Manganese-catalyzed oxidative homo-coupling of aryl Grignard chlorides

Manganese-catalyzed homo-coupling of aryl magnesium chlorides to give biphenyls was successfully achieved using manganese chloride as catalyst. A variety of aryl magnesium chlorides were efficiently converted into the corresponding symmetrical biaryls using 10 mol% MnCl₂ as catalyst in the presence of a stoichiometric amount of 1,2-dichloroethane. Since the aryl chlorides, from which the Grignard reagents were prepared, are cheaper and more readily available that the corresponding bromides and iodides this procedure should become the method of choice for preparing symmetrical biaryls.     

Iron-catalyzed oxidative homo-coupling of aryl Grignard reagents

[reaction: see text] Iron-catalyzed homo-coupling of aryl Grignard reagents was successfully developed. A variety of aryl Grignard reagents were efficiently converted into the corresponding symmetrical biaryls in the presence of 1-5 mol % FeCl3 and a stoichiometric amount of 1,2-dichloroethane.     

温和条件下钒催化氧化胺、醇和胺直接合成亚胺(英文)

开发了钒催化氧化胺、醇和胺直接合成亚胺催化体系,无须额外的添加剂或促进剂,空气作为环境友好的氧源,温和条件下,能高收率地得到各种对称和非对称亚胺,并且催化剂非常容易制备和使用.该催化体系对含杂原子亚胺的合成也非常有效.     

Tellurium(IV) tetrachloride catalysed facile knoevenagel reaction

Non-enolisable aldehydes (I) and active methylene compounds (II) react in the presence of tellurium(IV) tetrachloride (catalytic) to give the corresponding α, β-unsaturated carbonyl compounds (III) in excellent yields and high purity.     

Sodium nitrite catalyzed aerobic oxidative deoximation under mild conditions

A mild, simple process for the effective deoximation of a wide range of ketoximes and aldoximes has been developed, which utilizes available NaNO(2) as the catalyst and molecular oxygen as the green oxidant. Notably Amberlyst-15, which acts as the initiator of NaNO(2), can be reused without regeneration. This environmentally benign protocol could provide a valuable synthetic method for practical applications.     

Selective,iron pentacarbonyl catalyzed reduction of aryl iodides under mild conditions

Potassium tetracarbonylhydridoferrate, generated in situ from Fe(CO)₅/K₂CO₃ in methanol has been found to bring about catalytic reduction (up to 18 cycles) of aryl iodides under 1 atm carbon monoxide pressure. This reagent is specific for iodoaromatics, and tolerates the presence of several functionnal groups.     

Palladium catalyzed alkynylation of aryl halides (Sonogashira reaction) in water

The palladium catalyzed alkynylation of aryl halides (Sonogashira reaction) has been achieved in pure water without any additives or phase transfer catalysts. The reaction, which requires only 0.5 mol % of Pd(PPh₃)₄ catalyst, is remarkably fast (30 min at 70 °C) producing high yields of the aryl alkyne products.     

Enantioselective pinacol coupling of aryl aldehydes catalyzed by chiral Salan-Mo(IV) complexes

Reported herein is the asymmetric pinacol coupling of aromatic aldehydes with chiral Salan-Mo(VI) dioxo complex as an effective precatalyst. Chiral diols were obtained with high diastereoselectivity and enantioselectivity up to 92/8 and 95%, respectively. The possible mechanism of the pinacol coupling reaction with the catalytic system was investigated. The X-ray crystal structure of the precatalyst Mo(L3)O2 was determined and the oxidation state of the intermediate C was confirmed as +4 with X-ray photoelectron spectroscopy study. The proposed mechanism speculated the stereochemical outcome of the reaction, and a working model for the radical coupling of E was proposed, which explained the absolute configuration of the favored (S,S)-enantiomer of the dl isomer.     

Palladium(II)-catalyzed oxidative homo-coupling of 1,3-dimethyluracil derivatives

A palladium-catalyzed oxidative homo-coupling of 1,3-dimethyluracil was examined. Two types of uracil dimer, C5–C5′ linked dimer and C5–C6′ linked dimer were obtained in variable yields depending on the conditions along with a low yield of C5–C5′ and C6–C5′ linked uracil trimer.     

Novel oxidation of toluenes catalyzed by reusable vanadyl(IV) sulfate under mild conditions with molecular oxygen

Efficient oxidation system using reusable vanadyl(IV) sulfate catalyst was established. Toluenes were easily oxidized under molecular oxygen (0.1 MPa) at 100 °C catalyzed by vanadyl(IV) sulfate to afford the corresponding benzoic acids in excellent yields. The recovered catalyst could be reused without loss of activity.     

Palladium-catalyzed denitrogenative cross-coupling of aryl halides with arylhydrazines under mild reaction conditions

Transition Metal Chemistry - A greener approach for the synthesis of various functionalized biaryl frameworks in good to excellent yield through palladium-catalyzed denitrogenative cross-coupling...     

Bis‐benzimidazolium‐palladium system catalyzed Suzuki‐Miyaura coupling reaction of aryl bromides under mild conditions

Bis‐benzimidazolium salts were prepared successfully from commercially available and inexpensive o‐phenylenediamine through a series of simple reactions. The bis‐NHC‐Pd complexes prepared in situ can catalyze Suzuki‐Miyaura cross‐coupling reaction under very mild conditions in aqueous media with excellent yields. The efficiency of this reaction is demonstrated by its compatibility with a range of functional groups. Di‐ortho‐substituted biaryls could be accomplished in 89–99% yields. Moreover, the rigorous exclusion of air or moisture is not required in these transformations.     

Nickel‐catalyzed oxidative esterification of formamides with 1,3‐dicarbonyl compounds under mild reaction conditions

Synthesis of enol carbamates was achieved via nickel‐catalyzed oxidative coupling of formamides with 1,3‐dicarbonyl compounds in the presence of tert ‐butyl hydroperoxide at 40 °C. Various derivatives of enol carbamates were synthesized by this method in good to excellent yields.     

Oxidative homo-coupling of potassium aryltrifluoroborates catalyzed by gold nanocluster under aerobic conditions

Gold(0) nanoclusters, stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP-n), catalyzed the oxidative homo-coupling reaction of potassium aryltrifluoroborate in water under air. Catalytic activity was dependent on the size of clusters. The smallest cluster Au:PVP-1 (d_av = 1.3 ± 0.3 nm) gave the highest activity, while Au:PVP-7 (d_av = 9.5 ± 1.0 nm) did not catalyze the homo-coupling. The catalyst was reusable for several times. Positively charged surface on the Au cluster, generated by the adsorption of molecular oxygen, would be the active site of the catalysis.     

Amperometrische Bestimmung von Vanadium(IV) und Titan(IV)

Ohne Zusammenfassung     

Zur Bestimmung von Vanadium(IV)

Ohne Zusammenfassung     

Palladium-catalyzed oxidative carbonylation of alkyl and aryl indium reagents with CO under mild conditions

CO now can react with organoindium reagents. A novel palladium-catalyzed oxidative carbonylation reaction of organoindium reagents by CO gas with desyl chloride as oxidant was developed in supplementation with the classical methods for preparation of carboxylic acid derivatives. Primary, secondary alkyl indium reagents with beta-hydrogens and aryl indium reagents were suitable substrates, and the reaction could be carried out at 60 degrees C under 50 psi CO. Carbonylation of alkyl indium reagents can occur smoothly without additional base. Although the indium reagents were prepared from corresponding Grignard reagents (at low temperature), they displayed full compatibility with various functional groups under the protic reaction conditions. Preliminary mechanistic studies including stoichiometric and catalytic reaction examination provided evidence to support the operation of the mechanism consisted of oxidative addition of deslyl chloride to Pd(0) and quick tautomerization to give a palladium enolate species II (ROPdCl), displacement of the enolate group in II by R(2)OH, followed by CO insertion to give alkoxycarbonyl palladium complex V, which undergoes transmetalation with R(1)(3)In and reductive elimination to afford the product and a Pd(0) species. In this mechanism, the alkoxycarbonyl group was transferred to the palladium center prior to the alkyl group, different from traditional ways initiated from oxidative addition of alkyl halides to a Pd(0) species.     

An efficient intermolecular C(aryl)-S bond forming reaction catalyzed by BINAM-copper(II) complex

A wide range of diaryl thioethers and aryl alkyl thioethers are synthesized from the corresponding aryl iodides and aromatic/aliphatic thiols through Ullmann type intermolecular coupling reactions in the presence of a catalytic amount of easily available BINAM-Cu(OTf)₂ complex. Less reactive aryl bromides have also been shown to react with thiols under identical reaction conditions to give good yields of the thioethers without increasing the reaction temperature and time.