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Kenichiro Itami

Publications and source records attributed to Kenichiro Itami.

At least 19 recordsLinked to original sources
PubMed2006

Direct C-H arylation of (hetero)arenes with aryl iodides via rhodium catalysis.

A new method for the catalytic C-H arylation of heteroarenes and arenes that manifests high activity paired with reasonably broad scope was developed. Under the catalytic influence of RhCl(CO){P[OCH(CF3)2]3}2 and Ag2CO3, the direct C-H arylation of heteroarenes/arenes with aryl/heteroaryl iodides took place to afford a range of biaryls in good to excellent yields with high regioselectivity. Thiophenes, furans, pyrroles, indoles, and alkoxybenzenes are applicable in this arylation protocol.

Benzene Derivatives↗
PubMed2006

Platform synthesis: A useful strategy for rapid and systematic generation of molecular diversity.

Emergence of library-based approaches have changed the way of developing new functional molecules in materials science and pharmaceutical science. Therefore, reliable methods for rapid and systematic generation of functional molecules are highly called for in this field. We herein describe our concept of "platform synthesis" as a useful strategy for generating molecular diversity. This simple yet powerful strategy realizes the synthesis of a number of interesting multifunctional molecules, such as multisubstituted olefins, in a programmable and diversity-oriented format. As well as applications to the synthesis of pharmaceutically important molecules, such as tamoxifen and CDP840, applications to materials science, which have led to the discovery of interesting fluorescent materials and properties, are also described.

Journal Article↗
PubMed2006

Sequential Pd- and Rh-catalyzed three-component cyclization with allenylboronate platform.

[reaction: see text] A novel three-component cyclization using allenylboronate ester is described. A three-component assembly of allenylboronate ester, aryl iodides, and stabilized carbon nucleophiles took place in the presence of palladium catalyst, furnishing functionalized alkenylboronate esters with high regio- and stereoselectivity. A Rh-catalyzed cyclization of the resultant three-component products then afforded interesting carbocyclic frameworks efficiently.

Journal Article↗
PubMed2006

Catalytic four-component assembly based on allenylboronate platform: new access to privileged allylic amine structures.

We developed a novel palladium-catalyzed four-component assembly based on allenylboronate platform, by which privileged allylic amine structures can be constructed in a regioselective, stereoselective, and diversity-oriented manner. The boryl group acts not only as a useful group that can be transformed to various functional groups afterward but also as a stereochemical controller in the generation of key (pi-allyl)palladium intermediates. A short synthesis of rolipram (selective phosphodiesterase-4 inhibitor) is also demonstrated.

Journal Article↗
PubMed2005

Rapid synthesis of CDP840 with 2-pyrimidyl vinyl sulfide as a platform.

A rapid synthesis of CDP840 (a potential therapeutic agent for asthma), using 2-pyrimidyl vinyl sulfide as a platform, has been established. This method includes a stereoselective double Mizoroki-Heck-type arylation, a Liebeskind-Srogl-type cross-coupling reaction, and a Pd/C-catalyzed hydrogenation.

Journal Article↗
PubMed2005

Triarylethene-based extended pi-systems: programmable synthesis and photophysical properties.

[reaction: see text] On the basis of an efficient Pd-catalyzed triarylation to a vinylsilane platform, four types of structurally well-defined triarylethene-based extended pi-systems have been prepared very rapidly. From a compound library constructed by the present method, it was possible to find a number of interesting fluorescent materials, as well as interesting fluorescent properties such as aggregation-induced enhanced emission. A useful method for the rapid synthesis and property evaluation has also been developed.

Journal Article↗
PubMed2005

Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents.

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.

Journal Article↗
PubMed2004

Pyrimidine-core extended pi-systems: general synthesis and interesting fluorescent properties.

We have developed a simple but powerful synthetic strategy that permits the assembly of pi-systems onto a pyrimidine core in a programmable and diversity-oriented format. The nucleophilic addition of ArLi to 2-methylthiopyrimidine, followed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidation, resulted in the production of 4-aryl-2-methylthiopyrimidines. The iterative reaction sequence then gave 4,6-diaryl-2-methylthiopyrimidines. The resulting adduct was further allowed to react with ArMgBr under the catalytic influence of NiCl2(dppe) to afford 2,4,6-triarylpyrimidines. By following this synthetic scheme, interesting pyrimidine-core pi-systems were rapidly constructed in a programmable fashion. The successful discovery of a number of interesting fluorescent materials and properties (e.g., solvatofluorochromism) speaks well for the potential of our platform strategy in the development of functional organic materials.

Journal Article↗
PubMed2004

Rapid construction of multisubstituted olefin structures using vinylboronate ester platform leading to highly fluorescent materials.

[reaction: see text] A catalytic one-pot triarylation on the C=C core of vinylboronate pinacol ester (1) produces extended pi-systems based on a multisubstituted olefin structure very rapidly. We established an efficient protocol for the Pd-catalyzed double C-H arylation of 1 with aryl halides, which was successfully integrated with C-B arylation with aryl halides (cross-coupling) in one pot. By using this method, several highly fluorescent materials with a wide range of color variations (blue to red) were discovered.

Journal Article↗
PubMed2004

Stereoselective synthesis of multisubstituted butadienes through directed Mizoroki-Heck reaction and homocoupling reaction of vinyl(2-pyridyl)silane.

[reaction: see text] We have developed the homocoupling reaction of alkenyl(2-pyridyl)silanes mediated by CuI and CsF, in which the strong directing effect of the 2-pyridyl group was observed. The homocoupling reaction was successfully integrated with the Mizoroki-Heck reaction of vinyl(2-pyridyl)silane with aryl halides, enabling a rapid and stereoselective synthesis of multisubstituted butadienes. From a relatively small compound library, it was possible to detect a number of fluorescent butadienes with a wide range of fluorescence color variations (blue to reddish-orange).

Journal Article↗
PubMed2004

Sequential assembly strategy for tetrasubstituted olefin synthesis using vinyl 2-pyrimidyl sulfide as a platform.

We have developed a programmable and diversity-oriented synthetic scheme for tetrasubstituted olefins through a site-selective and sequential assembly of pi-components onto a C=C core of vinyl 2-pyrimidyl sulfide. Noteworthy features are that (i) all components assembled stem from readily available organic halides or their Grignard reagents, (ii) the installation at the desired position can be achieved by the addition of the components in the appropriate order, and (iii) simple alteration of addition order in the sequence results in the production of all possible regio- and stereoisomers of multisubstituted olefins.

Journal Article↗
PubMed2004

Catalytic intermolecular Pauson-Khand-type reaction: strong directing effect of pyridylsilyl and pyrimidylsilyl groups and isolation of Ru complexes relevant to catalytic reaction.

Some circumstantial evidence for the directing effect of the 2-pyridylsilyl group in the Ru-catalyzed intermolecular Pauson-Khand-type reaction (PKR) of alkenyl(2-pyridyl)silane, alkyne, and carbon monoxide has been provided. Most importantly, we have succeeded in isolating several monometallic Ru complexes relevant to the catalytic reaction: Ru(vinylsilane)(CO)(3) complexes and ruthenacyclopentene. While the stoichimetric reaction of the Ru(vinylsilane)(CO)(3) complex with an alkyne led to the formation of the corresponding cyclopentenone (PKR product) at 100 degrees C, the ruthenacyclopentene intermediate was quantitatively produced at 50 degrees C. This complex was also converted to a cyclopentenone upon heating at 100 degrees C. Moreover, it was also found that the Ru(vinylsilane)(CO)(3) complex and ruthenacyclopentene serve as catalysts in intermolecular PKR.

Journal Article↗
PubMed2004

Cationic carbohydroxylation of alkenes and alkynes using the cation pool method.

The reactions of an N-acyliminium ion pool with alkenes and alkynes gave gamma-amino alcohols and beta-amino carbonyl compounds, respectively, after treatment with H(2)O/Et(3)N. The present reaction serves as an efficient method for cationic carbohydroxylation of alkenes and alkynes. When vinyltrimethylsilane was used as an alkene, the reaction was highly diastereoselective and served as an access to an enantiomerically pure alpha-silyl-gamma-amino alcohol. [reaction: see text]

Journal Article↗
PubMed2003

Diversity-oriented synthesis of tamoxifen-type tetrasubstituted olefins.

A general synthetic scheme for tamoxifen-type tetrasubstituted olefins based on the novel Cu-catalyzed carbomagnesation across alkynyl(2-pyridyl)silane has been developed. A wide array of electronically and structurally diverse tetrasubstituted olefins can be prepared in a regiocontrolled, stereocontrolled, and diversity-oriented manner. Noteworthy features are that (i) the three aryl groups, which are believed to be important (essential) for anti-estrogenic activity, can be varied at will because they all stem from readily available aryl iodides, and (ii) any stereo- and regioisomers can, in principle, be prepared by simply changing the applying order of aryl iodides into the sequence.

Alkenes↗