Time‐Dependent Emission Enhancement of the Ethynylpyrene‐o‐Carborane Dyad and Its Application as a Luminescent Color Sensor for Evaluating Water Contents in Organic Solvents

The time‐dependent emission enhancement (TDEE) phenomena of the 1‐(o‐carboran‐1‐yl)ethynylpyrene dyad were reported. It was found that the emission intensity from the dyad increased in tetrahydrofuran (THF), acetone and dichloromethane with increasing incubation time. From the mechanistic studies, it was suggested that agglomeration of the dyad gradually proceeded in these media, followed by expression of excimer luminescence. Additionally, it was shown that the rates of TDEE of the dyad were sensitively accelerated in the presence of a trace amount of water. Based on this fact, a detection system for water contents in acetone was constructed. Before and after incubation for 96 h at room temperature, time courses of changes in optical properties were monitored. Finally, water contents in acetone can be estimated by the degrees of TDEE and emission color changes in the range from 0.1 wt % to 2.0 wt % and from 2.0 wt % to 20 wt %, respectively.     

A Convenient Route to α-Alkoxy Ester from Olefin Vla Organoborane-Catalyzed Hydroalumintaion

Organoborane-catatyzed hydroalumination of olefin with dichloroaluminum hydride and subsequent functionalization of the resulting organoaluminum with methyl α-chloro-α-methoxyacetate give rise to the corresponding α-methoxy ester in good yield.     

Palladium(Ti)-Catalyzed Claisen Rearrangement of 1-Phenylethenyl 2-Propenyl Ethers

Allyl vinyl ethers containing phenyl group at a position of vinyl ether readily undergo the Claisen rearrangement in the presence of a palladium(II) catalyst to give phenyl homoallyl ketones in good yields.     

A Two-Step Synthesis Of (±)-Blastmycinolactol Using Acylurea

A convenient synthesis of natural (±)-blastmycino-lactol from the aldol addition reaction of n-pentanoylurea and (±)-2-benzyloxypropionaldehyde is described.     

Cocrystallization of Two Different Pseudorotamers of Monocyclic Phosphorane Bearing Two Martin Ligands

Solution and crystal structures of monocyclic pentacoordinate phosphoranes bearing two Martin ligands and two carbon substituents are described. When the two carbon substituents are different, relative apicophilicity of the two monodentate carbon substituents could be determined based on the equilibrium ratio of the pseudorotamers. In some cases, x-ray structural analysis could be carried out and the crystallized structure from CH 3 CN is consistent with the major pseudorotamer in solution (CD 3 CN). Furthermore, when the equilibrium ratio of pseudorotamers is almost unity, novel cocrystallization of two pseudorotamers in a single crystal was observed.     

Role of B(C6F5)3 in activating the nickel-methyl complex (η-C5H5)Ni(CH3)(PPh3) to initiate the vinyl polymerization of norbornene

The Ni-methyl complex (η⁵-C₅H₅)Ni(CH₃)(PPh₃) (1) reacted with B(C₆F₅)₃ to give an unstable contact ion-pair complex with a μ-methyl bridge between the Ni and B atoms. Formation of the B-CH₃ bond was confirmed by the reaction of this complex with PPh₃ to give [(η⁵-C₅H₅)Ni(PPh₃)₂][B(CH₃)(C₆F₅)₃] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded (η⁵-C₅H₅)Ni(C₆F₅)(PPh₃) which is very stable and does not show any reactions with norbornene with or without added B(C₆F₅)₃. ¹⁹F NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C₆F₅)₃ system has the C₆F₅ end-group. A series of reactions, which includes CH₃/C₆F₅ exchange between the Ni and B centers with concomitant dissociation of PPh₃ to accept coordination of a norbornene monomer, is proposed as the route to active species that can initiate vinyl polymerization of norbornene.     

Iridium Catalysis for C?H Bond Arylation of Heteroarenes with Iodoarenes

Efficient couplings using equimolar quantities of each coupling partner and multiple C? H bond arylation reactions are achieved with an Ir‐based catalytic system for the C? H bond arylation of electron‐rich heteroarenes with iodoarenes to construct extended π‐systems. The dramatic ligand effect on reaction efficiency leads to the discovery that Crabtree's catalyst (see scheme) is the optimal catalyst precursor.

     

Photoreactive nanomatrix structure formed by graft‐copolymerization of 1,9‐nonandiol dimethacrylate onto natural rubber

Formation of photoreactive nanomatrix structure was investigated by graft‐copolymerization of an inclusion complex of 1,9‐nonandiol dimethacrylate (NDMA) with β‐cyclodextrin (β‐CD) onto natural rubber particle using potassium persulfate (KPS), tert‐butyl hydroperoxide/tetraethylenepentamine (TBHPO/TEPA), cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA), and benzoyl peroxide (BPO) as an initiator. The graft copolymer was characterized by ¹H NMR and FTIR after coagulation. The conversion of NDMA and the amount of residual methacryloyl group were found to be 58.5 w/w % and 1.81 w/w %, respectively, under the suitable condition of the graft‐copolymerization. The morphology of the film specimen, prepared from the graft copolymer, was observed by transmission electron microscopy (TEM) after staining the film with OsO₄. Natural rubber particle of about 1.0 μm in diameter was dispersed in poly(NDMA) matrix of about 10 nm in thickness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2418–2424, 2010     

Application of a chiral copper-1,1-bis{2-[(4S)-tert-butyloxazolinyl]}cyclopropane catalyst for asymmetric cyclopropanation of styrene

The structural effects of the bridge moiety and 5-position on bisoxazoline ligands were studied for the copper-catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate. The 1,1-bis{2-[(4S)-tert-butyloxazolinyl]}cyclopropane ligand showed a remarkable enhancement in the stereoselectivities (trans/cis = 84/16, >99.9% ee for the trans product) compared with the previously reported best ligand, 2,2-bis{2-[(4S)-tert-butyloxazolinyl]}propane (trans/cis = 75/25, 99.0% ee for the trans product).     

Kehokorins A-C, novel cytotoxic dibenzofurans isolated from the myxomycete Trichia favoginea var. persimilis

Kehokorins A (1)-C (3), three novel dibenzofurans, have been isolated from field-collected fruit bodies of the myxomycete, Trichia favoginea var. persimilis, and their structures were elucidated by spectral data. Kehokorin A (1) was a α-l-rhamnopyranoside of kehokorin B (2), while kehokorin C (3) was a 1-demethoxy analog of 2. Kehokorin A (1) was cytotoxic against HeLa cells with an IC₅₀ value of 1.5 μg/mL.