Enantiomerically pure 2-bromo-2'-diphenylphosphinyl-1,1'- binaphthyl as a monophosphorus template for electrophilic functionalization in chiral MOP-type ligand synthesis

[reaction: see text] Pd-catalyzed monophosphinylation of (R)-2-bromo-2'-iodo-1,1'-binaphthyl with Ph(2)P(O)H afforded (R)-2-bromo-2'-diphenylphosphinyl-1,1'-binaphthyl in good yield with excellent chemoselectivity and no observable racemization. Subsequent lithiation in the presence of excess thiosulfonate furnished an enantiomerically pure sulfenylation product, which was reduced to afford a chiral S-MOP ligand.     

n-type organic field-effect transistors with very high electron mobility based on thiazole oligomers with trifluoromethylphenyl groups

Novel thiazole oligomers and thiazole/thiophene co-oligomers with trifluoromethylphenyl groups were developed as n-type semiconductors for OFETs. They showed excellent n-type performances with high electron mobilities. A 5,5'-bithiazole with trifluoromethylphenyl groups forms a closely packed two-dimensional columnar structure leading to a high performance n-type FET. The electron mobility was enhanced to 1.83 cm2/Vs on the OTS-treated substrate.     

One-pot sequential four-component coupling via Cp*RuCl-catalyzed cyclotrimerization and Suzuki-Miyaura coupling

The catalytic intermolecular cyclotrimerization of alkynylboronates, propargyl alcohols, and terminal alkynes was accomplished by means of the ruthenium catalysis and the temporary tethering approach with the C-B-O linkage to give rise to highly substituted arylboronates with excellent selectivity. The resultant arylboronates were further converted to highly substituted biaryls via the Suzuki-Miyaura coupling with various aryl iodides using Pd₂(dba)₃/PCy₃ as a catalyst precursor in aqueous toluene. As a consequence, the four-component coupling approach to highly substituted biaryls was successfully established by combining these two operations into a sequential one-pot process.     

Asymmetric conjugate reduction of alpha,beta-unsaturated ketones and esters with chiral rhodium(2,6-bisoxazolinylphenyl) catalysts

New asymmetric conjugate reduction of beta,beta-disubstituted alpha,beta-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2-one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60 degrees C in 95 % ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO)2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-beta-methylcinnamate and beta-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98 % ee.     

First Principle Calculation of the Geometrical and Electronic Structure of Impurity-Doped β-FeSi2 Semiconductors

The geometrical and electronic structures of impurity (Cr, Mn, Co, Ni)-doped β-FeSi₂ were investigated using first principles pseudopotential calculations based on generalized gradient approximation (GGA) density function theory. The calculated structural parameters depend strongly on the kinds of dopants and sites. The total energy calculations for substitution of dopants at the Fe_I and the Fe_II sites revealed that Mn prefers the Fe_I site, whereas Cr, Co, and Ni prefer the Fe_II site. The electronic structure is analyzed and discussed in terms of the atomic charges, bond overlap population, and total and partial densities of states (DOS).     

One-pot carbon-carbon bond formation at the β-position of cyclic ketones: oxidative Michael addition with alkyl malonates

A carbon-carbon bond was formed at the β-position of cyclic ketones in a one-pot manner by oxidation with N-tert-butylbenzenesulfinimidoyl chloride, followed by the reaction of malonic acid esters or potassium cyanide.     

Radiation-Induced Cross-Linking of Polyethylene in the Presence of Various Acetylenic Compounds

A study was made on the radiation-induced cross-linking reaction of polyethylene by exposing film samples to [ddot]Co γ-rays in vacuum or in the presence of various acetylenic compounds such as acetylene, its C₃ to C₅ higher derivatives, and their mixture with tetrafluoroethylene (TFE). The samples (0.2 mm thick) were found to decrease in weight when irradiated in vacuum, but to increase in the presence of the additives. The IR spectrum measurements of the resultant showed that the trans-vinylene unsaturation increased by the irradiation, especially in the presence of the C₃ to C₅ derivatives, and terminal vinyl increased markedly in acetylene. However, the formation of these unsaturations were depressed when the film was irradiated in the mixed gas with TFE. The rate of the cross-linking reaction was accelerated by the addition of acetylene-TFE, acetylene, trifluoromethyl-acetylene, perfluorobutyne-2, perfluorobutyne-2-TFE, and methylacetylene-TFE [G(cross-linking) = 4.4-1.2]. It was reduced with methylacetylene, butyne-1, butyne-1-TFE, pentyne-1, pentyne-1-TFE, pentyne-2, pentyne-2-TFE, [G(cross-linking) = 0.6-0.1]. On the basis of these experimental results a chain reaction scheme of the cross-linking is proposed, and it is discussed on the basis of the activation energy of the elementary reactions.     

Efficient Generation and Synthetic Applications of Alkyl-Substituted Siloxycarbenes: Suppression of Norrish-Type Fragmentations of Alkanoylsilanes by Triplet Energy Transfer

Acylsilanes have been known to undergo isomerization to siloxycarbenes under photoirradiation and the thus generated carbenes can be utilized for various synthetic reactions. But this carbene formation is not necessarily efficient with some alkanoylsilanes because Norrish-type fragmentations compete, which limit the synthetic utility of alkanoylsilanes as carbene precursors. In this study, generation of siloxycarbenes from alkanoylsilanes by visible-light-induced energy transfer was examined by using an Ir complex, [Ir{dF(CF₃)ppy}₂(dtbpy)]PF₆, and was successfully applied to the C−C coupling reactions with boronic esters or aldehydes. This methodology efficiently suppressed undesired Norrish-type reactions and broadened synthetic utility of alkanoylsilanes.     

Flow microreactor synthesis of tricyclic sulfonamides via N-tosylaziridinyllithiums

Tricyclic sulfonamides were synthesized by the generation of aziridinyllithiums from N-tosylaziridines followed by an intramolecular nucleophilic reaction and the subsequent reaction with electrophiles using a flow microreactor system. The reactions could be carried out at 0 °C, although much lower temperatures such as ?78 °C are needed for batch macro reactors.     

Generic guiding principle of HTSC material design for high-field application

Through the analyses on the irreversibility lines (ILLs) under H||c for various high-T_c superconducting (HTSC) single-crystalline samples, we found two universal functions representing ILLs. In these functions, the electromagnetic anisotropy factor γ² plays a crucial role. The appropriate chemical substitution, such as Bi(Pb)2212, is an effective method to improve flux pinning properties via decreasing γ².