Copper-catalyzed extended Pummerer reactions of ketene dithioacetal monoxides with alkynyl sulfides and ynamides with an accompanying oxygen rearrangement.

The first examples of metal-catalyzed extended Pummerer reactions through the activation of sulfoxides are described. The copper-catalyzed reactions of ketene dithioacetal monoxides with alkynyl sulfides and ynamides provided a wide variety of γ,γ-disulfanyl-ß,γ-unsaturated carbonyl compounds with an accompanying oxygen rearrangement. The products can be easily converted into 1,4-dicarbonyl compounds and substituted heteroaromatics. DFT calculations and mechanistic experiments revealed a new interesting stepwise addition/oxygen rearrangement mechanism.

Synthesis of alkylidenecyclopropanes by palladium-catalyzed reaction of propargyl-substituted malonate esters with aryl halides by anti-carbopalladation pathway.

Palladium-catalyzed arylative cyclization of propargyl-substituted malonate esters with aryl halides offers a stereoselective approach to alkylidenecyclopropanes. The reaction proceeds by an anti-carbopalladation pathway, which guarantees the exclusive stereocontrol of the resulting double bond. The highly strained as well as densely substituted skeletons of the products facilitate further versatile transformations, which underscores the importance of the products as synthetic intermediates.

Rhodium-catalyzed arylzincation of terminal allenes providing allylzinc reagents and its application to versatile three-component coupling reaction.

Rhodium-catalyzed regioselective arylzincation of terminal allenes affords synthetically useful functionalized allylzinc reagents. The allylzinc reagents react with a variety of electrophiles such as acetonitrile, offering a more versatile three-component coupling reaction.

Synthesis of 3-trifluoromethylbenzo[b]furans from phenols via direct ortho functionalization by extended Pummerer reaction.

A concise and diversity-oriented route to trifluoromethylbenzo[b]furans has been devised. A variety of phenols are directly converted to the corresponding 2-methylthio-3-trifluoromethylbenzo[b]furans by new triflic-anhydride-mediated extended Pummerer annulation reactions with trifluoromethylketene dithioacetal monoxide. The methylthio group of the products undergoes further transformations, which increase the diversity of available trifluoromethylbenzo[b]furans.

Reaction pathway of methylenation of carbonyl compounds with bis(iodozincio)methane.

About 40 years have passed since methylene dizinc reagent was discovered as a substitute for Wittig reagent. Density functional theory (DFT) calculations have been performed to understand the reaction pathways of methylenation of carbonyl compounds with bis(iodozincio)methane. The present computational/theoretical study concluded that the methylenation reaction with gem-dizinc reagent proceeds as a two-step reaction, that is, methylene addition (RDS) and olefination. In the first step, the nucleophilic attack of the CH2 group enhanced by two Zn proceeds under the assistance of the electrophilic activation of the carbonyl group with the Zn atom. In the second step, the olefination is facilitated by both Zn atoms of the gem-dizinc reagent without an electron transfer process.

Palladium-catalyzed allylation of aryl halides with homoallyl alcohols bearing a trisubstituted double bond: application to chirality transfer from hydroxylated carbon to benzylic one.

A facile route to homoallyl alcohols bearing a trisubstituted double bond has been devised. The palladium-catalyzed reactions of aryl halides with the alcohols thus synthesized result in regiospecific allyl transfer from the alcohols to aryl halides via retro-allylation, providing allylarenes having two substituents at the 1 and 2 positions of the allyl moiety. Optically active homoallyl alcohols transfer their chirality at the hydroxylated carbon to the benzylic carbon of the product.

Synthesis of epoxides by palladium-catalyzed reactions of tertiary allyl alcohols with aryl or alkenyl halides.

A novel synthetic method for the preparation of tri- or tetrasubstituted epoxides is reported. Treatment of readily available tertiary allyl alcohol with aryl or alkenyl halide under palladium catalysis resulted in arylative cyclization to form the epoxide. The reaction includes intramolecular C-O bond and intermolecular C-C bond construction.

Nickel-catalyzed borylation of aryl cyclopropyl ketones with bis(pinacolato)diboron to synthesize 4-oxoalkylboronates.

Aryl cyclopropyl ketones undergo nickel-catalyzed borylative ring opening with bis(pinacolato)diboron to yield 4-oxoalkylboronates.

Palladium-catalyzed preparation of silyl enolates from alpha,beta-unsaturated ketones or cyclopropyl ketones with hydrosilanes.

Alpha,beta-unsaturated ketones and cyclopropyl ketones undergo palladium-catalyzed hydrosilylation with hydrosilanes to yield (Z)-silyl enolates.

Zinc-catalyzed nucleophilic substitution reaction of chlorosilanes with organomagnesium reagents.

Zinc-catalyzed nucleophilic substitution reactions of chlorosilanes with organomagnesium reagents afford various tetraorganosilanes under mild reaction conditions. The reactions can be performed on large scale and allow efficient preparation of functionalized tetraorganosilanes.

Synthesis of arylallenes by palladium-catalyzed retro-propargylation of homopropargyl alcohols.

Treatment of tertiary homopropargyl alcohol with aryl halide under palladium catalysis provided arylallenes regioselectively. The reaction includes retro-propargylation, which proceeds in a concerted fashion via a cyclic transition state and transfers the stereochemistry of homopropargyl alcohols through C-C bond cleavage. The present method enables the use of homopropargyl alcohols as allenylmetal equivalents.

Cobalt-catalyzed regioselective dehydrohalogenation of alkyl halides with dimethylphenylsilylmethylmagnesium chloride.

Cobalt-catalyzed reactions of haloalkanes with dimethylphenylsilylmethylmagnesium chloride result in highly regioselective dehydrohalogenation. The reaction does not follow the conventional E2 elimination mechanism but includes beta-hydride elimination from the corresponding alkylcobalt intermediate. The interesting reaction mechanism of the cobalt-catalyzed dehydrohalogenation offered unique transformations that are otherwise difficult to attain.

Palladium-catalyzed formal cycloaddition of silacyclobutanes with enones: synthesis of eight-membered cyclic silyl enolates.

Treatment of silacyclobutanes with enones under palladium catalysis resulted in formal cycloaddition to yield the corresponding eight-membered ring. The reaction provides a facile and convergent access to synthetically useful eight-membered cyclic silyl enolates.

Regio- and stereoselective hydroamidation of 1-alkynylphosphine sulfides catalyzed by cesium base.

Regio- and stereoselective hydroamidation of 1-alkynylphosphine sulfides proceeds in the presence of cesium carbonate to provide (E)-2-amino-1-thiophosphinyl-1-alkenes. Asymmetric hydrogenation of the adducts catalyzed by an iridium complex followed by desulfidation yields 2-amino-1-phosphinoalkanes, which offers a new approach to chiral N,P-ligands that will potentially serve as ligands in asymmetric reactions.

Intermolecular radical addition of alkylthio- and arylthiodiphenylphosphines to terminal alkynes.

Intermolecular radical thiophosphination of terminal alkynes with alkylthio- and arylthiophosphines affords 1-thio-2-phosphino-1-alkenes in good yields. The addition reaction proceeds predominantly in an anti fashion to yield E isomers.

Nickel-catalyzed allylation of allyl carbonates with homoallyl alcohols via retro-allylation providing 1,5-hexadienes.

A highly efficient and mild method for the synthesis of 1,5-hexadienes, nickel-catalyzed reactions of Boc-protected allyl alcohols with homoallyl alcohols, has been developed. Nickel-mediated retro-allylation allows for the use of homoallyl alcohols as allylmetal equivalents in the synthesis of 1,5-hexadienes.

Nickel-catalyzed carboxylation of organozinc reagents with CO2.

An efficient nickel catalyst system for the carboxylation of organozinc reagents with CO(2) under very mild conditions has been developed. The catalyst system complements the conventional methods and enables the direct synthesis of various saturated carboxylic acid derivatives from the corresponding alkylzinc reagents and CO(2).

Copper-catalyzed reaction of alkyl halides with cyclopentadienylmagnesium reagent.

Treatment of alkyl halides, including tertiary alkyl bromides, with cyclopentadienylmagnesium bromide in the presence of a catalytic amount of copper(II) triflate yielded the corresponding cyclopentadienylated products in high yields. The following hydrogenation of the products provided alkyl-substituted cyclopentanes.

Silver-catalyzed benzylation and allylation reactions of tertiary and secondary alkyl halides with grignard reagents.

Treatment of alkyl halides, including tertiary alkyl bromides, with benzylic or allylic Grignard reagent in the presence of a catalytic amount of silver nitrate in ether yielded the corresponding cross-coupling products in high yields. The coupling reactions of tertiary alkyl halides provide efficient access to quaternary carbon centers.

Nickel-catalysed reactions with trialkylboranes and silacyclobutanes.

Nickel catalysis enables us to develop new reactions with trialkylboranes and silacyclobutanes of modest reactivity. A combination of Ni(cod)(2) and tri-tert-butylphosphine catalyses alkylation reactions of aldehydes and alpha,beta-unsaturated esters with various trialkylboranes of modest reactivity, suppressing conceivable beta-hydride elimination from alkylnickel intermediates. A nickel catalyst is also useful for 1,4-addition of bis(pinacolato)diboron to alpha,beta-unsaturated esters and amides. Nickel-catalysed reaction of silacyclobutanes with aldehydes results in ring opening to afford the corresponding alkoxyallylsilanes. In contrast, the ring expansion reaction of benzosilacyclobutene with aldehydes yields benzoxasilacyclohexenes. A nickel catalyst prepared from Ni(cod)(2) and tricyclohexylphosphine realises direct silylation of terminal alkenes with silacyclobutane furnishing vinylsilanes.