G. A. Artamkina

Palladium-catalyzed reaction of aryl halides with ureas

A new method for the palladium-catalyzed arylation of ureas is described. The coupling reaction of urea and phenylurea with aryl halides containing electron-withdrawing groups in the p-position in dioxane in the presence of 0.5–1.0 mol% of Pd2dba3·CHCl3, Xantphos and Cs2CO3 as a base gives N,N′-diarylureas in yields of 64–92%.

Variation of xanthene-based bidentate ligands in the palladium-catalyzed arylation of ureas

A series of xanthene-based bidentate ligands containing various substituents on diphenylphosphino groups were synthesized and tested in the palladium-catalyzed arylation reaction of urea with unactivated aryl bromides. It was found that both steric and electronic properties of the ligands have a pronounced effect on the yields and ratios of the products. Arylation of urea and phenylurea with unactivated aryl bromides in the presence of Pd2dba3·CHCl3/3,5-(CF3)2Xantphos and Cs2CO3 as base in dioxane at 100°C gave the corresponding N,N′-diarylureas in 62–98% yields.

Transition metal carbonylates in nucleophilic aromatic substitution: I. Influence of ionic association on the rates of reactions with perfluoroaromatic substrates

Abstract Quantitative yields of monosubstituted products were obtained from the reactions between CpFe(CO) 2 − (Cp = C 5 H 5 ), Re(CO) 5 − and C 6 F 6 , C 5 F 5 N; and CpW(CO) 3 − , Mn(CO) 5 − and C 5 F 5 N. The kinetics of the reactions of Re(CO) 5 − with C 6 F 6 , and of CpW(CO) 3 − and Mn(CO) 5 − with C 5 F 5 N were studied with respect to solvent, counterion, complexing agents and common ion effects. In all of the reactions studied, contact ion pairs were observed to be more reactive than solvent-separated ion pairs or free ions.

Halophilic reactions of pentafluorohalobenzenes with transition-metal carbonyl anions

Abstract In the present work we widen the scope of the halophilic mechanism of nucleophilic aromatic substitution, which we found earlier for the reaction of pentafluorochlorobenzene with [CpFe(CO) 2 ] − anion, to reactions of pentafluorohalobenzenes (Hal=Cl, Br, I) with various metal carbonyl anions [Re(CO) 5 ] − , [Mn(CO) 5 ] − and [CpFe(CO) 2 ] − . Nucleophilic aromatic substitution with the [CpFe(CO) 2 ] − anion yields C 6 F 5 Fe(CO) 2 Cp, while with [Re(CO) 5 ] − and [Mn(CO) 5 ] − anions the halo(acyl)metallates cis -[C 6 F 5 (CO)M(CO) 4 Hal]Na (M=Mn, Re) are obtained.

Air oxidation of in situ obtained carbanions in koh-dme-crownsystem

KOH(NaOH)-dimethoxyethane-18-crown-6-O2 system has been found to be efficient for generation and oxidation of carbanions, obtained from monoarylmethanes.

Nucleophilic vinylic substitution with transition metal carbonyl anions—a rare case of a halophilic reaction mechanism: Formation of halo(acyl)rhenate complexes and X-ray structure of cis-[CF2CF(CO)Re(CO)4Br]Na

Abstract Reactions of polyfluorinated alkenyl halides Z-(CF3)3CCFCFHal (Hal=Cl, I-Cl, Hal=Br, I-Br) and CF2CFBr (II-Br) with [CpFe(CO)2]K (FpK) and [Re(CO)5]Na proceed through the initial attack of metal carbonyl anion on halogen. Reaction with FpK gives minor amounts of σ-alkenyl complexes Z-RfCFCFFe(CO)2Cp (I-Fe, II-Fe) (3–30%), but primarily leads to dimer [CpFe(CO)2]2. Reaction with [Re(CO)5]Na produces anionic halo(acyl)rhenates cis-[Z-RfCFCF(CO)Re(CO)4Hal]Na (V-Cl, V-Br, VI) (70–90%) which were isolated, and halo(acyl)rhenate VI (Rf=F) was characterized by X-ray structure analysis. Halo(acyl)rhenates result from the attack of the intermediate carbanion [RfCFCF]− on the carbonyl ligand of Re(CO)5Hal. The involvement of [RfCFCF]− is demonstrated by their trapping with t-BuOH or CH-acid, which gives the protodehalogenated alkenes I-H and II-H, and suppresses the nucleophilic substitution reaction leading to I-Fe, II-Fe or V-Cl. Arguments against a radical/SET mechanism for the substitution reaction are also advanced.

Arylation of polyamines by perfluoroarenes

Abstract The conditions of selective mono- and diarylation of diamines, and di- and triarylation of triamines by perfluoroarenes are described. The introduction of four perfluoroaryl groups in cyclam and two groups in dioxocyclam has been carried out.

The reaction of the [CpFe(CO)(2)](-) anion with pentafluorochlorobenzene: Nucleophilic aromatic substitution by halogen-metal exchange

The mechanism of the reaction of [CpFe(CO)2]− with pentafluorochlorobenzene is investigated in detail. The reaction is shown to proceed exclusively through the [C6F5]− intermediate (below), which can be trapped with proton donors or with an excess of C6F5Cl.

N-aryl- and N-vinyldiaza-18-crown-6: Synthesis and complexing ability

The nucleophilic aromatic and vinyl substitution using diaza-18-crown-6 as nucleophile afforded a number of its N,N’-diaryl-[aryl = 2,4-(NO2)2C6H3, 4-C5F4N, 4-CF3C6F4] and N,N’-dialkenyl-substituted derivatives [alkenyl = PhC(O)CH=CH, MeOCOCH=CH, (EtO2C)2C=C(Ph), etc.]. Arylation of diaza-18-crown-6 with nonactivated aryl bromides, such as 4-Me2NC6H4Br, 4-MeOC6H4Br, C6H5Br, and 4-CF3C6H4Br, was effected under catalysis by palladium complexes. N,N’-Diaryldiaza-18-crowns-6 having electron-acceptor substituents in the aromatic rings turned out to be incapable of forming complexes with metal cations, while their analogs containing electron-donor para-methoxy and para-dimethylamino groups gave complexes with barium perchlorate.

Electrochemically induced aromatic nucleophilic substitution with [(η5-C5H5)Fe(CO)2]− and [(η5-C5H5Mo(CO)3]− anions

Abstract The reaction of low S N (Ar)-active and non-active aryl halides p -XC 6 H 4 Hal (X  CH 3 , H, Cl, COCH 3 , CN or NO 2 ; Hal  I or Br) with [(η 5 -C 5 H 5 )Fe(CO) 2 ] − and [(η 5 -C 5 H 5 )Mo(CO) 3 ] − is studied using a number of electrochemical methods (cyclic voltammetry, rotating-ring-disk-electrode technique and preparative-scale electrolysis). It is shown that the electrode catalysis enables one to carry out aromatic nucleophilic substitution which generally leads to σ-aryl derivatives of (η 5 -cyclopentadienyl) irondicarbonyl. Nevertheless, a detailed study of the mechanism of the reduction and oxidation of [(η 5 -C 5 H 5 )Fe(CO) 2 C 6 H 4 X- p ] at a Pt electrode reveals that the irreversibility of their reduction processes imposes certain restrictions on performing electrode-initiated aromatic nucleophilic substitution. This results in the occurrence of the “electrochemical activation window”, i.e. . limitation of the potential region where electrochemically induced aromatic nucleophilic substitution is possible. For the [(η 5 -C 5 H 5 )Mo(CO) 3 ] − anion, we failed to obtain its σ-aryl derivatives using electrochemical activation of aryl halides. The main product of the reaction is (η 5 -C 5 H 5 )Mo(CO) 3 Hal.