Pinacol coupling reaction of beta-halo-alpha,beta-unsaturated aldehydes promoted by TiI4

The pinacol reaction of beta-halogenated alpha,beta-unsaturated aldehydes was promoted by titanium tetraiodide to give coupling products in good yields with high dl-selectivity. Subsequent reduction with H(2)/Pd-C gave saturated vic-diols in good yields. Heck coupling reaction enabled the displacement of halogens with vinyl groups without the loss of stereochemical integrities. [reaction: see text]     

(Chloromethyl)thallium(III) compounds

Aryl(chloromethyl)thallium chlorides, Ar(ClCH₂)TlCl (Ar=C₆H₅, p-CH₃C₆H₄) have been prepared by treatment of arylthallium dichlorides with diazomethane. The derived carboxylates, Ar(ClCH₂)TlX, react with HgX₂ to give the dicarboxylates, (ClCH₂)TlX₂ (X = OCOCH₃, OCOC₃H₇-i) and with tetramethyltin to give CH₃(ClCH₂)TlX compounds. R(ClCH₂)TIX compounds (R = CH₃, C₆H₅, p-CH₃C₆H₄) undergo disproportionation in methanol to R₂TlX and (ClCH₂)₂TlX compounds.     

Synthesis and γ-radiolysis of 2′-deoxy-5-fluorouridine and 5-fluorouridine derivatives

Seventeen compounds having a variety of substituents at the 3- and 5′-positions of 2′-deoxy-5-fluorouridine (5-FUdR) and 5-fluorouridine (5-FUR) were synthesized, and their γ-radiolysis in aqueous solutions were studied. The compounds having thioureido (RNHCSNH, R ? H, PhCH₂, acyl) and thiocarbonylamino (XCSNH, X ? PhCH₂S, PhO) groups at the 3-position of 5-FUdR were efficiently cleaved to give 5-FUdR with high G values upon γ-irradiation of their aqueous solutions. The active species for these cleavage reactions were hydrated electron (e^? _aq), H^? and HO^?. However, the compounds having a dimethylsulfoxyimino group at 3-position of 5-FUdR and 5-FUR afforded 5-FUdR and 5-FUR only under the radiolysis conditions where e^? _aq becomes a principal active species. The compound having a 2-benzoylthiazoylthiocarbonylamino group at the 3-position of 5-FUdR showed the highest reactivity toward HO^.. The mechanisms of these γ-radiolysis reactions are discussed. The examination of anticellular activities of γ-irradiated compounds having a thiocarbonylamino group at the 3-position of 5-FUdR toward murine Sarcoma 180 cells revealed that these compounds may be utilized as a candidate for a radiation-induced drug (RID).     

Chiral β-dimethylaminoalkylphosphines. Highly efficient ligands for a nickel complex catalyzed asymmetric grignard cross-coupling reaction

Chiral β-dimethylaminoalkylphosphines were prepared starting with amino acids, (S)-alanine, (S)-phenylalanine, (R)-phenylglycine, (S)-valine, and (R)-tert-leucine. The chiral phosphines were found to be highly efficient ligands for a nickel catalyzed asymmetric Grignard cross-coupling reaction (38～94% optical yield).     

Progress toward the total synthesis of ciguatoxins: a convergent synthesis of the FGHIJKLM ring fragment

[structure: see text] A highly convergent synthetic route to the FGHIJKLM ring fragment of ciguatoxins has been developed, which relied on extensive use of the B-alkyl Suzuki-Miyaura coupling reaction.     

A new method for the evaluation of the relative stability of organosulfur radicals by competitive elimination technique

The relative stability of various organosulfur radicals is estimated by competitive elimination technique using tributyltin radical and acetophenone derivatives having two different sulfur substituents at α and α positions.     

Photochemically generated silicon-carbon double-bonded intermediates VIII. Photolysis of phenyldisilane derivatives in the presence of olefins

Photolysis of phenylpentamethyldisilane, 1,1-diphenyltetramethyldisilane and 1-isopropyl-1-phenyltetramethyldisilane in the presence of a wide variety of olefins has been studied. All reactions investigated, with the exception of those with 1-methylcyclohexene and tetramethylethylene, afforded the corresponding 1/1 addition products. Yields of the adducts depended highly on the structure of the olefins used. In the photolysis of phenylpentamethyldisilane in the presence of an equimolar mixture of 1,1- and 1,2-bis(trimethylsilyl)ethene under competitive reaction conditions, the main product was the one arising from the 1,1-isomer. A possible mechanism for the process of addition of olefin to the photochemically generated silicon-carbon double-bonded intermediate (A) is discussed.     

Phase Relations in the Ni–Mn–Ga Ternary System and Aging Effect on Shape Memory Properties of Ferromagnetic Ni<Subscript>2</Subscript>MnGa Sputtered Films

Summary. Isothermal sections of the Ni–Mn–Ga ternary phase diagram at 1073 and 1273 K were investigated over a wide range of alloy compositions. The range of the β-Ni₂MnGa phase, its equilibria with the γ-(Mn, Ni), α′-Ni₃Ga, and γ-Ni₃Ga₂ phases, and the liquidus and solidus lines were determined experimentally. The aging effect on the shape memory effect (SME) of Ni₂MnGa sputtered films was also investigated. The two-way SME of the constraint-aged films was confirmed by the temperature change.     

Total synthesis of gambierol

[structure: see text] The first total synthesis of gambierol, a marine polycyclic ether toxin, has been achieved. The synthesis features the Pd(PPh3)4/CuCl/LiCl-promoted Stille coupling for the stereoselective construction of the sensitive triene side chain that includes a conjugated (Z,Z)-diene moiety.     

Silicon hydrides and nickel complexes : III. Hydrosilylation of olefins with dichloro[1,2-bis-(dimethylphosphino)-1,2-dicarba-closo-dodecaborane]-nickel(II) as catalyst

The hydrosilylation of olefins catalyzed by nickel(II) chloride complexed with 1,2-bis(dimethylphosphino)-1,2-dicarba-closo-dodecaborane produces terminal and internal adducts in comparable amounts. This unusual feature of the reaction is explained in terms of the electron-accepting nature of the carboranyl group.