Selectively substituted thiophenes and indoles by a tandem palladium-catalyzed multicomponent reaction

A variety of di- and trisubstituted thiophenes were synthesized by a one-pot palladium-catalyzed ortho-alkylation sequence terminated by either Heck or C-H coupling. Initial results toward the functionalization of indoles are also presented.     

Palladium complex catalyzed reaction of diphenylketene with terminal acetylenes giving disubstituted acetylenes

The reaction of diphenylketene with terminal acetylenes catalyzed by tetrakis-(triphenylphosphine)palladium gave disubstituted acetylenes in high yields.     

Anionic WS-TEMPO-mediatory electrooxidation of alcohols in water: halide-free oxidation directed towards a totally closed system

Electrooxidation of alcohols in water with water-soluble N-oxyl derivatives bearing a sulfonic acid group (anionic WS-TEMPOs) as a mediator proceeded to afford the corresponding ketones and aldehydes in moderate to good yields. The aqueous solution containing WS-TEMPOs could be readily recovered and reused for the electrooxidation of alcohols, thereby providing a totally closed system.     

Synthesis, structures and electrochemical properties of ruthenium (II) complexes bearing bidentate 1,8-naphthyridine and terpyridine analogous (N,N,C)-tridentate ligands

1,8-Naphthyridine (napy) and terpyridine-analogous (N,N,C) tridentate ligands coordinated ruthenium (II) complexes, [RuL(napy-κ²N,N′) (dmso)](PF₆)₂ (1: L=L¹=N″-methyl-4′-methylthio-2,2′:6′,4″-terpyridinium, 2: L = L² = N″-methyl-4′-methylthio-2,2′:6′,3″-terpyridinium) were prepared and their chemical and electrochemical properties were characterized. The structure of complex 1 was determined by X-ray crystallographic study, showing that it has a distorted octahedral coordination style. The cyclic voltammogram of 1 in DMF exhibited two reversible ligand-localized redox couples. On the other hand, the CV of 2 shows two irreversible cathodic peaks, due to the Ru-C bond of 2 containing the carbenic character. The IR spectra of 1 in CO₂-saturated CH₃CN showed the formation of Ru-(η¹-CO₂) and Ru-CO complexes under the controlled potential electrolysis of the solution at −1.44 V (vs. Fc/Fc⁺). The electrochemical reduction of CO₂ catalyzed by 1 at −1.54 V (vs. Fc/Fc⁺) in DMF-0.1 M Me₄NBF₄ produced CO with a small amount of HCO₂H.     

Ruthenium-catalyzed s-propargylation of thiols enables the rapid synthesis of propargylic sulfides

A new and highly efficient catalytic system based on CpRuClL2 is proposed for the S-propargylation of thiols by propargylic carbonates under neutral conditions, in which specific requirements inherent to the different reactivities of aliphatic and aromatic thiols are achieved by tuning both the nature of the ancillary ligand L and the experimental conditions.     

Ru(η-1,3,5-cyclooctatriene)(η-dimethyl fumarate)2: a novel, versatile zerovalent ruthenium complex with electron-deficient olefinic ligands

The reactivity of a novel zerovalent ruthenium complex, Ru(η⁶-cot)(η²-dmfm)₂ (cot = 1,3,5-cyclooctatriene, dmfm, =dimethyl fumarate), which is readily prepared from Ru(η⁴-cod)(η⁶-cot) (cod = 1,5-cyclooctadiene) and dmfm was examined. The reaction with monodentate phosphine or amine ligands gave Ru(η⁶-cot)(dmfm)(L) (L = ligand) via dissociation of dmfm. Among bidentate phosphines, dppm (dppm = bis(diphenylphosphino)methane) reacted to give Ru(η⁴-cot)(dmfm)(dppm) along with releasing a dmfm ligand. In the case of dppe (dppe = 1,2-bis(diphenylphosphino)ethane), two types of complexes were obtained depending on the reaction conditions, Ru(dmfm)(dppe)₂ and an alkyl alkenyl complex; in the formation of the latter complex, sp² C-H bond activation of dmfm occurred. Ru(η⁴-cot)(dmfm)(N^?N) and Ru(dmfm)₂ (N^?N^?N) were formed by reacting with bidentate and tridentate nitrogen ligands. The reactions with arenes gave π-coordinated complexes, Ru(η⁶-arene)(dmfm)₂. p-Quinones and a p-biqunone reacted to give Ru(η⁶-cot)(p-quinone) and {Ru(η⁶-cot)}₂(p-biquinone), respectively, along with the dissociation of two dmfm ligands. It was found that low-valent ruthenium complexes preferably bear both electron-donating and accepting ligands simultaneously to be thermodynamically stable.     

X-ray molecular structure of the 1:1 adduct of [FeH(CO)4]− and dimethyl acetylenedicarboxylate. η3-[trans-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate

The crystal structure of a bis(triphenylphosphine)iminium salt of the 1:1 adduct of [FeH(CO)₄]^? and dimethyl acetylenecarboxylate has been determined from three-dimensional X-ray data collected by the counter method. Single crystals belong to the triclinic space space group P$\text{1}$, with two units of [C₃₆H₃₀NP₂]⁺[C₁₀H₇FeO₈]^? in a cell of dimensions: $\text{a}$ = 13.918(2), $\text{b}$ = 15.669(5), $\text{c}$ = 9.909(2) Å, $\text{α}$ = 91.22(3), $\text{β}$ = 94.83(2), and $\text{γ}$ = 77.62(2)°. The structure was refined to a conventional $\text{R}$ of 0.068 for 5373 observed

reflections. The resulting structure indicates that the complex anion is η³-[$\text{trans}$-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate, the coordination around the iron atom being described as a considerably distorted trigonal bipyramid. A comparison of the present structure with the structures of related complexes suggests that the η³-acryloyl portion is best represented as an intermediate of (η³-allyl) with the oxygen atom and (η²-olefin + η¹-acyl). The short Fe-C(acyl) length of 1.897(5) Å implies an enhanced back-donation of electrons from the iron atom to the acyl group.     

Photochemically generated silicon—carbon double-bonded intermediates : XII. Some properties of silacyclopropenes and silapropadienes produced by photolysis of ethynylpolysilanes

The photolysis of six ethynyl-substituted polysilanes has been investigated in the presence or absence of methanol. Irradiation of 1-ethynyl-2-phenyl- and 1-ethynyl-1-phenyltetramethyldisilane (I and II), 1-ethynyl-1,1-diphenyltrimethyldisilane (III) and 2-ethynylheptamethyltrisilane (V) in the presence of methanol produced methoxysilanes arising from the corresponding reactive silacyclopropene and silapropadiene intermediates. Irradiation of 1-enthynylheptamethyltrisilane (IV) led to the formation of dimethylsilylene, ethynylpentamethyldisilane and 1,1-dimethyl-2-pentamethyldisilanyl-1-silacyclopropene intermediate. The photolysis of tris(trimethylsilyl)ethynylsilane (VI) in the presence of methanol produced 1-trimethylsilyl-1-bis(trimethylsilyl)methoxysilylethene and hexamethyldisilane. Photolysis of II and III in the absence of a trapping agent gave the respective bis(silyl)acetylenes, via a 1,2-hydrogen shift, from the transient silacyclopropenes, in moderate yields, whereas the yields of the rearranged acetylenes from IV and V were low.