Copper(II) triflate promoted cycloaddition of α-alkyl or aryl substituted N-tosylaziridines with nitriles: a highly efficient synthesis of substituted imidazolines

Cu(OTf)₂ or Zn(OTf)₂ mediated [3+2] cycloaddition reactions of various α-alkyl or aryl substituted N-tosylaziridines with nitriles is described for the syntheses of substituted imidazolines. A mechanism for the cycloaddition is proposed to rationalize the formation of a nonracemic imidazoline from optically pure aziridine.     

Nickel(II) and zinc(II) complexes of N-substituted di(2-picolyl)amine derivatives: Synthetic and structural studies

The interaction of di(2-picolyl)amine (1) and its secondary N-substituted derivatives, N-(4-pyridylmethyl)-di(2-picolyl)amine (2), N-(4-carboxymethyl-benzyl)-di(2-picolyl)amine (3), N-(4-carboxybenzyl)-di(2-picolyl)amine (4), N-(1-naphthylmethyl)-di(2-picolyl)amine (5), N-(9-anthracenylmethyl)-di(2-picolyl)amine (6), 1,4-bis[di(2-picolyl)aminomethyl]benzene (7), 1,3-bis[di(2-picolyl)aminomethyl]benzene (8) and 2,4,6-tris[di(2-picolyl)amino]triazine (9) with Ni(II) and/or Zn(II) nitrate has resulted in the isolation of [Ni(1)(NO₃)₂], [Ni(2)(NO₃)₂], [Ni(3)(NO₃)₂], [Ni(4)(NO₃)₂]·CH₃CN, [Ni(5)(NO₃)₂], [Ni(6)(NO₃)₂], [Ni₂(7)(NO₃)₄], [Ni₂(8)(NO₃)₄], [Ni₃(9)(NO₃)₆]·3H₂O, [Zn(3)(NO₃)₂]·0.5CH₃OH, [Zn(5)(NO₃)₂], [Zn(6)(NO₃)₂], [Zn(8)(NO₃)₂] and [Zn₂(9)(NO₃)₄]·0.5H₂O. X-ray structures of [Ni(4)(NO₃)₂]·CH₃CN, [Ni(6)(NO₃)₂] and [Zn(5)(NO₃)₂] have been obtained. Both nickel complexes exhibit related distorted octahedral coordination geometries in which 4 and 6 are tridentate and bound meridionally via their respective N₃-donor sets, with the remaining coordination positions in each complex occupied by a monodentate and a bidentate nitrato ligand. For [Ni(4)(NO₃)₂]·CH₃CN, intramolecular hydrogen bond interactions are present between the carboxylic OH group on one complex and the oxygen of a monodentate nitrate on an adjacent complex such that the complexes are linked in chains which are in turn crosslinked by intermolecular offset π-π stacking between pyridyl rings in adjacent chains. In the case of [Ni(6)(NO₃)₂], two weak CH?O hydrogen bonds are present between the axial methylene hydrogen atoms on one complex and the oxygen of a monodentate nitrate ligand on a second unit such that four hydrogen bonds link pairs of complexes; in addition, an extensive series of π-π stacking interactions link individual complex units throughout the crystal lattice. The X-ray structure of [Zn(5)(NO₃)₂] shows that the metal centre once again has a distorted six-coordinated geometry, with the N₃-donor set of N-(1-naphthylmethyl)-di(2-picolyl)amine (5) coordinating in a meridional fashion and the remaining coordination positions occupied by a monodentate and a bidentate nitrato ligand. The crystal lattice is stabilized by weak intermolecular interactions between oxygens on the bound nitrato ligands and aromatic CH hydrogens on adjacent complexes; intermolecular π-π stacking between aromatic rings is also present.     

From alkenylphosphane aminoallenylidene ruthenium(II) complexes to highly unsaturated ruthenaphosphabicycloheptene complexes

The alkenylaminoallenylidene complex [Ru(η⁵-C₉H₇){CCC(NEt₂)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (2) has been prepared by the reaction of the allenylidene [Ru(η⁵-C₉H₇)(CCCPh₂){κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (1) with the ynamine MeCCNEt₂. The reaction proceeds regio- and stereoselectively, and the insertion of the ynamine takes place exclusively at the C_βC_γ bond of the unsaturated chain. The secondary allenylidene [Ru(η⁵-C₉H₇){CCC(H)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (3) is obtained, in a one-pot synthesis, from the reaction of aminoallenylidene 2 with LiBHEt₃ and subsequent treatment with silica. Moreover, the addition of an excess of NaBH₄ to a solution of the complex 2 in THF at room temperature gives exclusively the alkynyl complex [Ru(η⁵-C₉H₇){CCCH₂[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)] (5). The heating of a solution of allenylidene derivative 3 in THF at reflux gives regio- and diastereoselectively the cyclobutylidene complex [Ru(η⁵-C₉H₇) (PPh₃)][PF₆](4) through an intramolecular cycloaddition of the CC allyl and the C_αC_β bonds in the allenylidene complex 3. The structure of complex 4 has been determined by single crystal X-ray diffraction analysis.     

Synthesis and structural characterization of novel zinc(II) and cadmium(II) complexes with pyridine-phosphine chalcogenide ligands

New pyridine-phosphine chalcogenide ligands, tris[2-(2-pyridyl)ethyl]phosphine sulfide 1a and tris[2-(2-pyridyl)ethyl]phosphine selenide 1b, react with zinc(II) and cadmium(II) chlorides in EtOH at room temperature to afford complexes of compositions 2ZnCl₂·2L (2, L = 1a) and 3CdCl₂·2L (3a,b, L = 1a,b) in high yields. The solid-state structure of complexes 2, 3 has been proved by X-ray analysis data. Complex 2 is a centrosymmetric dimer, where two atoms of zinc are bonded by two bridging pyridine-phosphine sulfide ligands through N atoms. Complexes 3a,b exist as polymeric chains with each bridging ligand acting as a chelate N,S- or N,Se-donor to one cadmium(II) center and as a pyridine N-donor to the next cadmium(II) center.     

Synthesis of 4-(2-hydroxy-1-methyl-5-oxo-1H-imidazol-4(5H)-ylidene)-5-oxo-1-aryl-4,5-dihydro-1H-pyrrole-3-carboxylates, a new triazafulvalene system

(2E,3Z)-2-(1-Methyl-2,5-dioxoimidazolidin-4-ylidene)-3-[(arylamino- or heteroarylamino)methylene]succinate 5 obtained by [2+2] cycloaddition of (5Z)-5-[(dimethylamino)methylene]-3-methylimidazolidine-2,4-dione (1) and dimethyl acetylenedicarboxylate (2) followed by substitution of the dimethylamino group with aromatic or heteroaromatic amines, afforded by heating in ethanol in the presence of potassium hydroxide, potassium salts 6. Acidification of 6 with hydrochloric acid afforded mixtures of (E)- and (Z)-isomers of methyl 4-(2-hydroxy-1-methyl-5-oxo-1H-imidazol-4(5H)-ylidene)-5-oxo-1-phenyl-4,5-dihydro-1H-pyrrole-3-carboxylates. On the other hand, alkylation of compounds 6 with methyl iodide or benzyl bromide produced the corresponding methyl (E)-4-(2-methoxy- or 2-benzyloxy-1-methyl-5-oxo-1H-imidazol-4(5H)-ylidene)-5-oxo-1-phenyl-4,5-dihydro-1H-pyrrole-3-carboxylates 9, derivatives of a new triazafulvalene system.     

Reactions of N-vinylic phosphazenes with azodicarboxylic and acetylenic esters

N-Vinylic phosphazenes react as enamines (1,4-addition) with azodicarboxylic esters, whereas different behavior is observed when these phosphazenes react with dimethyl acetylenedicarboxylate (3,4-addition). A [2+2] cycloaddition reaction of the vinyl moiety of vinylic phosphazenes with the acetylenic triple bond of the acetylenic esters followed by a ring opening leads to the formation of functionalized conjugated phosphazenes.     

Nickel(II) and zinc(II) complexes with N-(5,6-dihydro-4H-1,3-thiazin-2-yl)-2-aminobenzimidazole (BzTz): Synthesis,spectral and structural characterization

The reaction of nickel and zinc chlorides and nitrates with the ligand N-(5,6-dihydro-4H-1,3-thiazin-2-yl)-2-aminobenzimidazole (BzTz) leads to the formation of the new complexes: [NiCl₂(BzTz)₂] (1), [Ni(NO₃)(BzTz)₂(H₂O)₃](NO₃) (2), [ZnCl₂(BzTz)₂] (3) and [Zn(NO₃)₂(BzTz)₂] (4). They have been characterized by spectroscopic methods (electronic, infrared and NMR) and magnetic susceptibility measurements. Additionally, the crystal structures of the complexes 1 and 3 have been determined by X-ray single-crystal diffraction. The ligand exhibits the N-benzimidazole coordination mode on interacting with the metal centers. The X-ray structure of the complexes 1 and 3 reveals a distorted tetrahedral coordination geometry around the metal center, with the metallic atoms coordinated to two chlorine atoms and two benzimidazole nitrogen atoms. These two complexes are isostructural, crystallizing in the monoclinic system and Cc space group. In complex 2 the geometry around the nickel atom could be described as a distorted octahedron whereas in case of complex 4 the zinc atom is in a distorted tetrahedral environment.     

Chiral N-phosphino sulfinamide ligands in rhodium(I)-catalyzed [2+2+2] cycloaddition reactions

The combination of cationic rhodium(I) complexes with N-phosphino tert-butylsulfinamides (PNSO) ligands is efficient for catalytic intra- and intermolecular [2+2+2] cycloaddition reactions. PNSO ligands are a new class of chiral bidentate ligands, which have the characteristic of combining the easily accessible sulfur chirality with the coordinating capacity of phosphorous. Cycloaddition of open-chained and macrocyclic E-enediynes with these chiral complexes have proved to be highly efficient in terms of yields, giving moderate enantiomeric excesses of the corresponding cyclohexadiene derivatives. In addition Rh(I)/PNSO complexes catalyzed the intermolecular cycloaddition of diynes with monoalkynes in mild reaction conditions and short reaction times.     

[4+1] Cycloaddition of N-acylimine derivatives with isocyanides: efficient synthesis of 5-aminooxazoles and 5-aminothiazoles

[4+1] Cycloaddition reaction between isocyanides and N-acylimine derivatives generated from N-acyl N,O-acetals acting as isocyanophiles has been developed. These reactions proceeded smoothly and cleanly to afford the corresponding 5-aminooxazoles in high yields. This reaction was extended to the syntheses of 5-aminothiazoles by using N-thioacyl N,O-acetals. A wide range of N-acyl N,O-acetals, N-thioacyl N,O-acetals, and isocyanides were found to be applicable to this reaction.     

The Lewis acid-catalyzed [3+1+1] cycloaddition of azomethine ylides with isocyanides

A Lewis acid-catalyzed [3+1+1] cycloaddition reaction between aliphatic isocyanides and azomethine ylides generated in situ from aziridines, leading to pyrrolidine derivatives, has been developed. This reaction proceeds smoothly under mild conditions and can also be modified by employing aromatic isocyanides to generate four-membered heterocycles, azetidines, through a [3+1] cycloaddition reaction.     

Some neutral three-coordinate complexes of mercury(II) halides and pseudohalides with N-methylnicotinamide

Coordination compounds of mercury(II) chloride, bromide, cyanide and thiocyanate with N-methylnicotinamide, a potentially bidentate ligand, have been prepared. The complexesisolated have 1∶1 (metal:ligand)stoichiometry. Molecular weight measurements in molten camphor indicate that the mercury (II) chloride and bromide complexes are monomeric. Based on conductance values, molecular weight determinations and infrared spectral data, it is inferred that in the solid state in all these complexes the metal ion has a coordination number three and is bonded to the N-methylnicotinamide via its pyridine ring nitrogen, and is terminally bonded to the halogen/pseudohalogens.     

A zinc(II) complex with tris(2-( N -methyl)benzimidazlylmethyl)amine and salicylate: synthesis,crystal structure,and DNA-binding

A five-coordinate zinc complex with tris(2-(N-methyl)benzimidazylmethyl)amine (Mentb) and salicylate, with composition [Zn(Mentb)(salicylate)](NO₃), was synthesized and characterized by elemental analysis, IR and UV-Vis spectral measurements. The crystal structure of the zinc complex shows that Zn(II) is bonded to tris(2-(N-methyl)benzimidazylmethyl)amine (Mentb) and a salicylate through four nitrogens and one oxygen, and the coordination geometry is best described as distorted trigonal-bipyramid. The DNA-binding of the Zn(II) complex and Mentb were investigated by spectrophotometric methods and viscosity measurements, and the results suggest that the Zn(II) complex binds to DNA via intercalation; the binding affinity of the Zn(II) complex to DNA is greater than Mentb. Additionally, Zn(II) complex exhibited potential to scavenge hydroxyl radical in vitro.     

An efficient tris-(2-aminoethyl)amine-CuI-catalyzed thioetherification of thiols with aryl halides

A robust method has been developed to couple a wide variety of thiols and aryl halides. The C-S bond forming reaction makes use of catalytic copper(I) iodide and the ligand tris-(2-aminoethyl)amine. These conditions tolerate a wide degree of functionality on both aryl halide and thiol reactants and have resulted in numerous examples being synthesized. Commercial availability of the ready to use, inexpensive ligand, tris-(2-aminoethyl)amine and air-stable CuI make the method well suited to generate a diverse array of diaryl thioethers.     

An efficient synthetic route to substituted tetrahydropyrimidines by Cu(OTf)2-mediated nucleophilic ring-opening followed by the [4+2] cycloaddition of N-tosylazetidines with nitriles

A highly efficient strategy for Cu(OTf)₂-mediated S_N2 type nucleophilic ring-opening followed by the [4+2] cycloaddition reactions of a number of 2-aryl-N-tosylazetidines with nitriles to afford a variety of substituted tetrahydropyrimidines in excellent yields is reported. The resulting tetrahydropyrimidines could easily be transformed into synthetically important 1,3-diamines by acid-catalyzed hydrolysis. The strategy has been extended to the synthesis of enantiomerically pure tetrahydropyrimidines from enantiopure disubstituted azetidines. The reaction proceeds through an S_N2 type mechanism as proposed by us earlier.     

Photochemical Experiments with 2,3-Bis(Tert-Butylsulfonyl)Bicyclo[2.2.2]Octa-2,5-Diene and Related Systems

The irradiation of 2,3-bis(tert-butylsulfonyl)norbornadiene (5) and 2-(tert-butylsulfonyl)norbornadiene (6) yielded the expected quadricyclane derivatives as stable molecules. The irradiation of 2,3-bis(tert-butylsulfonyl)bicyclo[2.2.2]octa-2,5-diene(7) 2,3-bis(tert-butylsulfonyl)-exo-7,8-epoxybicyclo[2.2.2]-octa-2,5-diene (8) and 8,9-bis(tert-butylsulfonyl)-4-anti-phenyl-3,5-dioxa-exo-tricyclo[5.2.2.0^2,6] undeca-8,10-diene 9a and its syn-isomer 9b yielded the corresponding tetracyclic and pentacyclic systems, respectively. The photoproducts of 8 and 9 reverted to the starting products slowly at room temperature. The half-life of the photoproduct of 7 was determined to be 34 min at 50 °C. Compound 9a reacted with n-BuLi to yield the unexpected desulfonylation product 27a.     

Syntheses and crystal structures of nickel(II), copper(II), and zinc(II) complexes with a biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand

The reactions of nickel(II), copper(II), and zinc(II) acetate salts with a potentially tetradentate biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand yielded three complexes with different coordination geometries. X-ray crystal structural analysis reveals that in the nickel(II) complex each nickel is five-coordinate, distorted trigonal bipyramid. In the copper(II) complex, each copper is four-coordinate, between square planar and tetrahedral. In the zinc(II) complex, each zinc is four-coordinate with a distorted tetrahedral geometry and the molar ratio of the zinc and ligand is 1 : 2.     

A study of complex equilibria of phenylglycine with nickel(II), copper(II) and zinc(II) in water and in water - methanol solution

The complex equilibria of the systems phenylglycine — nickel(II), copper(II) and zinc(II) in water and in water — methanol solution have been studied by computer analysis of potentiometric data. The mode of coordination has been established by¹³C-NMR and IR studies.

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Gleichgewichtsuntersuchungen der Komplexbildung von Phenylglycin mit Nickel(II), Kupfer(II) und Zink(II) in Wasser und Wasser - Methanol-Lösung

Zusammenfassung Anhand einer Computer-Analyse von potentiometrischen Daten wurden die Bildungsgleichgewichte in den Systemen Phenylglycin — Nickel(II), Kupfer(II) und Zink(II) untersucht. Der Koordinationstyp wurde mittels¹³C-NMR und IR festgestellt. Die Lösungsmittel waren Wasser und Wasser — Methanol.

     

Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide

Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time.     

纳米银粒子对[Ru(bpy)_3]~(2+)光谱学性质的影响及电解质效应

研究了[Ru(bpy)3]2+溶液中引入纳米银粒子的光谱学性质变化规律以及[Ru(bpy)3]2+与纳米银粒子所构成的溶液体系([Ru(bpy)3]2+-Ag)的电解质效应.研究结果表明,[Ru(bpy)3]2+吸附在纳米银粒子表面使纳米银粒子相互桥连形成规则的类链状网络聚集体.纳米银粒子造成[Ru(bpy)3]2+溶液荧光猝灭,且大尺寸的纳米银粒子引起的荧光猝灭程度较大.在[Ru(bpy)3]2+-Ag体系中引入电解质造成纳米银粒子不同程度的聚集和生长.电解质对纳米银聚集影响为:CaCl2MgCl2Ca(NO3)2KClKNO3.随着[Ru(bpy)3]2+-Ag体系中引入电解质含量的增加,溶液的荧光强度先降低而后又逐渐增强,直至达到定值,表明一定量的电解质可产生荧光猝灭释放效应.电解质对荧光强度影响顺序为:Ca(NO3)2CaCl2MgCl2KClKNO3.采用透射电子显微镜、紫外-可见吸收分光光度计和荧光分光光度计等手段从分子间相互作用和能量传输等方面初步探讨了纳米银粒子对表面吸附[Ru(bpy)3]2+溶液光谱学性质的影响机制以及电解质效应.     

N-Iodosaccharin (NISac): a new reusable catalyst for formal [2+4] cycloaddition of imines and enones

The first example of N-iodosaccharin (NISac)-catalyzed step, pot and atom economic synthesis of 1,3-oxazines via formal [2+4] cycloaddition of imines and enones has been reported. No by-product formation, operational simplicity, ambient temperature and high yields (85-95%) are the salient features of the present synthetic protocol. After isolation of the product, the catalyst NISac can be easily recovered and reused without any loss of efficiency.