2-Acetylpyridine- and 2-benzoylpyridine-derived thiosemicarbazones and their antimony(III) complexes exhibit high anti-trypanosomal activity

Complexes [Sb(2Ac4oClPh)Cl₂] (1), [Sb(2Ac4oFPh)Cl₂] (2), [Sb(2Ac4oNO₂Ph)Cl₂] (3), [Sb(2Bz4oClPh)Cl₂] (4), [Sb(2Bz4oFPh)Cl₂] (5) and [Sb(2Bz4oNO₂Ph)Cl₂] (6) were obtained with 2-acetylpyridine-N(4)-ortho-chlorophenyl thiosemicarbazone (H2Ac4oClPh) and its N(4)-ortho-fluor (H2Ac4oFPh) and N(4)-ortho-nitro (H2Ac4oNO₂Ph) analogues, and with the corresponding 2-benzoylpyridine-derived thiosemicarbazones (H2Bz4oClPh, H2Bz4oFPh, H2Bz4oNO₂Ph). The studied compounds are excellent inhibitors of Trypanosoma cruzi growth. H2Bz4oClPh and complexes (4) and (1) were the most trypanosomicidal.Upon coordination of H2Ac4oClPh to antimony(III) in 1, the therapeutic index (TI) goes from 10.58 to 14.35. However, the best values of TI were found for H2Bz4oClPh (TI = 1240) and H2Ac4oNO₂Ph (TI = 773). Structure-activity relationship (SAR) studies did not allow the establishment of correlations between the anti-trypanosomal activity and physico-chemical parameters, but correlations were found between the cytotoxicities and physico-chemical properties.     

Solid-state structure determination and solution-state NMR characterization of the (2R,4R)/(2S,4S)- and (2R,4S)/(2S,4R)-diastereomers of the agricultural fungicide propiconazole,the (2R,4S)/(2S,4R)-symmetrical triazole constitutional isomer,and a ditriazole analogue

Single-crystal X-ray diffraction analysis was used to determine the structure of a racemic diastereomer of the agricultural fungicide propiconazole [1-(2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole] and of two by-products (a symmetrical 1,3,4-triazole racemic-constitutional isomer and a propiconazole ditriazole analogue). All three crystalline racemic-diastereomers had (2R,4S)/(2S,4R)-stereochemistry in which then-propyl group was observed in atrans-to-phenyl disposition. Propiconazole (2R,4S)/(2S,4R)-diastereomer gives crystals belonging to the monoclinic space group P2₁,/a, and, at 293 K,a=8.1192(3),b=18.9769(6),c=10.7137(4) å,Β=99.765(3)?,V=1626.8(1) å³, Z=4,R(F)=0.060, andR _w(F)=0.058. The constitutional isomer by-product (2R,4S)/(2S,4R)-1-(2-(2,4-dichlorophenyl)-4-n-pro-pyl-1,3-dioxolane-2-yl-methyl)-1-H-1,3,4-triazole gives crystals belonging to the monoclinic space group P2₁/n, and, at 293 K,a=11.1763(6),b=10.7716(4),c=14.5804(8) å,Β=107.445(4)?,V=1674.6(1) å³, Z=4,R(F)=0.043, andR _w(F)=0.043. The ditriazole byproduct (2R,4S)/(2S,4R)-1-(2-(2-chloro-4-(1,2,4-triazole-1-yl)phenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole gives crystals belonging to the triclinic space groupP¯ 1, and, at 193 K,a=5.3329(8),b=8.3738(7),c=20.240(2) å, α=84.213(6)?,Β=87.20(1)?,γ=86.23(1)?,V=896.5(2) å³, Z=2,R(F)=0.046, andR _w(F)=0.051. The presence of both propiconazole (2R.4S)- and (2S,4R)-enantiomers enables the formation of a crystalline racemic modification, while the diastereomeric propiconazole (2R,4R)- and (2S,4S)-enantiomers are viscous oils. In the absence of its enantiomorphic partner, the propiconazole (2R,4S)- or (2S,4R)-enantiomers remain as viscous oils rather than form chiral crystals.     

Ligand assisted homolytic cleavage of the Ru-Ru single bond in [Ru2(CO)4] core and the chemical consequence

The Ru-Ru single bond in [Ru₂(CO)₄(MeCN)₆][BF₄]₂ remains intact in the reaction with 2-i-propyl-1,8-naphthyridine (ⁱPrNP) and the isolated product is the cis-[Ru₂(ⁱPrNP)₂(CO)₄(OTf)₂] (1) obtained via crystallization in the presence of [n-Bu₄N][OTf]. The 2-t-butyl-1,8-naphthyridine (^tBuNP), on the contrary, leads to the oxidative cleavage of the Ru-Ru single bond resulting in the trans-[Ru(^tBuNP)₂(MeCN)₂][BF₄]₂[NC(Me)C(Me)N] (2). The anti-[NC(Me)C(Me)N]²⁻ is the product of the two-electron reductive coupling of two acetonitrile molecules. The phenoxo appendage in 2-(2-hydroxyphenyl)-1,8-naphthyridine (hpNP) brings the identical effect of the scission of the Ru-Ru bond but the process is non-oxidative and the product obtained is the cis-[Ru(hpNP)₂(CO)₂][BF₄] (3). The bis-(diphenylphosphino)methane (dppm) in dichloromethane oxidatively cleave the Ru-Ru bond leading to chloro bridged [Ru(μ-Cl)(dppm)(CO)(MeCN)]₂[BF₄]₂ (4). All the complexes have been characterized by the spectroscopic and electrochemical measurements and their structures have been established by X-ray diffraction study.     

Synthesis, crystal structure, and vibrational spectra of MVO(SO4)2 (M = Rb, Cs, or Tl)

A series of MVO(SO₄)₂ vanadium complexes, where M = Rb, Cs, or Tl, were prepared, and their crystal structures and physicochemical properties studied. The rubidium and thallium compounds of this series were found to be isostructural to each other and to crystallize, like KVO(SO₄)₂ and NH₄VO(SO₄)₂, in orthorhombic system (space group P2₁2₁2₁, No. 19, Z = 4) with the unit cell parameters a = 4.9735(2) Å, b=8.7894(4) Å, c = 16.6968(8) Å, V = 729.88 ų (Rb); and a = 4.9636(1) Å, b = 8.7399(2) Å, c = 16.8598(4) Å, V = 731.39 ų (Tl). The cesium compound was found to crystallize in monoclinic system (space group P2₁/a, No. 14-2, Z = 4): a = 10.0968(6) Å, b = 8.9131(4) Å, c = 9.8675(5) Å, β = 114.640(2)°, V = 807.16 ų. The MVO(SO₄)₂ crystal structure is built of VO₆ octahedra, which are linked into layers by bridging SO₄ groups. At the apex of each VO₆ octahedron, there is a short V-O terminal bond having a length of 1.54(1) Å (Rb), 1.57(2) Å (Tl), and 1.52(4) Å (Cs).     

Preliminary studies on a novel synthesis of β-amino acids: stereocontrolled transformation of d- and l-glyceraldehyde into 3-amino-2-(2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoic acids

A stereocontrolled synthesis of the methyl ester of (2S)-3-amino-2-((4′S)-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoic acid from d-glyceraldehyde is described for the first time. This method involves the stereoselective Michael addition of the lithium salt of tris(phenylthio)methane to (S)-2,2-dimethyl-4-((E)-2-nitrovinyl)-1,3-dioxolane followed by hydrolysis of the resulting (4S)-2,2-dimethyl-4-((2′S)-3′-nitro-1′,1′,1′-tris(phenylthio)propan-2′-yl)-1,3-dioxolane to (2S)-methyl 2-((4′S)-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-3-nitropropanoate, which was finally reduced to the target compound. A similarly stereocontrolled transformation of l-glyceraldehyde into (2R)-methyl 3-amino-2-((4′R)-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoate is also described.     

Preparation and Crystal Structures of 4-(4′-Pyridylthio)-1-methylpyridinium Salts: Assembly of a Donor-Acceptor-Type Molecule Containing a Sulfide Bridge

A series of ionic 4-(4′-pyridylthio)-1-methylpyridinium salts with different counteranions (1, I⁻; 2, BF⁻₄; 3, PF⁻₆; and 4, OTf⁻, where OTf=trifluoromethanesulfonate) have been prepared. Structural analysis reveals that the cation exhibits a variety of stacking structures dependent on the anion. Compound 1 crystallizes in space group P2_1/n (#14), with a=10.764(3) Å, b=9.601(5) Å, c=13.105(3) Å, β=108.35(2), V=1285.4(8) ų, and Z=4. In this compound, each cation moiety is stacked in a helical arrangement along the c-axis. Compound 2, which is isomorphous to 1, has space group P2_1/n (#14), with a=11.647(2) Å, b=9.203(3) Å, c=13.232(2) Å, β=108.42(2), V=1345.6(5) ų, and Z=4. Compound 3 crystallizes in space group P2_1/n (#14), with a=8.06(1) Å, b=17.43(1) Å, c=10.30(1) Å, β=103.0(1), V=1410(3) ų, and Z=4. In this salt, the cation molecules assume a head-to-tail stacking arrangement, forming a polar pseudo 1-D chain. Compound 4 crystallizes in space group Pb? (#2), with a=7.585(4) Å, b=15.443(7) Å, c=6.775(4) Å, α=99.33(4), β=108.35(2)^o, γ=98.37(4), V=756.6(7) ų, and Z=2. The structure of 4 consists of a columnar stacking of pyridine moieties, with the cation moieties surrounded by the counteranions. Calculations show that the 4-(4′-pyridylthio)-1-methylpyridinium cation may be a good building block for second harmonic generation (SHG) materials, even though salts 1-4 crystallized in centrosymmetric structures and were SHG inactive.     

Syntheses and single-crystal structures of CsTh(MoO4)2Cl and Na4Th(WO4)4

Colorless crystals of CsTh(MoO₄)₂Cl and Na₄Th(WO₄)₄ have been synthesized at 993 K by the solid-state reactions of ThO₂, MoO₃, CsCl, and ThCl₄ with Na₂WO₄. Both compounds have been characterized by the single-crystal X-ray diffraction. The structure of CsTh(MoO₄)₂Cl is orthorhombic, consisting of two adjacent [Th(MoO₄)₂] layers separated by an ionic CsCl sublattice. It can be considered as an insertion compound of Th(MoO₄)₂ and reformulated as Th(MoO₄)₂·CsCl. The Th atom coordinates to seven monodentate MoO₄ tetrahedra and one Cl atom in a highly distorted square antiprism. Na₄Th(WO₄)₄ adopts a scheelite superlattice structure. The three-dimensional framework of Na₄Th(WO₄)₄ is constructed from corner-sharing ThO₈ square antiprisms and WO₄ tetrahedra. The space within the channels is filled by six-coordinate Na ions. Crystal data: CsTh(MoO₄)₂Cl, monoclinic, P2₁/c, Z=4, a=10.170(1) Å, b=10.030(1) Å, c=9.649(1) Å, β=95.671(2)°, V=979.5(2) Å³, R(F)=2.65% for I>2σ(I); Na₄Th(WO₄)₄, tetragonal, I4₁/a, Z=4, a=11.437(1) Å, c=11.833(2) Å, V=1547.7(4) Å³, R(F)=3.02% for I>2σ(I).     

Defects and Luminescence Behavior of Cubic F23 [(NH4(18-Crown-6))4MnX4] [TlX4]2 (X=Cl, Br) Crystals

Luminescence from [(NH₄(18-Crown-6))₄MnBr₄][TlBr₄]₂ (1), [(NH₄(18-Crown-6))₄MnCl₄][TlCl₄]₂ (2), [(NH₄(18-Crown-6))₂MnBr₄] (3), and [(NH₄(18-Crown-6))₂MnCl₄] (4) was studied in search of new insights regarding crystal defects in 2. Emission from 3 and 4 is normal Mn²⁺(⁴T₁(⁴G)→⁶A₁); that of 2 (λ_max≈520 nm at ca. 300 K and 560 nm at 77 K) is unusual and temperature dependent. Thermal barriers (kJ/mol, assignment): green emission of 1 and 2, T<150 K (1-2, NH⁺₄ rotations), 150<T<250 K (7-14, energy migration among [MnX₄]²⁻), 250<T<300 K (26-35, rotations of 18-Crown-6)); yellow emission of 2: T;<250 K (7-8, energy migration among [MnX₄]²⁻), T>250 K (29 kJ/mol, defect-to-Mn²⁺(⁴T₁(⁴G)) back energy transfer). Crystal data for 4: Space group P2₁/c; Z=4; a=20.173(1) Å; b=9.0144(8) Å; c=20.821(1) Å; β=98.782(5)°; V=3741.9(8) ų; R_w=0.059; R=0.054.     

Structures and syntheses of framework triuranyl diarsenate hydrates

Two homeotypic hydrated uranyl arsenates, (UO₂)[(UO₂)(AsO₄)]₂(H₂O)₄, UAs4, and (UO₂)[(UO₂)(AsO₄)]₂(H₂O)₅, UAs5 were synthesized by hydrothermal methods. Intensity data were collected at room temperature using MoKα X-radiation and a CCD-based area detector. Their crystal structures were solved by direct methods and refined by full-matrix least-squares techniques on the basis of F² to agreement indices (UAs4, UAs5) wR₂=0.116, 0.060, for all data, and R₁=0.046, 0.033, calculated for 3176, 5306 unique observed reflections (|F_o|>4σ_F) respectively. UAs4 is monoclinic, space group P2₁/c, Z=4, a=11.238(1), b=7.152(1), c=21.941(2)Å, β=104.576(2)°, V=1706.8(1)ų, D_calc=4.51 g/cm³. UAs5 is orthorhombic, space group Pca2₁, Z=4, a=20.133(2), b=11.695(1), c=7.154(1)Å, V=1684.4(1)ų, D_calc=4.65 g/cm³. Both structures contain sheets of arsenate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO₂)(AsO₄)]¹⁻ and the uranophane sheet anion-topology. The sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with an arsenate tetrahedron on each of two adjacent sheets, resulting in open-frameworks with isolated H₂O groups in the larger cavities of the structures. The uranyl arsenate sheet in UAs4 is relatively planar, and is topologically identical with the uranyl phosphate sheet in (UO₂)[(UO₂)(PO₄)]₂(H₂O)₄. The uranyl arsenate sheet in UAs5 is the same geometrical isomer as in UAs4, but is highly corrugated, exhibiting approximately right angle bends of the sheet after every second uranyl arsenate chain repeat.     

Synthesis, Crystal and Magnetic Structures of the Sodium Ferrate (IV) Na4FeO4 Studied by Neutron Diffraction and Mössbauer Techniques

The alkali sodium ferrate (IV) Na₄FeO₄ has been prepared by solid-state reaction of sodium peroxide Na₂O₂ and wustite Fe_1−xO, in a molar ratio Na/Fe=4, at 400°C under vacuum. Powder X-ray and neutron diffraction studies indicate that Na₄FeO₄ crystallizes in the triclinic system P−1 with the cell parameters= a=8.4810(2) Å, b=5.7688(1) Å, c=6.5622(1) Å, α=124.662(2)°, β=98.848(2)°, γ=101.761(2)° and Z=2. Na₄FeO₄ is isotypic with the other known phases Na₄MO₄ (M=Ti, Cr, Mn, Co and Ge, Sn, Pb). The solid solution Na₄Fe_xCo_1−xO₄ exists for x=0-1 and we have followed the evolution of the cell parameters with x to determine the lattice parameters of the triclinic cell of Na₄FeO₄. A three-dimensional network of isolated FeO₄ tetrahedra connected by Na atoms characterizes the structure. This compound is antiferromagnetic below T_N=16 K. At 2 K the magnetic cell is twice the nuclear cell and the magnetic structure is collinear (μ_Fe=3.36(12) μ_B at 2 K). This black compound is highly hygroscopic. In water or on contact with the atmospheric moisture it is disproportionated in Fe³⁺ and Fe⁶⁺. The Mössbauer spectra of Na₄FeO₄ are fitted with one doublet (δ=− 0.22 mm/s, Δ=0.41 mm/s at 295 K) in the paramagnetic state and with a sextet at 8K. These parameters characterize Fe⁴⁺ high-spin in tetrahedral FeO₄ coordination.     

Synthesis and characteristics of the dioxonium salt based on tartratogermanate acid. Crystal and molecular structure of (H5O2)[(H2O)2Ge(μ-Tart)2Ge(OH)] · 4H2O

Tartratogermanate acid was obtained for the first time as the dioxonium complex (H₅O₂)[(H₂O)₂Ge(??-Tart)₂Ge(OH)] · 4H₂O (I) by the reaction of germanium tetrachloride with D-tartaric acid (H₄Tart) in 85% acetic acid. The complex was characterized by elemental analysis data, thermogravimetry, and IR spectroscopy. X-ray diffraction analysis for I was performed. The crystals are orthorhombic, a = 15.862(3) ?, b = 13.401(3) ?, c = 8.6800(17) ?, V = 1845.1(6) ?³, Z= 4, space group P2₁2₁2, R1= 0.0520 for 5152 reflections with I > 2??(I). Compound I is composed of the dimeric complex anions [(H₂O)₂Ge(??-Tart)₂Ge(OH)]^?, dioxonium cations, and water molecules of crystallization. In the anion, the Ge(1) (CN = 6) and Ge(2) (CN = 5) atoms are linked by two chelating bridging fully deprotonated tartaric acid ligands through two carboxyl (average Ge-O, 1.883(4) and 1.893(4) ?, respectively) and two alcohol (average Ge-O, 1.859(4) and 1.779(4) ?, respectively) oxygen atoms. The coordination polyhedron of Ge (1) is completed to a distorted octahedron by the oxygen atoms of two water molecules (Ge(1)-O(H₂O), 1.933(4) and 1.854(3) ?). The Ge(2) coordination polyhedron is trigonal bipyramid. Its base is formed by two alcohol oxygen atoms of two bridging Tart^4? ligands and the oxygen atom of the terminal hydroxy group (Ge-O, 1.764(4) ?). The axial positions are occupied by the carboxyl oxygen atoms of the Tart^4? ligands (the O(5)Ge(2)O(11), 176.84(16)°). In the crystal, the structural units are combined by hydrogen bonds to a three-dimensional framework.     

Derivatives of α,β-dehydro amino acids: VI. Reaction of 4-benzylidene-2-phenyl-1,3-oxazol-5(4H)-one with piperidin-2-ylmethanamine

4-Benzylidene-2-phenyl-1,3-oxazol-5(4H)-one reacts with piperidin-2-ylmethanamine to give N-{(Z)-3-oxo-3-[(piperidin-2-ylmethyl)amino]-1-phenylprop-1-en-2-yl}benzamide, N-(4-benzyl-3-oxooctahydro-2N-pyrido[1,2-a]pyrazin-4-yl)benzamide, or/and (Z)-4-benzylidenehexahydro-2H-pyrido[1,2-a]pyrazin-3(2H)-one, depending on the solvent, temperature, and reaction time. The latter product is formed via three-step tandem process.     

Crystal structure of potassium 2-thiobarbiturate

The crystal and molecular structure of potassium thiobarbiturate C₄H₃KN₂O₂S (C₄H₄N₂O₂S-2-thiobarbituric acid, H₂TBA) is determined. Crystallographic data for KHTBA are as follows: a = 11.2317(17) Å, b = 3.8687(6) Å, c = 14.557(2) Å, β = 97.448(4)°, V = 627.18(17) ų, space group P2/c, Z = 4. Each potassium ion is linked with four oxygen atoms and two S atoms forming a distorted octahedron. N-H…O and C-H…S hydrogen bonds form a branched three-dimensional network. The structure is also stabilized by the π-π interaction of heterocyclic HTBA^? ions.     

Fine tuning of the structure of phosphine–phosphoramidites: application for rhodium-catalyzed asymmetric hydrogenations

Diastereomers of (4-(diphenylphosphino)pentan-2-yl)-N-isopropyl-{dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxa-phosphepin-2-yl}-4-amine, (S)-(2S,4S)-1, and (S)-(2R,4R)-3; the octahydro derivative 4 of (S)-(2S,4S)-1, and derivative 2 of (S)-(2S,4S)-1 containing a 1,3-propanediyl backbone, have been synthesized and used for rhodium-catalyzed asymmetric hydrogenations of prochiral olefins in order to study the role of the stereogenic elements in the backbone and in the terminal moiety. The central chirality in the bridge has been found to determine the configuration of the product with a cooperative effect from the terminal groups. Excellent ee’s (up to 99.9%) were obtained in the hydrogenation of methyl (Z)-α-acetamidocinnamate using a rhodium complex with the matched arrangement (S)-(2S,4S)-1. The hydrogenation is accomplished in a highly enantioselective manner by using green solvents such as propylene carbonate.     

Two Ce(SO4)2·4H2O polymorphs: Crystal structure and thermal behavior

Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO₄)₂·4H₂O are reported. The first modification, α-Ce(SO₄)₂·4H₂O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO₄)₂·4H₂O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H₂O)₄(SO₄)₂ held together by a hydrogen bonding network. The dehydration of Ce(SO₄)₂·4H₂O is a two step (I) and one step (II) process, respectively, forming Ce(SO₄)₂ in both cases. During the decomposition of the anhydrous form, Ce(SO₄)₂, into the final product CeO₂, intermediate xCeO₂·yCe(SO₄)₂ species are formed.     

Tin(IV) complexes with 2-pyridineformamide-derived thiosemicarbazones: Antimicrobial and potential antineoplasic activities

Reaction of tin tetrachloride with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives gave [Sn(2Am4DH)Cl₃] (1), [Sn(2Am4Me)Cl₃] (2), [Sn(2Am4Et)Cl₃] (3) and [Sn(2Am4Ph)Cl₃] (4) as products, in which an anionic thiosemicarbazone coordinates to the metal centre along with three chloride ions. The crystal structures of 1 and 2 were determined. The thiosemicarbazones were moderately active against Candida albicans and Pseudomonas aeruginosa. Upon coordination to tin(IV) the antimicrobial activity of the thiosemicarbazones increases. The studied compounds proved to be toxic to Artemia salina, suggesting that they could present cytotoxic activity against solid tumors.     

Synthesis of molecular chains: phenylene thioether and sulfoxide oligomers

The application of a general synthetic approach to prepare molecular chains is reported. It is based on a step-by-step method each consisting first in a Pd-catalyzed reaction between ArI and HXAr′Br (Ar=aryl, Ar′=arylene) to give ArXAr′Br followed by a Cu-catalyzed replacement of Br by I to give ArXAr′I that can be reacted with HXAr′Br in the following step. The application of this method is here illustrated to prepare phenylene sulfide oligomers (X=S). Starting from RC₆H₄I-4 (R=H, MeO, NO₂, NH₂) and HSC₆H₄Br-x (x=2, 4) it is possible to grow chains in one direction to give X(C₆H₄S-m)_nC₆H₄R-4 (n=1, X=Br, m=4, R=H, MeO, NO₂, NH₂, SMe and m=2, R=H, MeO, NO₂; n=1, X=I, m=2 or 4, R=H, MeO, NO₂; n=2, X=Br, m=2 or 4, R=H, MeO, NO₂; n=2, X=I, m=4, R=MeO, NO₂; n=3, X=Br, m=4, R=MeO, NO₂; n=3, X=I, m=4, R=NO₂ and n=4, X=Br or I, m=4, R=NO₂). From HSC₆H₄Br-x and IC₆H₄I-4 the chains can grow in two directions to give X(C₆H₄S-4)_nC₆H₄X-4 (n=2 or 4, X=Br or I), 2-XC₆H₄(SC₆H₄-4)_nSC₆H₄X-2 (n=3 or 5, X=Br). Using diiodomesitylene the dithioethers C₆HMe₃-2,4,6-(SC₆H₄X-4)₂-1,3 (X=Br, I) have been prepared. The series of sulfoxides X(C₆H₄S(O)-4)_nC₆H₄R-4 (X=Br, n=1, R=MeO, n=3, R=NO₂, n=4, R=Br; X=R=I, n=2) has been obtained from the corresponding thioethers and PhICl₂.     

Molybdenum carbonyl complexes of binucleating pyridine-based ligands

Reaction of [Mo(CO)₄(diene)] with 4,4′-bipyridine (44′B), trans-1,2-bis(2-pyridyl)ethene (2-bpe) and trans-1,2-bis(4-pyridyl)-ethene (4-bpe) gives polymeric [Mo(CO)₄(44′B)]_n, mononuclear cis-[Mo(CO)₄(2-bpe)₂] and binuclear [Mo(CO)₄(4-bpe)]₂ respectively. Reaction of the same ligands with [Mo(CO)₄(bpy)] (bpy is 2,2′-bipyridine) produces the bridged binuclear complexes [{Mo(CO)₃(bpy)}₂(44′B)] and [{Mo(CO)₃(bpy)}₂(4-bpe)]. Products are characterised by microanalysis and spectroscopy (IR, ¹H NMR, UV/vis). Reduction of [{Mo(CO)₃(bpy)}₂(44′B)] produces an anion in which the unpaired electron is localised on the chelating bpy ligand.     

Preparation of (2E,4E)-2-(2-benzyloxyethyl)-5-(3-methoxy-4-chlorophenyl)penta-2,4-dienal as a key intermediate in the synthesis of strobilurin B

(2E,4E)-2-(2-Benzyloxyethyl)-5-(4-chloro-3-methoxyphenyl)penta-2,4-dienal was obtained by the condensation of 4-benzyloxybutanal N-tert-butylimine with 4-chloro-3-methoxycinnamic aldehyde with ≥98% configurational purity and 40% yield. When 4-benzyloxy-2-triethylsilylbutanal imine was used, a 7: 3 mixture of the target (2E,4E)-dienal with its (2Z,4E)-isomer was obtained in 60% yield; the latter quantitatively isomerized to the thermodynamically preferable target (2E,4E)-dienal.     

Asymmetric synthesis of isoquinuclidines by Diels–Alder reaction of 1,2-dihydropyridine utilizing a chiral Lewis acid catalyst

The chiral isoquinuclidine derivative, 2-azabicyclo[2.2.2]octane ring system, endo-(7R)-3 was obtained in good yield with excellent diastereoselectivity (up to 92% de) by Diels–Alder reaction of 1-(phenoxycarbonyl)-1,2-dihydropyridine 1 with N-acryloyl-(4S)-4-benzyloxazolidin-2-one (4S)-2 using titanium-(2R,3R)-TADDOLate 4 as a chiral Lewis acid catalyst in toluene at 0 °C. On the other hand, endo-(7S)-3 was obtained in good yield with excellent diastereoselectivity (up to 97% de) by Diels–Alder reaction of 1 with (4R)-2 using Cu(OTf)₂/(4S,4′S)-bis(oxazoline) catalyst 8 as a chiral Lewis acid catalyst in dichloromethane at 0 °C. In these reactions, the choice of solvent and the combination of titanium-(2R,3R)-TADDOLate 4 {or Cu(II)/(4S,4′S)-bis(oxazoline) 8} and dienophile (4S)-2 {or (4R)-2} are very important. The stereochemistry of endo-(7R)-3 has been established to be (1R,4S,7R) and the reaction mechanism is proposed.