LIGAND COUPLING AND PSEUDOROTATION IN THE REACTION OF ALKYL 2-PYRIDYL SULFOXIDE WITH GRIGNARD REAGENTS

Abstract

In the reaction of benzyl 2-pyridyl sulfoxide (1) with C₆H₅CH₂MgCl, the incoming Grignard reagent tends to couple preferentially with 2-pyridyl group at lower temperatures, whereas, at higher temperatures, coupling between benzyl and 2-pyridyl groups with 1 tends to increase due presumably to the relatively more facile pseudorotation² at higher temperatures.     

LIGAND EXCHANGE AND LIGAND COUPLING VIA THE σ-SULFURANE INTERMEDIATE IN THE REACTION OF ALKYL 2-PYRIDYL SULFOXIDE WITH GRIGNARD REAGENTS: CONVENIENT PREPARATION OF 2,2′-BIPYRIDINES

Abstract

The reaction between methyl 2-pyridyl sulfoxide (1) with Grignard reagents afforded 2,2′-bipyridine (2) in moderate yield. The reaction is considered to involve initial ligand exchange to generate 2-pyridylmagnesium halide which in the subsequent step attacks the original sulfoxide to form the σ-sulfurane that undergoes ligand coupling to afford 2. The reaction of t-butyl 2-pyridyl sulfoxide (3) with C₆H₅MgBr, however, gave only 2-phenylpyridine (4). This may be due to steric hindrance to the initial ligand exchange. Formation of 2 is a convenient process for preparation of 2,2′-bipyridines bearing various substituents.     

AN UNUSUAL RUTHENIUM(II) COMPLEX OF 2-(2-PYRIDYL)BENZOTHIAZOLE

Abstract

The ligand 2-(2-pyridyl)benzothiazole (L) can act both as an N-N and an N-S chelating donor. The latter coordination mode is expected to be preferred when it is involved in coordination to Ru(II) which is a soft acceptor centre However, in the title compound, chlorobis(acetonitrile)triphenylphosphino-2-(2-pyridyl)benzothiazole-N,N-ruthenium(II) chlride, [Ru(L)(PPh₃(CH₃CN)₂Cl]Cl, the ligand acts in N,N-bidentate manner and the Ru(II) ion is found to be present in an N₄PCl coordination environment. PPh₃ and Cl are trans to each other and the two CH₃CN ligands occupy cis positions facing the NN donor atoms of ligand L.     

Spectroscopic,thermal and structural studies of a new mercury(II) one-dimensional coordination polymer, [Hg(3-bpo)2(SCN)2], 3-bpo = 2,5- bis (3-pyridyl)-1,3,4-oxadiazole

A new mercury(II)-organic polymeric complex generated from 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) as an angular dipyridyl derivative ligand, [Hg(3-bpo)₂(SCN)₂], was prepared from reactions of ligand 3-bpo with mercury(II) thiocyanate. The compound was characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR-spectroscopy and structurally determined by X-ray single crystal diffraction. The thermal stability of [Hg(3-bpo)₂(SCN)₂] was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

Electrogenerated Base-Promoted Synthesis of Dithiocarbamate Acid Esters and 3-(N-Substituted-amino)-2-cyanodithiocrotonates from Primary or Secondary Amines and Carbon Disulfide

Electrogenerated cyanomethyl anion promotes the reaction between primary or secondary amines, carbon disulfide, and alkyl or benzyl halide. Secondary amines are converted to alkyl or benzyl dithiocarbamates, whereas primary amines give N-substituted alkyl or benzyl 3-amino-2-cyanodithiocrotonates. The mechanisms are discussed.     

Asymmetric oxidation of sulfides catalyzed by (R)-6,6'-dibromo-BINOL derived titanium complex

Abstract

An efficient asymmetric oxidation of sulfides was achieved using (R)-6,6'-dibromo-BINOL as chiral ligand in combination with Ti(OⁱPr)₄ using 70% aqueous tertiary butyl hydroperoxide as oxidant. The resulting sulfoxides had high enantiopurities and good yields. A range of aryl alkyl and aryl benzyl sulfides were oxidized to the corresponding sulfoxides with 78–95% ee in 72–80% yields.     

A 2-D nickel coordination polymer with an unsymmetric ligand, 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione

A new nickel coordination polymer was obtained from an unsymmetric building block 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione (HL6) and Ni(NO₃)₂ · 6H₂O-afforded [Ni(L6)₂(H₂O)₂] _n (1) with a (4,4) network. Complex 1 exhibits moderate antimicrobial activity against Bacillus subtilis ATCC 6633 and Candida albicans ATCC 90028. Thermogravimetric data and magnetic moments for 1 have been investigated.     

Triphenylphosphine-supported synthesis of two-dimensional silver(I) complex with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

The reaction of dicarboxylate ligand, (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H₂tdza) with silver(I) acetate and triphenylphosphine (PPh₃) facilitate the formation of complex [Ag₂(tdza)(PPh₃)₂]_n (1). The complex was characterized by elemental analysis, FT-IR spectroscopy, ¹H-NMR, ¹³C-NMR and ³¹P-NMR spectroscopy, and single crystal X-ray diffraction. Structural analysis revealed that complex 1 has a 2D topologically promising architecture as a result from the formation of 26-membered cyclic ring. The tdza2^? ligand in 1 displays unprecedented µ₄-bridging mode which is also the first example for this ligand. The interdigitating arrangement and π-π stacking between 2D arrays stabilized the formation of complex 1.     

Synthesis,structures, and luminescent properties of two cadmium polymers of 4-carboxyl phenoxyacetate and 2-(2-pyridyl)benzimidazole

Two-dimensional complexes of [Cd(cpoa)(o-pbim)] _n (1) and {[Cd₃(cpoa)₃(o-pbim)₂] · 2H₂O} _n (2) (cpoa²⁻ = 4-carboxyphenoxy acetate, o-pbim = 2-(2-pyridyl)benzimidazole) are synthesized under hydrothermal condition. Single crystal X-ray diffraction analysis shows that complex 1 contains a mono-nuclear unit, whereas complex 2 contains a trinuclear unit. The structural difference of 1 and 2 can be attributed to the various coordination modes of asymmetrically semi-flexible cpoa²⁻ ligand. The luminescent properties of these two compounds are also investigated.     

1H-3-(3-吡啶基)-5-(3'-吡啶基)-1,2,4-三唑的钴(Ⅱ)配合物的合成、晶体结构、热稳定性及配体的DFT计算

合成了一个多功能的配体1H-3-(3-吡啶)-5-(3'-吡啶)-1,2,4-三唑(3,3'-Hbpt,1)并得到了配体的晶体结构,运用DFT理论计算了配体的最优构型、优势构象和电荷分布。在此基础上,水热合成了一个配位化合物:[Co(3,3'-Hbpt)₂(H₂O)₄]·(ad)·6H₂O(2)(ad=己二酸),结构分析表明配合物2是零维单核化合物,它的三维超分子结构是由分子间氢键连接而成,其中包含着由游离的己二酸分子填充的矩形孔道。值得注意的是,配体在配合物中的几何结构和构象与理论计算的结果一致。另外,利用热重分析研究了配合物2的热稳定性。     

1H-3-(3-吡啶基)-5-(3'-吡啶基)-1,2,4-三唑的钴(Ⅱ)配合物的合成、晶体结构、热稳定性及配体的DFT计算

合成了一个多功能的配体1H-3-(3-吡啶)-5-(3'-吡啶)-1,2,4-三唑(3,3'-Hbpt, 1)并得到了配体的晶体结构。运用DFT理论计算了配体的最优构型、优势构象和电荷分布。在此基础上,水热合成了一个配位化合物:[Co(3,3'-Hbpt)₂(H₂O)₄]·(ad)·6H₂O(2)(ad=己二酸), 结构分析表明配合物2是零维单核化合物,它的三维超分子结构是由分子间氢键连接而成,其中包含着由游离的己二酸分子填充的矩形孔道。值得注意的是,配体在配合物中的几何结构和构象与理论计算的结果一致。另外,利用热重分析研究了配合物2的热稳定性。     

Investigation of the Addition of Benzenethiol to p-Chlorophenylphenylacetylene

The addition of benzenethiol to p-chlorophenylphenylacetylene results in the formation of a mixture of two pairs of diastereomeric (E)- and (Z)-1-p-chlorophenyl-2-phenyl-1-phenylthioethylenes (1 and 2) and (E)- and (Z)-1-p-chlorophenyl-2-phenyl-2-phenylthioethylenes (3 and 4). The configurations of these compounds have been established by ¹ H NMR studies, by their preparation from benzyl p-chlorophenyl ketone and p-chloro-benzylphenyl ketone, and by the oxidation of the thioethylenes 1, 2, 3, and 4 to the corresponding sulphonylethylenes 5, 6, 7, and 8, respectively.     

Boron chelate complexes with some enaminones and diketones containing the pyridine fragment and their mutual transformations in solutions

The interaction of Ph₂BOBu with 4-amino-4-(2-pyridyl)-3-buten-2-one, 3-amino-1-(2-pyridyl)-2-buten-I-one, and 1-(2-pyridyl)butan-1,3-dione was investigated. The 5- or 6-membered chelates withN,O- orN,N-coordination of boron are formed depending on the pyridine-containing ligand structure. These complexes are capable of mutual transformation in solutions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 710–714, March, 1996.     

2-(2-氨基-3-吡啶基)-苯并咪唑的合成、晶体结构和荧光特性研究

在合成2-(2-氨基-3-吡啶基)-苯并咪唑的基础上,利用NMR(1H、13C、COSY、HSQC和HMBC)、MS、IR和UV进行了详细表征;通过X-ray单晶衍射仪测定了该化合物的晶体结构,实验结果表明该晶体属于三方晶系(空间群R3,a=1.833 7(3)nm,b=1.833 7(2)nm,c=1.777 7(4)nm,V=5.176 4(15)nm3,Z=18),很好地支持了波谱表征的结果。同时,结合密度泛函计算,研究了2-(2-氨基-3-吡啶基)-苯并咪唑的荧光光谱。结果表明,化合物的双荧光不是由同一种异构体发射的,而是来源于不同异构体:长波区500~600 nm的荧光由K构型发射,短波区350~450 nm的发射由异构体E1和E2共同产生,理论预测的光谱与实验一致。     

Hydrothermal synthesis,crystal structure and characterization of a new 1-D supramolecular ladder based on a binuclear CdII complex [Cd2L4(3,5-DNBA)2](H2O) with L as a bridging ligand (L=3-(2-pyridyl)pyrazole; 3,5-DNBA=3,5-dinitrobenzoate)

A new 1-D cadmium(II) mixed ligand dimer supramolecular ladder [Cd₂ L ₄(3,5-DNBA)₂]H₂O (1), (L?=?3-(2-pyridyl)pyrazole and 3,5-DNBA?=?3,5-dinitrobenzoate) was synthesized by hydrothermal methods. X-ray structural analysis of complex 1 revealed that two cadmium(II) cores are bridged by two deprotonated pyrazole groups of L, leading to dinuclear cadmium(II) [Cd₂ L ₄(3,5-DNBA)₂]. The dimers are joined by hydrogen-bonding interactions between two different cadmium(II) dimers to form a one-dimensional ladder-like framework and stabilized by weak π–π interactions. Moreover, the fluorescence spectrum of compound 1 exhibits blue fluorescent emission in the solid state at room temperature.     

3,3,3-Trifluoro-<Emphasis Type="Italic">N</Emphasis>′-(3-trifluoromethylphenyl)-1,2-propanediamine and its <Emphasis Type="Italic">N</Emphasis>-mono-and <Emphasis Type="Italic">N,N</Emphasis>-dicarboxyethyl derivatives: synthesis,protolytic and complexation properties

3,3,3-Trifluoro-N′-(3-trifluoromethylphenyl)-1,2-propanediamine (5) was synthesized by the reaction of 2-diazo-1,1,1-trifluoro-3-nitropropane or 3,3,3-trifluoro-1-nitropropene with 3-aminobenzotrifluoride followed by the reduction of the nitro group. The Michael 1,4-addition of diamine 5 to acrylic acid occurs only at the N(1) atom and affords N-mono-or N,N-dicarboxyethyl derivatives 6 and 7, depending on the reactant ratio. Protolytic equilibria 5–7 in aqueous solutions were studied by pH-potentiometry and UV spectroscopy. Only the aliphatic amino group can be protonated in an aqueous solution, while the aromatic amino group remains unprotonated even in 12 M HCl. The stability constants of transition metal (Cu²⁺, Ni²⁺, Zn²⁺) complexes with ligands 5–7 were determined by pH-potentiometric titration. The stability of the complexes and selectivity of the ligands toward Cu²⁺ ions increase with an increase in the number of N-carboxyethyl groups. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2465–2469, November, 2005.     

Syntheses and X-ray structural studies of the novel complexes [Ni(en)2(3-pyt)2] and [Cu(en)2](3-pyt)2 based on 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione

Two novel mononuclear mixed-ligand complexes [Ni(en)₂(3-pyt)₂] (1) and [Cu(en)₂](3-pyt)₂ (2), derived from potassium [N′-(pyridine-3-carbonyl)-hydrazinecarbodithioate [K⁺(H₂L)⁻] and containing en as a co-ligand, have been synthesized. The [K⁺(H₂L)⁻] undergoes cyclization in the presence of ethylenediamine (en) and is converted to 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione (3-pyt)⁻. [Ni(en)₂(3-pyt)₂] and [Cu(en)₂](3-pyt)₂ have been characterized with the aid of elemental analyses, IR, UV–Vis, magnetic susceptibility and single crystal X-ray studies. The complexes 1 and 2 crystallize in the orthorhombic and monoclinic systems with space groups Pca2(1) and C2/c, respectively. The single crystal X-ray diffraction studies of both complexes indicate that (3-pyt)⁻ adopts a thione form in 1 but is present as a thiolato form in 2.     

Supramolecular complexes constructed with carboxylate Cu(II) and 2-(2-pyridyl)-benzimidazole via hydrogen bonding

Four copper(II) supramolecular complexes, {[Cu(Hpb)(mal)]·H₂O} _n (1), (Hpb?=?2-(2-pyridyl)-benzimidazole, mal?=?maleate), [Cu₄(pb)₄(cro)₄(MeOH)₂]·2MeOH (2) (cro?=?crotonate), [Cu₂(pb)(Hpb)(mac)₃(MeOH)] (3) (mac?=?α-methacrylate) and [Cu(Hpb)(acr)₂(H₂O)] (4) (acr?=?acrylate), based on carboxylate copper(II)-aromatic ligand systems which are assembled by combination of metal coordination, hydrogen-bond and π–π interactions, have been rationally designed and synthesized. Complex 1 forms a 3D supramolecular network with open channels by extending 2D undulating sheets constructed from 1D helical chains. Complex 2 generates a 2D grid-like sheet via unusual finite-chain tetranuclear molecules, with four copper atoms arranged in a line; the unit does not extend further due to the capping effect of the terminal methanol. Complexes 3 and 4 present a 1D sinusoidal structure and a 3D columnar network with 1D ladder-shaped double chains, respectively. Interestingly, coligand Hpb, deprotonated or/and neutral in different supramolecular complexes, provides hydrogen bonding and π–π stacking interactions. In complexes 2, 3 and 4, carboxylate anions show various bridging modes, which are reflected in their magnetic properties. Weak ferromagnetic coupling (syn-anti µ-OCO) exists in 1, antiferromagnetic (syn-syn µ-OCO) and weak ferromagnetic coupling (µ-O of the??COO group) in 2 and antiferromagnetic coupling (syn-syn µ-OCO) in 3.     

Syntheses and characterization of new MnII and FeII complexes with 4′-(4-pyridyl)-2,2′ : 6′,2″-terpyridine (pyterpy), [Mn(pyterpy)(MeOH)2(OAc)](ClO4) and [Fe(pyterpy)2](SCN)2 · MeOH

Two new Mn^II and Fe^II complexes with 4′-(4-pyridyl)-2,2′ : 6′,2″-terpyridine (pyterpy), [Mn(pyterpy)(MeOH)₂(OAc)](ClO₄) (1) and [Fe(pyterpy)₂](SCN)₂ · MeOH (2) have been synthesized and characterized by CHN elemental analysis, IR spectroscopy, and structurally analyzed by single-crystal X-ray diffraction. The thermal stabilities of these compounds were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The potentially tetradentate pyterpy ligand is a tridentate donor to both Mn(II) and Fe(II). The non-coordinated pyridyl interacts via O–H ··· N and C–H ··· N hydrogen bonds with adjacent molecules in 1 and 2, respectively, to form inversion symmetric dimers. Compound 1 is further extended into infinite hydrogen bonded chains via pairs of O–H ··· O_acetate hydrogen bonds.     

Construction of C(sp2)−C(sp3) Bond between Quinoxalin‐2(1H)‐ones and N‐Hydroxyphthalimide Esters via Photocatalytic Decarboxylative Coupling

A novel visible‐light‐driven decarboxylative coupling of alkyl N‐hydroxyphthalimide esters (NHP esters) with quinoxalin‐2(1H)‐ones has been developed. This C(sp²)?C(sp³) bond‐forming transformation exhibits excellent substrate generality with respect to both the coupling partners. Of note, a series of 3‐primary alkyl‐substituted quinoxalin‐2(1H)‐ones that were difficult to synthesize by previous methods could be obtained in moderate to excellent yields. Additionally, the mild conditions, easy availability of substrates, wide functional group tolerance and operational simplicity make this protocol practical in the synthesis of 3‐alkylated quinoxalin‐2(1H)‐ones.