olefinic substrate. Use of the accelerant also results in an increased yield with respect to the conversion of the olefinic substrate to epoxide product.
摘要:
.beta.-Hydroxyamines and .beta.-hydroxycarbamates are synthesized from olefin substrates by means on a catalyzed asymmetric addition reaction. The addition reaction is catalyzed by osmium and is co-catalyzed by chiral ligands. The chiral ligands, in addition to being co-catalysts with the osmium, also serve to direct the addition reaction regioselectively and enantioselectively. Divalent ligands are preferred over monovalent ligands because of their enhance regio- and enantio-selectivity. Carbamates are employed as an oxidant nitrogen source for the production of .beta.-hydroxysulfonamides. Excellent yields and enantiomeric efficiencies are achieved with co-solvents containing a 50/50 (v/v) mixtures of water and organic solvent. The performance of the reaction is further enhanced by omitting the addition silver or mercurial salts conventionally employed in asymmetric aminohydroxylation additions to olefins performed in neat or substantially neat solvents. .beta.-Hydroxyamines are then obtained by deprotecting the corresponding .beta.-hydroxycarbamate.