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Volume 70, Issue 4
Displaying 1-9 of 9 articles from this issue
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Preface
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Kazuhiko Takai2012 Volume 70 Issue 4 Pages 323
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL OPEN ACCESSDownload PDF (762K)
Reviews and Accounts
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Takashi Uemura2012 Volume 70 Issue 4 Pages 324-330
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESSRecently, Metal-Organic Frameworks (MOFs) or Porous Coordination Polymers (PCPs) composed of transition metal ions and bridging organic ligands have been extensively studied. The characteristic features of PCPs are highly regular channel structures, controllable channel sizes approximating molecular dimensions, designable surface potentials and functionality, and flexible frameworks responsive to guest molecules. Owing to these advantages, successful applications of PCPs range from molecular storage/separation to heterogeneous catalysts. In particular, use of their regulated and tunable nanochannels for a field of polymerization has allowed multi-level controls of polymerization (controls of stereoregularlity, molecular weight, etc.). Here I report on recent progress in polymerization utilizing the nanochannels of PCPs, and demonstrate why this polymerization system is attractive and promising, from the viewpoints of precision controls of polymer structures.View full abstractDownload PDF (3924K) -
Masafumi Ueda, Takeaki Naito, Okiko Miyata2012 Volume 70 Issue 4 Pages 331-342
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESSThe synthetic utilities of conjugated oxime ethers as a radical acceptor are described. The triethylborane-mediated intermolecular carbon radical addition to chiral conjugated oxime ether proceeded regio- and stereoselectively. The radical reaction of conjugated oxime ether with triethylborane in the presence of aldehyde afforded γ-butyrolactone via sequential process involving ethyl radical addition, generation of N-boryl enamine, aldol-type reaction with aldehyde and lactonization. On the other hand, treatment of conjugated oxime ether with triethylborane and thiophenol in the presence of O2 gave β-hydroxysulfides with high regioselectivity and good yield. The reaction would proceed through radical pathway involving regioselective addition and the subsequent trapping of the resulting α-imino radical with O2, where the imino group enhances the stability of the intermediate radical. The hydroxyalkylation reaction via carbon radical addition and hydroxylation with O2 was also developed.View full abstractDownload PDF (1856K) -
Kei Ohkubo, Shunichi Fukuzumi2012 Volume 70 Issue 4 Pages 343-353
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESSPhotocatalytic selective oxygenation reactions of aromatic compounds were achieved using an electron donor-acceptor linked dyad, 9-mesityl-10-methylacridinium ion (Acr+-Mes) as a photocatalyst and molecular oxygen as an oxidant under visible light irradiation in homogeneous conditions. The oxygenation reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of acridinium moiety of Acr+-Mes to afford an extremely long-lived electron-transfer state. The electron-transfer state can oxidize and reduce substrates and dioxygen, respectively, leading to selective oxygenation and halogenation of substrates. Photoinduced electron transfer from benzene to the singlet excited state of 3-cyanoquinolinium ion has enabled to oxidize benzene by dioxygen to yield phenol selectively. C-C bond formation of substrates has also been made possible by using Acr+-Mes as a photocatalyst.View full abstractDownload PDF (3072K) -
Takeshi Kawase2012 Volume 70 Issue 4 Pages 354-365
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESSRecently, polycyclic conjugated systems bearing carbocyclic five-membered rings have attracted much attention because of their utility in organic electronic devices. Despite possessing a 4nπ electron periphery, dibenzopentalenes are fairly stable compounds with a planar structure. Thus, appropriate modification would provide them with desirable electronic properties. Recently we found novel reactions yielding dibenzopentalene derivatives from readily available o-bromoethynylbenzenes using commercially available nickel complexes, and from 2-bromotolans via a novel amino migration reaction. These methods are accessible to π-extended pentalene derivatives bearing various functional groups and aromatic ring systems. Among them, a dinaphthylpentalene derivative showed very high hole mobility (1.8×10−3 cm2V−1s−1) as amorphous materials. Furthermore, it was employed as a p-type material for organic heterojunction photovoltaic cells (PCE=0.94%, Voc=0.96 V). It is the first pentalene derivative for organic thin-film semiconductors.View full abstractDownload PDF (2419K) -
Hiroyuki Kusama2012 Volume 70 Issue 4 Pages 366-381
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESSThe transition metal-catalyzed electrophilic activation of alkynes towards the attack of nucleophiles has been a subject of extensive study due to their high utility as useful methods for the construction of polycyclic compounds.
We have found that transition metal-containing carbonyl or azomethine ylides, novel bifunctional metal-containing reactive species, can be generated by treatment of ω-alkynyl carbonyl or imine derivatives with a catalytic amount of electrophilic transition metal complexes such as W(0) and Pt(II) complexes. These species turned out to behave both as an ylide and as a carbene complex during the reaction. Various types of heterocyclic and carbocyclic skeletons could be obtained in a single operation by using these species. Herein, we report the full account of our research based on the above methodology.View full abstractDownload PDF (4605K) -
Akihiro Ishiwata, Yukishige Ito2012 Volume 70 Issue 4 Pages 382-394
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL RESTRICTED ACCESS1,2-cis Glycosidic linkages are prevalent in natural glycans. Although key factors that control stereoselectivity of glycosylation have been largely understood, stereoselective synthesis of 1,2-cis glycosides is potentially problematic. To achieve exclusive formation of desired isomer, approaches based on intramolecular aglycon delivery (IAD) are of special promise. In the last two decades, various mixed acetal linkages and a number of glycosyl donor moieties have been making much progress to develop novel IAD strategies, mainly based on formation of the acetal linkages.
The methodology toward the strereoselective 1,2-cis glycosylation using naphthylmethyl (NAP) ether-mediated IAD has been developed. Namely, 2-O-NAP protected donor was cleanly converted to the mixed acetal upon oxidative activation with DDQ. Subsequent activation of thioglycosidic linkage initiated the rearrangement of an aglycon from mixed acetal moiety to give a desired 1,2-cis glycoside. Stereospecific constructions of various 1,2-cis linkages, which are not only β-mannopyranoside but also other linkages such as β-L-rhamno-, α-glucopyrano- and β-arabinofurano-sides, were achieved through NAP-IAD. This methodology was successfully applied to the synthesis of various fragments of natural glycans.View full abstractDownload PDF (2015K)
Review de Debut
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Hiroshi Takikawa2012 Volume 70 Issue 4 Pages 395-396
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL OPEN ACCESSCarbon-fluorine bonds are among the strongest single bonds, and their catalytic, selective activation is still a challenging issue in organic chemistry. Recently, a C-F bond activation by silylium ions has attracted considerable interest in this field, where strong silyl Lewis acids act as instrumental in assisting not only hydrodefluorination of benzyl and alkyl fluorides but also C-C bond formation via Friedel-Crafts reaction.View full abstractDownload PDF (948K)
Crossroad
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]2012 Volume 70 Issue 4 Pages 397
Published: April 01, 2012
Released on J-STAGE: April 24, 2012
JOURNAL OPEN ACCESSDownload PDF (727K)
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