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The optical properties and intrinsic stress of Ta2O5 thin films deposited by dual ion beam sputtering (DIBS) were studied as a function of the assist ion beam voltage (250–650 V). When the assist ion beam voltage was in the range of 350–450 V, the transmittance at the quarter-wave point reached its highest value (lowest absorption). The refractive index increased to 2.185 as the assist ion beam voltage increased from 250 to 350 V, but decreased as the assist ion beam voltage was further increased from 350 to 650 V.

Diastereoselective germastannylation of bis(allenes) with germylstannanes, catalyzed by palladium complexes, for the construction of cis or trans five-membered cyclic systems has been investigated. We observed that the relative stereochemical arrangements of the reaction products depends on the substituents in the reagents containing Ge−Sn σ-bonds. When the reagent Ph3GeSnBu3 was employed in the Pd0-catalyzed carbocyclization of bis(allenes), trans-cyclized products and/or cis-fused bicyclic dienes were produced. In contrast, cis cyclic compounds were obtained, again along with cis-fused bicyclic dienes, from the reaction with Bu3GeSnBu3. NMR experiments to establish the stereochemical relationships and a mechanistic speculation for this transformation as a possible explanation for the different stereochemical outcomes are also described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

[reaction: see text] A new procedure for the synthesis of cis-2-triethylsilylvinyl-cyclopentanols and -cyclohexanols from allenyl-aldehydes and -ketones with Et(3)SiH through rhodium-catalyzed silylative carbocyclization is described. The use of Rh(acac)(CO)(2) (1 mol %) to promote the reaction results in a mild and convenient protocol for the three-component assembly.

Treatment of allenyl-aldehyde dimethyl acetals with iodotrimethylsilane, titanium tetrachloride, and indium trichloride afforded a mixture of separable cis- and trans-2-haloalkenyl substituted 2-haloalkenylcycloalkyl methyl ethers by intramolecular nucleophilic attack of allene moiety to the oxonium ion generated by the reaction of TMSI, TiCl4, or InCl3 to dimethyl acetal moiety.

Regio- and stereoselective radical addition of α-allenic alcohols with p-TsBr in the presence of a catalytic amount of AIBN afforded (E)-γ-bromo-β-sulfonyl allylic alcohols in moderate yields. The base-promoted 1,4-elimination followed by isomerization to give β-sulfonyl-α,β-unsaturated ketones is described.

Indium-mediated allylation of 1,2-dicarbonyl compounds with indium and allylic bromides was achieved in the presence of nBu4NI or NH4Cl as additive to afford mono- and/or diallylated products in good yields.

The copper-catalyzed N-arylation of benzamides or nitrogen heterocycles was carried out with catalytic CuI (10 mol%) in the presence of ethylenediamine (10 mol%) as a ligand and K 3 PO 4 or Cs 2 CO 3 as a base under mild conditions.

[reaction: see text] alpha-Allenic sulfonamides undergo carbonylation-coupling-endo-cyclization with aryl iodides in the presence of Pd(PPh(3))(4) (5 mol %), K(2)CO(3), and CO (20 atm) to form 3-aroyl-2- or 3-pyrrolines. Alternatively the carbonylation-coupling-exo-cyclization of gamma- and delta-substituted sulfonamides under the same conditions afforded pyrrolidine- or piperidine-substituted enones.

The palladium-catalyzed carbon-carbon bond formation of organolead(IV) triacetates with terminal alkynes was accomplished with Pd2(dba)3·CHCl3 (5 mol%) and CuI (10 mol%) in the presence of NaOMe (2 equiv.) in MeOH/CH3CN (1:1) at room temperature.

The palladium-catalyzed cross-coupling of hypervalent iodonium salts with organobismuth(V) derivatives was accomplished with PdCl2 (5 mol%) in CH3CN at room temperature.

Treatment of alkynylsilanes with triarylantimony diacetates in the presence of Pd2(dba)3·CHCl3 (5 mol%) and CuI (10 mol%) in CH3CN at 50 °C for 5 h afforded aryl-substituted alkynes in good yield. Alternatively, direct carbonylative coupling of triarylantimony diacetates with alkynylsilanes was accomplished under atmospheric pressure of carbon monoxide.

The palladium-catalyzed cross-coupling of hypervalent iodonium salts with organotellurium dichloride was achieved with PdCl2 (10 mol %) in the presence of NaOMe (3 equiv) in CH3CN/MeOH at room temperature.

The palladium-catalyzed cross-coupling and carbonylative cross-coupling of pentavalent bismuth(V) derivatives with organostannanes have been achieved in CH3CN at room temperature.

The palladium-catalyzed arylation reaction of vinyl epoxides with organobismuth compounds afforded the aryl-substituted (E)-allylic alcohols via ring opening of epoxides. Alternatively, the palladium-catalyzed reaction of diol acetonides and carbonates with bismuth derivatives afforded the aryl-substituted diol acetonides and carbonates without ring opening.

Organolead acetates can be carbonylated in the presence of Pd2(dba)3·CHCl3 (5 mol%) and NaOMe (5 equiv.) in CH3CN under atmospheric pressure of carbon monoxide at room temperature to afford symmetrical ketones.

Triarylstibines react with iodobenzene diacetate in dichloromethane to afford triarylantimony(V) diacetates. The cross-coupling and carbonylative cross-coupling of triarylantimony(V) diacetates and dichlorides with organostannanes was accomplished in the presence of PdCl 2 (5 mol%) in CH 3 CN at room temperature.

The palladium Pd(PPh3)4-catalyzed coupling reaction of allenyl N-tosylcarbamates with hypervalent iodonium salts afforded the cyclized trans-5-substituted oxazolidinones, 3-oxazin-2-ones, and higher membered carbamates under mild conditions.

The Stille coupling of (Z)-1,2-bis(trimethylstannyl)ethenes with hypervalent iodonium salts (1 equiv) proceeded stereospecifically in the presence of PdCl2 (5 mol %) in DMF at room temperature to afford partially substituted (Z)-vinylstannanes under mild conditions. Alternatively, the use of 2 equivalents of hypervalent iodonium salts afforded tri-substituted alkenes.

The palladium-catalyzed cross-coupling of (η6 -chlorobenzene) tricarbonylchromium complexes with organofluorosilanes followed by decomplexation afforded aryl-, alkenyl-, and alkynyl-substituted arenes.

Palladium-catalyzed cross-coupling of hypervalent iodonium salts with polymer bound alkene, alkyne, and boronate was achieved under mild conditions.

Four stereoisomers of muricatacin 1a-d were prepared by the reaction of corresponding aldehydes 4a-d, which in turn were prepared from D-glucose, with the anion of triethylphosphonoacetate followed by reduction and cyclization under acidic conditions. Cytotoxicities of four stereoisomers were tested against in vitro A-549 cell line as well as MCF-7 cell line. Stereochemistry at C4 and C5 position of muricatacin did not affect the cytotoxicities significantly.

Pd(0)-catalyzed arylation of the aryl-substituted α-allenic alcohols with hypervalent iodonium salts afforded substituted trans-epoxides. Alternatively, arylation of the alkyl-substituted α-allenic alcohols in the presence of K 2 CO 3 afforded syn-diol cyclic carbonates and trans-epoxides in the presence of Cs 2 CO 3 .

The cross-coupling reaction of organoboronic acids and carbon monoxide (1 atm) with aryl-, alkenyl-, and alkynyliodonium salts at room temperature afforded unsymmetric aromatic ketones in moderate yields.

The ligand coupling of various diaryl- or alkynyl(phenyl)iodonium salts in the presence of diethylzinc and a palladium catalyst afforded biaryls or dialkynes under mild conditions.

The palladium- and copper-catalyzed dimerization of aryl- and alkynyllead triacetates to form biaryls and dialkynes under mild conditions is described.

Arylation and alkenylation of 1-ethoxy-1-trimetylsilyloxycyclopropane with diphenyliodonium tetrafluoroborate and alkenyliodonium tetrafluoroborate were accomplished by slow addition of silyloxycyclopropane to iodonium salts in the presence of Pd(OAc)2 (2 mol %) and DME H 2 O (4:1) to afford β-substituted ester. Alternatively, carbonylative coupling of silyloxypropane was carried out by slow addition of silyloxypropanes to iodonium salts under CO(1 atm) at room temperature in aqueous medium. The palladium-catalyzed coupling of ketene trimethylsilyl acetals with iodonium salts is also described.

The palladium-catalyzed cross-coupling of organostannanes with iodonium salts in the presence of PdCl2(0.5 mol %) or Pd/C(2 mol %) as Pd(O) source was accomplished at room temperature under aqueous conditions.

The hetero-cross coupling reaction of diphenyliodonium tetrafluoro-borate with secondary amine in the presence of LiNTMS2 or NaOtBu as base, Pd2(dba)3°CHCl3 as catalyst, and tri-o-tolylphosphine as ligand afforded arylamines at room temperature under mild conditions.

Allylic substitution of allylic cyclic carbonates with PhSH or PhOH in the presence of CpRu(PPh3)2Cl (5 mol %) afforded (E)-allylic alcohol and erythro-β-hydroxy thiophenoxide or phenoxide respectively, via external attack of nucleophiles to π-allyl ruthenium complex.

The palladium-catalyzed coupling of organostannanes with iodanes(Koser's and Zefirov's reagents) in the presence of palladium catalyst was accomplished at room temperature under aqueous conditions to afford phenyl- or 4-iodophenyl-substituted products depending on the iodanes used.

Allylation of aldehydes by reaction allylic phosphates with diethylzinc in the presence of Pd(PPh3)4 afforded homoallylic alcohol via nucleophilic allylzinc species.

RuH2(PPh3)4-catalyzed reductive cleavage reactions of chiral allylic cyclic carbonates with ammonium formate afforded optically active (E)-allylic alcohols with excellent regioselectivity. Alternatively, hydrogenolysis of propargylic cyclic carbonates in the presence of RuH2(PPh3)4 catalyst afforded allenic alcohols as a sole products.

Palladium-catalyzed arylation of allylic cyclic carbonates with iodobenzene in the presence of Pd(OAc), as catalyst afforded the phenyl-substituted allylic alcohols via palladium oxygen β-elimination. However, palladium-catalyzed arylation, alkenylation, and alkynylation of allylic cyclic carbonates with iodonium tetrafluoroborates afforded the phenyl, alkenyl, and alkynyl-substituted allylic cyclic carbonates without reductive ring opening under aqueous and nouaqueous conditions.

The coupling reaction of iodobenzene with allylic diols in the presence of Pd(OAc) 2 and n Bu 3 P as catalysts using K 2 CO 3 as base afforded the phenyl-substituted allylic diols. However, under the same reaction conditions with Et 3 N as base, phenyl-substituted α-hydroxy ketone was obtained.

Reaction of chiral allylic cyclic carbonates with Grignards reagent in the presence of NiCl2(dppe) as a catalyst afforded the alkylated (E)-allylic alcohols with high regio- and diastereoselectivity.

Palladium(O)-catalyzed allylation of aldehydes by allylic cyclic carbonates with SnCl2 proceeded smoothly to afford 1,3-diols with high diastereocontrol. For the exomethylene cyclic carbonate, allylation with aldehydes furnished 1,4-diols or 1,5-diols depending on amount of aldehydes.

Porcine pancreas lipase(PPL)-catalyzed acetylation of (±)-2-hydroxymethyl-3,4-dihydro-2 H -pyran with vinyl acetate in organic solvent afforded ( S )-(+)-2-acetoxymethyl-3,4-dihydro-2 H -pyran. Alternatively, (±)-2-acetoxymethyl-3,4-dihydro-2 H -pyran was resolved via hydrolysis catalyzed by PPL in acetone-phosphate buffer system to afford ( S )-(+)-2-hydroxymethyl-3,4-dihydro-2 H -pyran with high enantiomeric purity.

The alkyl substituted allylic cyclic carbonates 1a-d undergo elimination by using a catalytic amount of Pd(0) complex to form dienols 2a-b . However, on treatment of the unsubstituted or phenyl substituted allylic cyclic carbonates 1e and 1f with palladium(0) catalyst, deprotonation-elimination of π-allylpalladium complex followed by condensation with the other π-allylpalladium complex provided the coupled products 3a and 3b , respectively.

Treatment of chiral allylic cyclic carbonates with ammonium formate in the presence of Pd(0) catalyst afforded optically active homoallylic alcohols with excellent regioselectivity. However, hydrogenolysis of dienylic cyclic carbonates in the presence of Pd(0) catalyst afforded conjugated or nonconjugated (E)-dienylic alcohols depending on Pd complexes used. Using homoallylic alcohol 3c as a chiral synthon, (R)-(+)-eldanolide, the sex pheromone of the African sugarcane stem borer, Eldana saccharina, was synthesized.

Reaction of chiral allylic and dienylic cyclic carbonates with various nucleophiles in the presence of (PPh 3 ) 4 Pd as a catalyst afforded α-, γ-, or e-substituted products with high regio-, ( E )-stereo-, and diastereoselectivity depending on nucleophiles.

The palladium-catalyzed acylation reaction of alkenoyl- and alkanoylzirconocene chlorides with hypervalent iodonium salts afforded the acylated aromatic compounds under mild conditions.

Treatment of α,β-dihydroxy ketones with carbonyldiimidazole resulted in the formation of α-diketones based on the elimination of the cyclic carbonates formed in situ.

A practical and enantiospecific method for the synthesis of optically pure allylic alcohols [(R)- or (S)-1-alken-3-ols] is described. The key reaction is the reductive cleavage of the cyclic carbonates of 1-halo-2,3-alkanediols with zinc, magnesium, or samarium diiodide.

Reaction of the cyclic carbonates of acyclic vinyl diols with RCu(CN)Li· BF 3 , RCu(CN)MgBr·BF 3 , or RMgBr·CuI (cat) in THF at −78 °C proceeded in S N 2′ fashion and resulted in the formation of alkylated ( E )-allylic alcohols with remarkably high diastereoselectivity. This reaction represents an efficient 1, 3-chirality transfer method.