Bis(dimethylmetall)-N,N′,N″,N‴-tetramethyloxamidine des aluminiums,galliums und indiums; synthese,spektren und röntgenstrukturen

N,N′,N″,N?-Tetramethyloxamidine, (HNMe)₂C₂(NMe)₂, reacts with the trimethyl derivatives of Al, Ga and In, respectively, in a $\text{1}\text{2}$ molar ratio. Monomeric bis(dimethylmetal)oxamidines, [Me₂M]₂C₂(NMe)₄ with M = Al, Ga, In, and methane are formed. According to the vibrational spectra (IR and Raman) and the X-ray structure determinations of all three compounds these molecules consist of two fused five-membered rings, with an essentially planar structure. The results in the homologous series [Me₂M]₂C₂O_4?x(NMe)_x (x = 0, 2 and 4 and M = Ga) are compared.     

Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) as powerful reagents for benzylic bromination

N,N,N′,N′-Tetrabromobenzene-1,3-disulfonamide [TBBDA], poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS], and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) [PBPS] can be used for bromination of benzylic positions in solvent.     

Ruthenium(II) complexes of 2-(p.Toluidino)pyridine and rhodium(III) complexes of N,N′-di(2-pyridyl)-1,3-diamino-s-chlorobenzene

An attempted cyclometallation of 2-(p-toluidino)pyridine by dichlorotricarbonylruthenium(II) in refluxing 2-(methoxy)ethanol gave [RuCl(CO)₂(tp     

Enantiomerically enriched atropisomeric N,N′-diaryl ureas by oxidative kinetic resolution of their 2-sulfanyl derivatives

Atropisomeric N-methyl-N,N′-diaryl ureas may be obtained in enantiomerically enriched form by oxidative kinetic resolution of their sulfide derivatives. The atropisomeric sulfides may be obtained in up to 97:3 er and display high stability to racemisation (half-lives at 25 °C of up to 500 years). Unlike related fully alkylated ureas, the product sulfoxides exhibit relatively weak thermodynamic conformational selectivity.     

Crystallographic report: Di(p‐chlorobenzyl)tin bis(N‐methylpiperazinyldithiocarbamate)

The tin atom in (4‐Cl‐C₆H₄CH₂)₂Sn[S₂CN(CH₂CH₂)₂NCH₃]₂ is in a C₂S₄ skew‐trapezoidal bipyramidal geometry with the two carbon atoms being disposed over the weaker Sn? S bonds. Copyright © 2005 John Wiley & Sons, Ltd.     

The crystal and molecular structure of acetato(2-phenylazophenyl-C,N′)tellurium(II) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II)

The crystal and molecular structures of acetato(2-phenylazophenyl-C,N′)tellurium(II) (I) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II) (II) have been determined. The structure of the former consists of discrete molecules in which weak intramolecular Te?ctdot;O [2.953(4) Å] interactions occur. However, the structure of the latter compound shows a very weak intermolecular Te?ctdot;N [3.535(3) Å] interaction, which links the molecules into dimers. The coordination about tellurium can be considered as approximately trigonal bipyramidal with the carbon atom and the two lone pairs in the equatorial positions and either N and O(I) or N and S (II) in the axial positions.     

Crystallographic report: Di(o‐chlorobenzyl)tin(IV) bis(N‐methylpiperazinyldithiocarbamate)

The tin atom in {(2‐Cl‐C₆H₄CH₂)₂Sn[S₂CN(CH₂CH₂)₂NCH₃]₂}₂ is in a skew‐trapezoidal bipyramidal geometry defined by a C₂S₄ set with C? Sn? C 150.61(19)°. Centrosymmetric pairs associated via weak Sn·S to form a dimer. Copyright © 2005 John Wiley & Sons, Ltd.     

N-Isopropyl-N',N'-diphenyl-N-(silylmethyl)ureas: Synthesis and structure

New N-isopropyl-N',N'-diphenyl-N-(silylmethyl)ureas were obtained, and their structure was explored by ¹H, ¹³C, ²⁹Si NMR spectroscopy and X-ray analysis. These results have shown that N-isopropyl-N', N'-diphenyl-N-[(fluorosilyl)-methyl]ureas exist as (O–Si) chelates with intramolecular dative bond C=O→Si.     

Electric field dependence of charge carrier generation in alkane solutions of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD)

Studies of the electric field dependence or photocurrents from solutions of TMPD in non-polar solvents are interpreted using Onsager's theory of geminate charge recombination. For all solvents and photon energies, a simple exponential form of the radial distribution function for geminate pairs accounts for the observed field dependence.     

On the oxidative coupling of N,N-disubstituted 2-aminothiophenes—synthesis of N,N′-persubstituted 5,5′-diamino-2,2′-bithiophenes

The oxidative coupling of N,N-disubstituted 2-aminothiophenes performed by several heavy-metal free oxidizing agents gives rise to the formation of N,N′-persubstituted 5,5′-diamino-2,2′-bithiophenes which are of interest as hole-transport materials for optoelectronic applications.     

Novel synthesis of N,N′‐dialkyl cyclic ureas using sulfur‐assisted carbonylation and oxidation

The first example of cyclic urea synthesis from secondary amines by the use of sulfur‐assisted carbonylation and oxidation was established. By combined sulfur‐assisted carbonylation of secondary α,ω‐diamines under an ambient pressure of carbon monoxide at 20°C with oxidation by molecular oxygen (0.1 MPa, 20°C), a facile synthetic method for N,N′‐dialkyl cyclic ureas including 1,3‐dimethyl‐2‐imidazolidinone was developed. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:64–68, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20508     

Synthesis and characterization of soluble aromatic polyurea-amides from new N,N′--dimethyl-N,N′-bis(aminophenyl)ureas and aromatic dicarboxylic acid chlorides

Aromatic polyurea-amides having inherent viscosities of 0.36–0.67 dL/g were synthesized by the low temperature solution polycondensation of new N,N′-dimethyl-N,N′-bis(aminophenyl)ureas with various aromatic dicarboxylic acid chlorides. All the polymers were amorphous, and most of them were soluble in a variety of organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc), m-cresol, and pyridine. Some of the polymers could be cast from the DMAc solutions into transparent and flexible films having good tensile properties. The glass transition temperatures of the polyurea-amides obtained from the bis(4-aminophenyl)-substituted ureas were 244–272°C. The temperatures of 10% weight loss under nitrogen of the polymers were in the range of 430 and 480°C. © 1995 John Wiley & Sons, Inc.     

N,N-Bis(halomethyldimethylsilyl)acetamides and their reactions

N,N-Bis(halomethyldimethydimethylsilyl)acetamides, MeCON(SiMe₂CH₂X)₂, (X = Cl, Br) were prepared by transsilylation of N,O-bis(trimethylsilyl)acetamide with halomethyldimethylchlorosilane. With water and methanol, instead of the expected SiN cleavage, nucleophilic substitution of halogen took place and the products were 1-acetyl-2,2,6,6-tetramethyldisilamorpholine and N,N-bismethoxymethyldimethylsilyl)acetamide respectively. These compounds were shown by IR and ¹H NMR spectra to have the N,N-disilylacetamide structure. Thermodynamic, kinetic constants of hindered rotation around the CN bond in these compounds were determined from their temperature-variable ¹H NMR spectra. The main products of thermolysis of the silylamides are α,ω-dichloropolydimethylsiloxanes and polydimethylcyclosiloxanes.     

Enantioselective aza-Diels-Alder reaction of Brassard’s diene with aldimines catalyzed by chiral N,N′-dioxide-Yb(OTf)3 complex

The chiral N,N′-dioxide-Yb(OTf)₃ complex-catalyzed enantioselective aza-Diels-Alder reaction of Brassard’s diene with aldimines has been developed, giving the corresponding α,β-unsaturated δ-lactam derivatives in moderate yields with good enantioselectivities (up to 81% ee and up to 99% ee by single recrystallization) under mild conditions. Isolation of the reaction intermediate indicates that this asymmetric aza-Diels-Alder reaction proceeds through a stepwise Mannich-type pathway.     

New seven-coordinate thiourea and N,N,N′,N′-tetramethylthiourea complexes of molybdenum(II) and tungsten(II)

The compounds [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with one equivalent of thiourea (tu) in MeOH or N,N,N′,N′-tetramethylthiourea (tmtu) in CH₂Cl₂ at room temperature to initially afford the monoacetonitrile compounds [MI₂(CO)₃(NCMe)L] (L = tu or tmtu) which rapidly transform to the isolated iodide bridged dimers, [M(μ-I)I(CO)₃L]₂ with loss of acetonitrile. Reaction of [WI₂(CO)₃(NCMe)₂] with two equivalents of tu or tmtu gave the expected mononuclear seven-coordinate compounds [WI₂(CO)₃L₂]. However, reaction of [MoI₂(CO)₃(NCMe)₂] with two equivalents of tu or tmtu rapidly affords the iodide-bridged dimers [Mo(μ-I)I(CO)₂L₂]₂ with loss of carbon monoxide from [MoI₂(CO)₃L₂]. The low temperature (−70°C) ¹³C NMR spectrum of [Mo(μ-I)I(CO)₂ {SC(NMe₂)₂}₂]₂ suggests the complex is based on two capped octahedra with a carbonyl ligand capping each octahedral face.     

Tetramethylammonium trifluoromethyltellurate(0), [NMe4]TeCF3, synthesis, characterisation and properties

[NMe₄]TeCF₃ is obtained in 60% yield from Me₃SiCF₃, elemental tellurium and [NMe₄]F in glyme as a pale yellow solid decomposing at 185 °C. Cation exchange with [PNP]Br ([PNP] = bis(triphenylphosphoranylidene)ammonium) and [(dibenzo-18-crown-6)K]Br occurs spontaneously. These low co-ordinating cations increase significantly the nucleophilicity of the anion.     

Diversity-oriented synthesis of N,N-dimethylamino-substituted azoles employing TBTU

A convenient, diversity-oriented approach for the transformation of readily available amidoximes, o-hydroxyarylamines, acyl hydrazines, carboximidohydrazides and thiohydrazides into their respective N,N-dimethylamino-substituted azoles is described. The method is particularly suitable for array chemistry application as it employs a stable, solid reagent TBTU.     

Chiral Non-racemic Bis(vicinal 1,2-Diamines): 4,5-Diamino-N-(3,4-diaminobutyl)pentanamide Tetrahydrochloride, N,N′-Bis[3,4-bis (t-butoxycarbonylamino)butyl]urea and N,N′Bis

The reaction of (R) or (S)-N⁴,N⁵-bis(t-butoxycarbonyl)-4,5-diaminopentanoic acid (6) with (R) or (S)-N³,N⁴-bis(t-butoxycarbonyl)-3,4-diaminobutylisocyanate (8) catalyzed by 4-dimethylamino pyridine (DMAP), leads to the synthesis of (R,R), (S,S), (R,S) and (S,R) isomeric amides (11 a — d) The addition of adipic acid monomethyl ester to (R) or (S) isocyanate, followed by saponification, acidification and subsequent reaction with the second molecule of (R) or (S) isocyanate allows isolation of the (R,R), (S.S) and the meso isomers of N,N′-bis[3,4-bis(t-butoxycarbonylamino) butyl]hexanediamide (17) Removal of protecting groups with HCl/EtOH affords chiral non-racemic molecules having two free vicinal diamine units.     

Preparation and crystal structure of dioxotetrachloro-(N,N′-ethylenebis(salicylideneiminato)bis(triphenylphosphine)-dirhenium(V) dichloromethane solvate

The complex ReOCl₃(PPh₃)₂ reacts with bis(trimethylsilyl)-N,N′-ethylenebis(salicylideneiminato) to give a complex in which the “salen” ligand bridges two rhenium atoms, viz. dioxotetrachloro(N,N′-ethylenebis(salicylideneiminato)bis(triphenylphosphine)dirhenium(V). Its crystal and molecular structure have been determined by a single crystal X-ray diffraction analysis. The crystals are monoclinic space group P2₁/c with four molecules in a cell of dimensions a 18.609(4), b 16.286(4), c 18.600(4)Å and β 105.00(2)°. Least squares refinement of 5867 observed reflections measured on a diffractometer reached R = 0.045. The “salen” ligand bridges two rhenium atoms which present a distorted octahedral coordination. The two halves of the molecule are approximately related by a non-crystallographic two fold axis perpendicular to the CC bond of the ethylenic group.