Catalytic carbonylation reactions of benzyne derivatives.
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Biomedical subjects
N Chatani
Publications and source records attributed to N Chatani.
Ru(3)(CO)(12)-catalyzed coupling reaction of sp(3) C-H bonds adjacent to a nitrogen atom in alkylamines with alkenes.
Catalytic reactions which involve the cleavage of an sp(3) C-H bond adjacent to a nitrogen atom in N-2-pyridynyl alkylamines are described. The use of Ru(3)(CO)(12) as the catalyst results in the addition of the sp(3) C-H bond across the alkene bond to give the coupling products. A variety of alkenes, including terminal, internal, and cyclic alkenes, can be used for the coupling reaction. The presence of directing groups, such as pyridine, pyrimidine, and an oxazoline ring, on the nitrogen of the amine is critical for a successful reaction. This result indicates the importance of the coordination of the nitrogen atom to the ruthenium catalyst. In addition, the nature of the substituents on the pyridine ring has a significant effect on the efficiency of the reaction. Thus, the substitution of an electron-withdrawing group on the pyridine ring as well as a substitution adjacent to the sp(2) nitrogen in the pyridine ring dramatically retards the reaction. Cyclic amines are more reactive than acyclic ones. The choice of solvent is also very important. Of the solvents examined, 2-propanol is the solvent of choice.
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Iridium(I)-catalyzed cycloisomerization of enynes.
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The ruthenium-catalyzed reductive decarboxylation of esters: catalytic reactions involving the cleavage of acyl-oxygen bonds of esters.
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Ynolate chemistry. Reaction of a silylynolate with aziridines leading to gamma-lactams.
A silylynolate, generated via the carbonylation of lithium silyldiazomethane, was reacted with N-tosyl aziridines to produce various five-membered lactams in good yields. The key step of this reaction involves the ring-opening ketenylation of aziridines by the silylynolate. The reaction proceeded in a highly stereoselective manner, and ketenylation took place at the less hindered carbon. When treated with aldehydes prior to protonation, the alpha-silylated lactam enolates gave alpha-vinylidene gamma-lactams. These reactions represent a unique path to the generation of and for controlling the reactivity of a rare class of reactive intermediates, namely, acyllithium derivatives and ynolates.
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Reaction of o-oxazolinylphenyllithium with carbon monoxide. Carbonylative cyclization via an aroyllithium intermediate
The carbonylation of a phenyllithium containing an oxazoline group at the ortho position, followed by quenching with water, afforded a tricyclic compound, 3,3-dimethyl-2,3-dihydrooxazolo[2, 3-a]isoindol-5(9bH)-one, in 91% yield. This reaction proceeded via an intramolecular cyclization of the aroyllithium species, to give the tricyclic dienolate. Treatment of the tricyclic dienolate with electrophiles, such as alkyl halides, aldehydes, ketones, and epoxides gave the substituted oxazolo[2,3-a]isoindolinones in good yield.
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Ru(II)- and Pt(II)-catalyzed cycloisomerization of omega-aryl-1-alkynes. Generation Of carbocationic species from alkynes and transition metal halides and its interception by an aromatic ring
The treatment of aryl-1-alkynes, such as 4-aryl-1-butyne, 5-aryl-1-pentyne, and 6-aryl-1-hexyne, with catalytic amounts of transition metal chlorides, such as PtCl(2) and [RuCl(2)(CO)(3)](2), at 80 degrees C in toluene results in cycloisomerization to give dihydronaphthalenes or dihydrobenzocycloheptenes, in which the cyclization mode is dependent on the length of the tethers. The reaction is limited to substrates containing terminal alkynes. A key step of the reaction is the intramolecular interception by an aromatic ring of the vinylmetal complex 2, which contains a cation center at the beta-position, generated from the electrophilic addition of transition metal halides toward an alkyne. The more electron-rich aryl systems are more reactive.
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Acylation of five-membered N-heteroaromatic compounds by ruthenium carbonyl-catalyzed direct carbonylation at a C-H bond
The ruthenium-catalyzed carbonylation at the C-H bond of five-membered N-heteroaromatic compounds is described. The reaction of imidazoles with CO and olefins in toluene in the presence of a catalytic amount of Ru(3)(CO)(12) results in carbonylation of the C-H bond at the 4-position (adjacent to the sp(2)-nitrogen) of the imidazole ring to give acylated imidazoles in good to high yields. A wide range of olefins can be utilized in the carbonylation reaction, and a variety of functional groups are compatible under the reaction conditions. Other five-membered N-heteroaromatic compounds, such as pyrazoles, oxazoles, and thiazoles, can also be used for the carbonylation reaction, and in all cases, carbonylation takes place exclusively at a C-H bond alpha to the sp(2) nitrogen. The reactivity of the five-membered heterocycles corresponds to the pK(a) of the conjugate acid of these heterocycles. The higher the pK(a) of the substrate, the higher is the reactivity. This indicates that the pK(a) values are related to the ability of the nitrogen atom in the substrates to coordinate to a ruthenium center. The coordination of the substrates to the ruthenium center in the catalyst complex is a necessary prerequisite for the carbonylation to proceed.
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Direct carbonylation at a C-H bond in the benzene ring of 2-phenyloxazolines catalyzed by Ru(3)(CO)(12). Scope, limitations, and mechanistic aspects
The ruthenium-catalyzed carbonylation at a C-H bond in the benzene ring of a 2-phenyloxazoline is described. The reaction of 2-phenyloxazolines with CO and ethylene in toluene in the presence of a catalytic amount of Ru(3)(CO)(12) resulted in propionylation at an ortho C-H bond in the benzene ring. The presence of the oxazoline ring on the benzene ring is essential for the carbonylation to proceed. Other heterocycles, such as oxazine, oxazole, and thiazoline rings, also served as acceptable directing groups as did the oxazoline ring. A wide functional group compatibility was observed. The site selectivity of the carbonylation was examined using meta-substituted phenyloxazolines. It was found that the carbonylation took place exclusively at the less-hindered C-H bond, irrespective of the nature of substituents, indicating that the site selectivity was determined by steric factors. The reaction was also applicable, not only to a benzene ring, but also to naphthyl and thiophenyl rings. Olefins such as propene and trimethylvinylsilane in place of ethylene could also be used in the carbonylation reaction, while other olefins, such as 1-hexene, tert-butylethylene, vinylcyclohexane, isoprene, 1,5-hexadiene, cyclohexene, 1, 5-cyclooctadiene, styrene, methyl acrylate, vinyl acetate, allyltrimethylsilane, and triethoxyvinylsilane did not afford the coupling products. An equilibrium between 2-phenyloxazolines, carbon monoxide, and olefins exists on one hand and the corresponding ketones on the other hand, and product composition is governed by the equilibrium thermodynamics of the system. The results of deuterium labeling experiments suggest that the catalysis involves a reversible C-H bond cleavage and that the rate-determining step is not the cleavage of a C-H bond. The results of kinetic study of the effects of CO pressure show that the reaction rate accelerates with decreasing CO pressure.
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Effect of cytokinin 4PU30 on organ differentiation and dihydroisocoumarin production in amacha callus cultures.
Effect of a suitable combination of 1-naphthaleneacetic acid (NAA) and cytokinin N-(2-chloro-4-pyridyl)-N'-phenylurea (4PU30) concentrations, regarding organ differentiation and dihydroisocoumarin production, was examined in Hydrangea macrophylla var. thunbergii callus cultures. The callus cultured in a Linsmaier-Skoog medium containing 10(-5) M NAA and 10(-5) M 4PU30 under a light condition gave the highest level for callus growth, shoot formation, and phyllodulcin 8-O-glucoside content.
2,4-Dichlorophenoxyacetic Acid↗
[Quantitative analysis of dihydroisocoumarin constituents of Hydrangeae Dulcis Folium by means of high performance liquid chromatography. Chemical characterization of the processing, distribution in plant, and seasonal fluctuation].
In order to characterize the chemical change of the constituents during the processing of Hydrangeae Dulcis Folium, quantitative analyses of phyllodulcin, hydrangenol, and their 8-O-glucosides were developed by means of high performance liquid chromatography. As an application of this HPLC method, the distribution of those dihydroisocoumarins in different parts of Hydrangea macrophylla var. thunbergii was investigated. It was found that these dihydroisocoumarins were contained at the highest concentration in the leaves. Furthermore, the seasonal fluctuation of these compounds in the leaves, together with the height of the plant and total dry weight of the leaves, were clarified and so that the suitable period for the harvest of Hydrangea macrophylla var. thunbergii was deduced to be from Oct. to Nov.
Benzopyrans↗
[Crude drugs from aquatic plants. III. Quantitative analysis of triterpene constituents in alismatis rhizoma by means of high performance liquid chromatography on the chemical change of the constituents during alismatis rhizoma processing].
As a series of study on the evaluation of Alismatis Rhizoma and the chemical characterization of the processing, a quantitative method by high performance liquid chromatography (HPLC) for ten triterpene constituents, alisols A, A monoacetate, B, B monoacetate, E 23-acetate, F, and G and 13,17-epoxyalisol A, 11-deoxyalisols B and B 23-acetate, has been developed. By the use of this HPLC method, the contents of these triterpenes in various Alismatis Rhizoma and the fresh rhizoma of Alisma oriental JUZEPC, originated from in China, Taiwan, and Japan were examined. Furthermore, the chemical change of the triterpene constituents during the drying process of the rhizoma of Alisma oriental has been investigated and it was found that the bioactive triterpenes of Alismatis Rhizoma such as alisol A and alisol A monoacetate were artificially formed during the drying process.
Chromatography, High Pressure Liquid↗
[Qualitative and quantitative analysis of bioactive principles in Zingiberis Rhizoma by means of high performance liquid chromatography and gas liquid chromatography. On the evaluation of Zingiberis Rhizoma and chemical change of constituents during Zingiberis Rhizoma processing].
As a continuing study on the evaluation of various Zingiberis Rhizoma and the chemical characterization of the processing, a quantitative method by high performance liquid chromatography (HPLC) for 6, 8, 10-gingerol (1, 2, 3), 6,8-shogaol (4, 5), 6-dehydrogingerdione (6), and galanolactone (7) has been developed. By the use of this HPLC method, the contents of these compound in twenty kinds of Zingiberis Rhizoma [originating in China, Taiwan, Vietnam, and Japan (Shizuoka Prefecture)] and fresh ginger root cultivated in Shizuoka Prefecture were examined. It was found that Japanese Zingiberis Rhizoma and fresh ginger root contained 6-gingerol (1), 6-dehydrogingerdione (6), and galanolactone (7) as major constituents, whereas 7 was not detected in imported Zingiberis Rhizoma and 6 was detected in Vietnamese Zingiberis Rhizoma. Furthermore, the contents of 1 and 7 in fresh ginger root decreased remarkably during the processing procedure for Zingiberis Rhizoma. In addition, anti-ulcer sesquiterpene constituents in seven kinds of Zingiberis Rhizoma were analyzed by means of gas liquid chromatography (GLC).
Chromatography, Gas↗
Thunberginols A, B, and F, new antiallergic and antimicrobial principles from hydrangeae dulcis folium.
Six new antiallergic and antimicrobial principles, thunberginols A, B, C, D, E, and F, were isolated from Hydrangeae Dulcis Folium, the fermented and dried leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO. The chemical structures of thunberginols A, B, and F have been determined on the basis of chemical and physiocochemical evidence. Thunberginols A, B, and F showed more potent antiallergic activity than phyllodulcin, hydrangenol, and AA-861 in the in vitro test using the Schults-Dale reaction in sensitized guinea pig bronchial muscle. Thunberginols A, B, and F also exhibited antimicrobial activity against oral bacteria.
Animals↗
Thunberginols C, D, and E, new antiallergic and antimicrobial dihydroisocoumarins, and thunberginol G 3'-O-glucoside and (-)-hydrangenol 4'-O-glucoside, new dihydroisocoumarin glycosides, from Hydrangeae Dulcis Folium.
New antiallergic and antimicrobial dihydroisocoumarins, thunberginols C, D, and E, were isolated from Hydrangeae Dulcis Folium, the fermented and dried leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO, together with new dihydroisocoumarin glycosides, thunberginol G 3'-O-glucoside and (-)-hydrangenol 4'-O-glucoside. Their chemical structures have been determined on the basis of chemical and physicochemical evidence. Thunberginols C, D, E, G, and (-)-hydrangenol 4'-O-glucoside showed antiallergic activity in the in vitro bioassay using the Schults-Dale reaction in sensitized guinea pig bronchial muscle, and they also exhibited antimicrobial activity against oral bacteria.
Animals↗