Catalytic enantioselective carboncarbon bond formation by addition of dialkylzinc reagents to cyclic 1,3-diene monoepoxides

Chiral copper complexes of 2,2′-binaphthyl-based phosphorus amidites are shown to be highly effective catalysts for the conjugate addition of dialkylzinc reagents to vinyloxiranes. The corresponding allylic alcohol reaction products (S_N2′-pathway) were obtained with moderate to high regioselectivity. Both direct- (S_N2-pathway) and conjugate-opening addition (S_N2′-pathway) seem to proceed with complete anti stereoselectivity. The enantioselectivity of these addition reactions according to a kinetic resolution protocol turned out to be high (>90% ee) with 1,3-cyclohexadiene and 1,3-cycloheptadiene monoepoxides.     

Electrochemical studies on organometallic compounds: XXVIII. Catalysis of the electrochemical reduction of benzyl chloride by niobium(III) anionic complexes and formation of carboncarbon bonds

The dicyclopentadienylniobium(III) dichloride anion has been shown to be an effective catalyst for the electrochemical reduction of benzyl chloride. Indirect cathodic reduction yields diphenylethane.     

Ring-opening of cyclic ethers with carbon–carbon bond formation by Grignard reagents

The ring-opening of cyclic ethers with concomitant C–C bond formation was studied with a number of Grignard reagents. The transformation was performed in a sealed vial by heating to ∼160 °C in an aluminum block or at 180 °C in a microwave oven. Good yields of the product alcohols were obtained with allyl- and benzylmagnesium halides when the ether was tetrahydrofuran or 3,3-dimethyloxetane. Lower yields were obtained with substituted tetrahydrofurans while no ring-opening was observed with tetrahydropyran. Only highly reactive allyl and benzyl Grignard reagents participated in the transformation while no reaction occurred with other alkylmagnesium halides.     

Iridium pentahydride complex catalyzed formation of CC bond by CH bond activation followed by olefin insertion

The formation of carbon-carbon bond was found to occur by first carbon-hydrogen bond activation followed by olefin insertion under the catalysis of an iridium pentahydride complex.     

Efficient carboncarbon bond formation with thermally stable 1,1-dihalo-2,2,2-trifluoroethylzinc reagent

The zinc carbenoids CF₃CX₂ZnX, prepared from CF₃CX₃ and zinc powder in dimethylformamide, were found thermally stable to add to aldehyde carbonyls in excellent yields.     

Rhodium-catalyzed CC bond formation by ring-opening of alkylidenecyclopropanes and insertion of 3-butenoic acid

Diphenylmethylenecyclopropane reacts with 3-butenoic acid in the presence of RhCl(PPh₃)₃ to give products resulting from insertion of one or two molecules of butenoic acid. Insertion of the first molecule of butenoic acid is not regioselective, whereas insertion of the second is highly regioselective.     

Novel oxidative cleavage of carbon—carbon bond in hydrazones by oxygenation with cobalt Schiff base complex

Oxygenation of aromatic ketone hydrazones with Co(salen) in methanol resulted unexpectedly in oxidative degradation to give methyl benzoate derivatives. A mechanism involving nucleophilic attack by methanol on a diazo intermediate is discussed.     

Air-stable P-stereogenic secondary phosphine oxides as chiral monodentate ligands for asymmetric catalytic carboncarbon bond formation

P-Stereogenic secondary phosphine oxides are configurationally stable in the presence of metal ions both in solution and in the solid state. They have the potential to serve as chiral monodentate phosphorus ligands for asymmetric catalysis. In the asymmetric allylic alkylation of 1,3-diphenylprop-2-enyl acetate, ca. 80% ee was achieved using (R_p)-tert-butylphenylphosphine oxide.     

Allyldialkyl complexes of ruthenium(IV): Preparation and reductive CC bond formation followed by CH bond activation

New η³-allyldimethyl complexes Ru(η⁵-C₅R₅)(η³-C₃H₅)(CH₃)₂, where R = H or CH₃, are prepared from Ru(η⁵-C₅R₅)(η³-C₃H₅)Br₂ by alkylation with trimethyl-aluminium. The Ru^IV dimethyl complex is thermally converted to the Ru^II 1-methylallyl compound, Ru(η⁵-C₅R₅)(η³-CH₂CHCHCH₃)L, where L = CO or t-C₄H₉NC, with evolution of methane. Kinetic and deuteration studies on the reductive process are also discussed.     

Nickel complex induced CC-linkage of carbon dioxide with trienes

Reaction fo (bipyridine)(1,5-cyclooctadiene)nickel with carbon dioxide and 1,3,7-octatriene yields products which indicate that the CO₂ attacks only at the diene part of octatriene. In the same reaction 1,3,5-hexatriene couples with CO₂ to yield 1/1, 1/2 and 2/2 adducts.     

Synthesis and spectroscopic studies of organotin compounds containing the SnS bond

The preparation of a number of organotin(IV) compounds, containing SnS bonds, is described. Their ¹³C and ¹H NMR and IR spectra are presented. In cases where either SnS or SnN may be expected, Mössbauer spectra show two sets of peaks consistent with these possibilities.     

Carbon–carbon bond formation via benzoyl umpolung attained by photoinduced electron-transfer with benzimidazolines

A photoreaction between benzoyl compounds, such as benzoylformate derivatives, and 2-(p-anisyl)-1,3-dimethylbenzimidazoline in the presence of allyl bromide was found to give various allylated alcohols. In the reaction of benzoylformates, α-hydroxy ester enolates, for which the negative charge occurs on the carbonyl carbon of benzoyl (umpolung reactivity), are proposed to be generated as intermediates by electron-transfer from benzimidazolines to the photoexcited benzoylformates; these species react with allyl bromide to produce α-allyl-α-hydroxy esters.     

Photosolvolysis of a carboncarbon bond. The photolysis of n,n-dimethyl- 2,2-diphenylethylamine in methanol.1

The title compound is photolyzed in methanol to give good yields (ca. 50%) of diphenylmethane indicating that the CC bond undergoes a formal heterolytic cleavage from the excited state as predicted from the measured redox potentials of the two ions.     

Investigation of lipase-catalyzed Michael-type carbon–carbon bond formations

Conjugate additions of carbon nucleophiles to appropriate acceptor molecules were investigated with respect to the synthetic potential and stereochemistry of the products. Reactions of short-chain α,β-unsaturated ketones and mono-substituted nitroalkenes with CH-acidic carboxylic ester derivatives were catalyzed by various immobilized lipases. Using methyl nitroacetate complete conversion with methyl vinyl ketone and trans-β-nitrostyrene was obtained. The reactions proceeded without enantioselectivity. Evidence for enzyme catalysis is provided by the observation that after denaturation of Candida antarctica lipase B or inhibition no reaction took place. Docking studies with the chiral addition product methyl 2-methyl-2-nitro-5-oxohexanoate did not reveal any specific binding mode for this reaction product, which would have been the requirement for stereoselective additions. These results support the experimental findings that the conjugate addition takes place without enantiopreference.     

Comparison of the magnetic properties of MmFeband NdFeB compounds

NdFeB and corresponding MmFeB compounds were studied, the high field magnetization at 4.2 K, the a.c. susceptibility (4.2 < T < 300 K) and the anisotropy field were measured using the singular point detection technique (77 < T < 570 K). At room temperature the anisotropy field of the MmFeB is about 3T, whereas that of NdFeB compounds is about 7T. The MmFeB compounds showed effects due to the cerium (lowering the Curie temperature) as well as due to the neodymium (spin reorientation at low temperatures).     

Carbon-carbon bond formation by radical addition of α-trifluoromethylacrylate with cyclic ethers

The radical addition reactivity of tert-butyl α-trifluoromethylacrylate (CH₂C(CF₃)COOC(CH₃)₃) (BFMA) with cyclic ethers was investigated in order to compare to that of perfluoroisopropenyl ester. One to one addition compound of BFMA with tetrahydrofuran (THF) was produced in fairy high yields in the presence of 2,2′-azobisisobutyronitrile, benzoyl peroxide or di-tert-butyl peroxide to give 2-substituted THF derivative. Time-conversion investigation showed much higher reactivity of BFMA compared to that of 2-benzoxypentafluoropropene [CF₂C(CF₃)OCOC₆H₅]. Radical additions of BFMA with 1,4-dioxane, 1,3-dioxolane and tetrahydropyran were also examined to afford corresponding 1:1 addition products in fairly high yields by achieving carbon-carbon bond formation. It is then concluded that no interconversion of fluoroalkylcarbon radical and hydrocarbon radical may take place in the reaction system of BFMA which possesses two less fluorines in the vinyl group compared to 2-benzoxypentafluoropropene. The method may be a facile way to prepare trifluoromethyl-substituted organic compounds accompanied by the formation of carbon-carbon bonds by the aid of fluorine atoms.     

Carbon—carbon and carbon—nitrogen bond formation reactions catalyzed by the magnesium and calcium acenaphthene-1,2-diimine complexes

A mixture of allylbromide and diphenylacetonitrile is reduced to afford 2,2-diphenylpentene-4-nitrile as a major product in the presence of catalytic amounts of the magnesium complex (dpp-bian)Mg(thf)3 (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion). The overall conversion of nitrile is 71% within 3 h at 85 °С. 4,4-Diphenylbutene-1 and diphenylmethane are by-products in this process. Complexes (dpp-bian)Mg(thf)₃ and (dpp-bian)Ca(thf)₄ (in an amount of 0.5—5 mol.%) catalyze the intramolecular hydroamination of some aminopentenes and aminohexenes with the conversion from 67 to 99%.     

Protonation of (μ-H)3Ru3(μ3-CR)(CO)9. Evidence for the formation of an agostic metalhydrogencarbon bond

Protonation of (μ-H)₃M₃(μ₃-CR)(CO)₉ (M = Ru, R = Et or M = Os, R = Me) by dissolution in HSO₃CF₃ yields H₃M₃(HCR)(CO)₉⁺, containing a MHC bridge. The products were characterized by ¹H and ¹³C NMR spectroscopy. Decompositions of other protonated methylidyne clusters from CH₃R and a variety of metal-containing products.     

The highly chemoselective transfer hydrogenation of the carbon–carbon double bond of conjugated nitroalkenes by a rhodium complex

Chemoselective transfer hydrogenation of conjugated nitroalkenes catalyzed by [RhCl₂Cp¹]₂–diamine complex (Cp¹=η⁵-C₅Me₅) using HCOOH/Et₃N (5:2) (TEAF) as a hydrogen source was realized. A variety of nitrostyrenes, β-methyl nitrostyrenes, and 3-methyl-4-nitro-5-alkenyl-isoxazoles were reduced smoothly in good to excellent yields in short reaction time. Other functional groups are inert under the reaction conditions.