Carbon-nitrogen bond formation in the reaction of the reaction of diphenyl diazomethane Ph2 CN2 with diiron-carbene complexes (Fe2(CO)7x03BD;-C(R)C(NEt2)x03BD;-C(R)C(NEtx03BC;-C(R)C(NEt2)N(NCPh2)x03BC;-C(R)C(NEtx03BC;-C(R)C(NEt2)NN(CPh2)x03BC;-C(R)C(NEt)]

The diiron ynamine complex [Fe₂(CO)₇{μ-CR)C(NEt₂)}] (1:R=Me,2:R = C₃H₅.3:R=SiMe₃.4:R = Ph) reacts at room temperature with diphenyldiazomethane Ph₂CN₂, in hexane to yield complexes [Fe₂(CO)₆{C(R)C(NEt₂)N (NCPh₂)] (5a:R=Me,6a:R=C₃H₅.7a R=SiMe₃.8a:R=Ph) resulting from the insertion of the terminal nitrogen atom into the Fe=C carbene bond. Insertion the second nitrogen atom and formation of compounds [Fe₂(CO)₆zμ-C(R)C(NEt₂)NN(CPh₂)}] (5b:R=Me,6b:R=C₃H₅,7b:R=SiMe₃,8b:R=Ph) is observed when compounds5a-5a are treated in refluxing hexane. Transformation of compoundsa tob is also obtained at room temperature within a few days. All compounds were identified by their¹H NMR spectra. Compounds6a, 7a, 8a, and8b were characterized by single crystal X-ray diffraction analyses. Crystal data: for6a: space group = P2₁/n,a=12.853(1) A,b=24.800(7) A,c=8.947(6) A,β=99.29(3)°,Z=4, 2227 rellectionsR=0,038; for7a: space group=Pl,a=ll.483(4) A,b=14.975(4) A,c = 17.890(8) A,α = 82.80(3)°,β=94.29(7)°,γ=85.42(2),Z = 4, 5888 reflectionR = 0.035: for8a: space group = Pcab.a = 31.023(8) A.b=20.137(1) A.c=9.686(2) A.Z=8. 1651 reflections,R=0.071; for8b: space group=P2₁/n,a=21.459(4),b=10,100(3) A,c=28,439(8) A,ß=103.86(4)°,Z=8. 2431 reflections.R=0.057.     

Nucleophilic substitution reactions of acetylides on substituted tricarbonyl(η6-fluoroarene)chromium and reactions of tricarbonyl[η6-(2-trimethylsilylethynyl)toluene]chromium and tricarbonyl[η6-(p-ethynyl-phenylethynyl)benzene]chromium with dicobalt octacarbonyl

Nucleophilic substitution reactions of various acetylides on substituted tricarbonyl(η⁶-fluoroarene)chromiums were pursued. The reaction presumably underwent a more complicated mechanism rather than the direct substitution on the fluorine-bearing carbon. The organometallic compounds (η⁶-C₆H₃R¹R²R³)Cr(CO)₃ (R¹: CC–C₆H₄CH₃, R²: o-Me, R³: H (5a), R¹: CC–C₆H₄CH₃, R²: o-OMe, R³: H (6a), R¹: CC–C₆H₄CH₃, R²: m-OMe, R³: H (6b), R¹: CCPh, R²: o-Me, R³: o-OMe (8b), R¹: CCPh, R²: m-Me, R³: m-OMe (8c), R¹: CCSiMe₃, R²: o-Me, R³: H (9a), R¹: CC–C₆H₄CCH, R²: H, R³: H (12), R¹: CC–C₆H₄CCH, R²: o-Me, R³: H (13)) as well as the organometallic dimmer [{(η⁶-o-Me-C₆H₄)Cr(CO)₃(di-ethynyl)] (di-ethynyl: CC–C₆H₄CC (14)) have been synthesized from nucleophilic substitution reactions of tricarbonyl(η⁶-fluoroarene)(chromium) compounds with suitable acetylides. The products have been characterized by spectroscopic means. In addition, (8b) and (8c) were characterized by X-ray diffraction studies. Further reactions of (9a) and (12) with appropriate amount of Co₂(CO)₈ yielded μ-alkyne bridged bimetallic complexes, Co₂(CO)₆{μ-Me₃SiCC–(o-tolueneCr(CO)₃} (10) and (Co₂(CO)₆)₂{μ-HCC–C₆H₄–CC–(benzene)Cr(CO)₃)}(15), respectively. Both (10) and (15) were characterized by spectroscopic means as well as single crystal X-ray crystallography. The core of these molecules is quasi-tetrahedron containing a Co₂C₂ unit. A two-dicobalt-fragments coordinated di-enyls complex, (Co₂(CO)₆)₂{μ-HCC–C₆H₄–CC–H} (17), was synthesized from the reaction of 1,3-diethynylbenzene with Co₂(CO)₈. Crystallographic studies of (17) also show that it exhibits a distorted Co₂C₂ quasi-tetrahedral geometry.     

Synthesis of enantiomerically pure spiro-cyclopropane derivatives containing multichiral centers

A novel chiral source, 5-(R)-[(1R,2S,5R)-(−)-menthyloxy]-3-bromo-2(5H)-furanone (5a), was obtained in 46% yield with d.e.≥98% from the epimeric mixture of 5-(l-menthyloxy)-3-bromo-2(5H)-furanone (5a+5b) obtained via the bromination of an epimeric mixture of 5-(l-menthyloxy)-2(5H)-furanone (3a+3b) followed by the elimination of hydrogen bromide. The asymmetric reaction of 5a with a nucleophilic alcohol afforded enantiomerically pure spiro-cyclopropane derivatives containing four stereogenic centers, 9a–9e, in 50–68% yield with d.e.≥98%. The enantiomerically pure compounds 9a–9e were identified on the basis of their analytical data and spectroscopic data, such as [α]_D²⁰, UV, IR, ¹H NMR, ¹³C NMR, MS and elementary analysis. The absolute configuration of the chiral spiro-cyclopropane compound 9a was established by X-ray crystallography.     

Stereocontrolled synthesis of enantiomerically pure unsaturated analogues of 2,6-DAP. Part 5

An efficient new stereocontrolled synthesis of (2R,6R)-(+)- and (2S,6S)-(−)-2,6-diamino-4-methylene-1,7-heptanedioic acid 8a and 9a, respectively, has been accomplished starting from the glycine-derived chiral synthon 1. The enantiomerically pure α-alkyl derivatives 8b–d and 9b–d have also been synthesized. The absolute configuration of the new stereocenters was assigned on the basis of ¹H NMR spectra.     

Preparation of (1R,8S)- and (1S,8R)-9-azabicyclo[6.2.0]dec-4-en-10-one: potential starting compounds for the synthesis of anatoxin-a

9-Azabicyclo[6.2.0]dec-4-en-10-one (±)-2, obtained from cyclooctadiene by addition of chlorosulfonyl isocyanate, was N-hydroxymethylated to (±)-3 and then resolved by lipase-catalysed asymmetric acylation of the primary OH group at the (S)-stereogenic centre. High enantioselectivity (E=94) was observed when lipase PS and vinyl butyrate were used in di-iso-propyl ether at −15°C, resulting in the enantiomerically enriched ester 3a and alcohol 3b (e.e. ≥92%). Treatment of 3a and 3b with NH₄OH/MeOH afforded the corresponding β-lactams (1R,8S)-2a and (1S,8R)-2b (e.e. ≥93%), potential starting compounds in anatoxin-a synthesis. The ring opening of lactams (±)-2, (±)-7, 3a and 3b, followed by reduction, resulted in racemic 4–6 and 8 and enantiomeric 4a, 4b, 5a and 5b eight-membered cyclic β-amino acid derivatives.     

Chelating diamide complexes of titanium: new catalyst precursors for the highly active and living polymerization of α-olefins

The reaction of RHN(CH₂)₃NHR (1a,b) (a, R=2,6-ⁱPr₂C₆H₃; b, R=2,6-Me₂C₆H₃) with 2 equiv of BuLi followed by 2 equiv of ClSiMe₃ yields the silylated diamines R(Me₃Si)N(CH₂)₃N(SiMe₃)R (3a,b). The reaction of 3a,b with TiCl₄ yields the dichloride complexes [RN(CH₂)₃NR]TiCl₂ (4a,b) and two equiv of ClSiMe₃. An X-ray study of 4a (P2₁/n, a=9.771(1) Å, b=14.189(1) Å, c=21.081(2) Å, β=96.27(1)°, V=2905.2(5) ų, Z=4, T=25°C, R=0.0701, R_w=0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN₂-plane. Compounds 4a,b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH₂)₃NR]TiMe₂ (5a,b). An X-ray study of 5b (P2₁2₁2₁, a=8.0955(10) Å, b=15.288(4) Å, c=16.909(3) Å, V=2092.8(7) ų, Z=4, T=23°C, R=0.0759, R_w=0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium–methyl bond lengths of 2.100(9) Å and 2.077(9) Å. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst·h were obtained in neat 1-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C₆F₅)₃ catalyze the living aspecific polymerization 1-hexene. Polydispersities (M_w/M_n) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph₃C}⁺[B(C₆F₅)₄]⁻. A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine.     

Synthesis and characterization of cationic and zwitterionic allyl zirconium complexes derived from trimethylenemethane (TMM) cyclopentadienylzirconium acetamidinates

Protonation of the trimethylenemethane derivatives, Cp*Zr(σ²,π-C₄H₆)[N(R¹)C(Me)N(R²)] (1a: R¹=R²=i-Pr and 1b: R¹=Et, R²=t-Bu) (Cp*=η⁵-C₅Me₅), by [PhNMe₂H][B(C₆F₅)₄] in chlorobenzene at −10 °C provides the cationic methallyl complexes, Cp*Zr(η³-C₄H₇)[N(R¹)C(Me)N(R²)] (2a: R¹=R²=i-Pr and 2b: R¹=Et, R²=t-Bu), which are thermally robust in solution at elevated temperatures as determined by ¹H NMR spectroscopy. Addition of B(C₆F₅)₃ to 1a and 1b provides the zwitterionic allyl complexes, Cp*Zr{η³-CH₂C[CH₂B(C₆F₅)₃]CH₂}[N(R¹)C(Me)N(R²)] (3a: R¹=R²=i-Pr and 3b: R¹=Et, R²=t-Bu). The crystal structures of 2b and 3a have been determined. Neither the cationic complexes 2 or the zwitterionic complexes 3 are active initiators for the Ziegler-Natta polymerization of ethylene and α-olefins.     

Preparation of various enantiomerically pure (benzotriazol-1-yl)- and (benzotriazol-2-yl)-alkan-2-ols

(S)-(−)-(Benzotriazol-1-yl)- and (S)-(−)-(benzotriazol-2-yl)-alkan-2-ols 7a–9a, 7b–9b and their (R)-(+)-acetates 10a–12a and 10b–12b were prepared in high enantiomeric excess via lipase from Pseudomonas fluorescens (Amano AK) catalyzed enantioselective acetylation of racemic alcohols 4a–6a and 4b–6b with vinyl acetate in tert-butyl methyl ether or toluene at 23 °C. The enantioselectivity of this transformation was dependent on the length of the alkyl chain with E-values ranging from 30 to 57. Several benzotriazole substituted ketones 1a–3a and 1b–3b were synthesized from 1H-benzotriazole and corresponding haloketones. These compounds were stereoselectively reduced with Baker’s yeast in water or in organic solvent containing 5% v/v of water at 30 °C to give the (S)-(−)-alcohol. Better stereoselectivity was observed in the kinetic resolution of racemic alcohols 4a–6a and 4b–6b (ee = 69–92% at 44–52% conversion) compared to reduction of corresponding prochiral ketones 1a–3a and 1b–3b with Baker’s yeast (ee = 40–67% at 39–89% conversion). Enhanced enantioselectivities were observed at lower temperatures.     

Biocatalytic asymmetric and enantioconvergent hydrolysis of trisubstituted oxiranes

Asymmetric biohydrolysis of trialkyl oxiranes (±)-1a–3a using the epoxide hydrolase activity of whole bacterial cells proceeded in an enantioconvergent fashion and thus led to the corresponding (R)-configurated vicinal diols 1b–3b in up to 97% enantiomeric excess (e.e.) as the sole product. The mechanism of this enantioconvergence was investigated by ¹⁸O-labelling experiments and it was found that both enantiomers were hydrolysed with opposite regioselectivity.     

Synthesis of E-vinylogous (R)-amino acid derivatives via metal-catalyzed allylic substitutions on enzyme-derived substrates

Oxynitrilase-derived allylic (R)-cyanohydrin carbonates 3 and allylic (R)-α-hydroxy ester carbonates 6 were examined as substrates for a palladium(0)-catalyzed allylic azidation reaction. The enantioselectivities and cis/trans diastereoselectivities of the concomitant 1,3-chirality transposition step were studied. The cyano carbonates 3a–c were found to be unimpressive substrates producing γ-azido-α,β-unsaturated nitriles 4a–c with cis/trans ratios that approached unity and gave enantiomeric excesses that ranged from 57% to 85%. In contrast, ester carbonates 6a and b were excellent substrates for the reaction exclusively affording trans substitution products 7a and b in identical enantiomeric excesses of 95% ee.     

New cyclic aminals derived from rac-trans-1,2-diaminocyclohexane: synthesis and crystal structure of racemic 1,8,10,12-tetraazatetracyclo[8.3.1.1.8,1202,7] pentadecane and a route to its enantiomerically pure (R,R) and (S,S) isomers

New enantiomerically pure macrocyclic aminals (2R,7R)- and (2S,7S)-1,8,10,12-tetraazatetracyclo[8.3.1.1.^8,120^2,7]pentadecane (4a and 4b) were obtained by a three component reaction between their respective pure enantiomer of trans-1,2-diaminocyclohexane, ammonia, and formaldehyde. Additionally, the X-ray structure of the racemic compound 4 and the specific rotations of the racemic and optically pure compounds were determined. To further understand the synthetic utilities of enantiomers 4a and 4b, Mannich-type reactions with 1H-benzotriazole were performed, affording (3aR,7aR)- and (3aS,7aS)-1,1′-{[2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl]bis(methylene)}bis-1H-benzotriazole (9 and 10) and allowing for new possibilities related to the preparation of chiral ligands for asymmetric catalysis.     

Synthesis and crystal structure analysis of 2-(4-fluorobenzyl)-6-phenylimidazo[2,1-b][1,3,4]thiadiazole and its chlorophenyl derivative

Preparations of 2-(4-fluorobenzyl)-6-phenylimidazo[2,1-b][1,3,4]thiadiazole (3a) and its chlorophenyl derivative (3b) are described. Preliminary analysis was done spectroscopically by means of ¹H NMR, ¹³C NMR spectra, mass spectra and elemental analyses. Further the structures were confirmed by X-ray crystal structure analyses. The compound (3a) has crystallized in a triclinic P-1 space group with three independent molecules in the asymmetric unit, while the compound (3b) belongs to P2₁/c space group with one molecule in the asymmetric unit. The molecule (3b) differs from molecule (3a) by the presence of chlorine substituent. Additionally, the imidazo-thiadiazole entity is as usual planar. Intramolecular C–H⋯N hydrogen bonding between the imidazole and the phenyl ring of the molecule can be observed in (3a) & (3b). The molecules of (3a) are linked into two dimensional supramolecular hexagonal hydrogen bonded network sustained by C–H⋯F interaction, while those of (3b) are linked by bifurcated C–H⋯N interactions. Further, the molecular packing of both the compounds is stabilized by π–π stacking interactions between the benzene and imidazo-thiadiazole ring systems.     

Synthesis of novel β-amino alcohols and their application in the catalytic asymmetric sulfoxidation of sulfides

Novel chiral norephedrine-based β-amino alcohol ligands containing a thiophene ring were prepared from norephedrine and substituted furan carbaldehydes (methyl- or ethyl-substituted) and used in combination with VO(acac)₂ for the asymmetric oxidation of aryl methyl sulfides using H₂O₂ as an oxidant. Amino alcohol derived Schiff bases 4,5a–b gave higher enantiomeric excesses than amino alcohol-derived reduced Schiff based ligands 6,7a–b. Of these chiral ligands, (1S,2R)-5b and (1S,2R)-7b gave high yields (90%) with moderate to high enantioselectivities (78%, 96% ee, respectively). The oxidation of other aryl methyl sulfides with (1S,2R)-5b and (1S,2R)-7b as ligands afforded the corresponding sulfoxides in 60–89% yields and with 92–99% ee.     

Ratiometric fluorescence sensing of phenylalanine derivatives by synthetic macrocyclic receptors

The supramolecular analytical behavior of eight pseudopeptidic fluorescent receptors (1a–c, 2a–c, 3, 4) has been studied. The receptors are either macrocyclic or open chain derivatives based on the naphthalene chromophore. The ability of 1–4 for the molecular recognition of amino acids (as Z-protected derivatives) has been evaluated in dichloromethane. The signal observed corresponds to a fluorescence emission of turn-on type. The preferential binding of all the receptors for phenylalanine (Phe) over aliphatic amino acids (Ala, Val) by a factor of 3–4 has been found. Among the family of studied fluorescent molecules, two macrocyclic receptors (1a and 1b) display high exciplex emissions and great fluorescence changes both at long (fluorescence quenching at 390 nm) and short wavelengths (fluorescence enhancement at 340 nm). This feature makes the macrocycles 1a and 1b potentially practical as fluorescent ratiometric sensors for Phe. As a proof of concept, 1a and 1b have been assayed as analytical tools for the identification of model samples enriched with Phe, mimicking the concentrations found in the pathology phenylketonuria (PKU). This result opens the door to the development of new Phe-sensing sensors based on the exciplex signaling mechanism as a new strategy for the analysis of aminoacidemias.     

Trichloro- and methyldichlorogermyl monochelates and dibromo- and dichlorogermyl bischelates derived from N,N-disubstituted amides of 2-hydroxycarboxylic acids

The reactions of GeCl₄, GeBr₄, and MeGeCl₃ with O-trimethylsilyl derivatives of N,N-disubstituted amides of 2-hydroxycarboxylic acids afforded pentacoordinate and hexacoordinate neutral (O,O)-mono- and (O,O)-bischelates. The reactions of glycolic acid derivatives with GeX₄ produced bischelates X₂Ge[OCH₂C(O)NR²R³]₂ 7a,c,d (X = Cl, R² = R³ = Me (a), (CH₂)₅ (c), (CH₂CH₂)₂O (d)) and 8a (X = Br). By contrast, the reactions of lactic and mandelic acid derivatives with GeCl₄ and MeGeCl₃ gave monochelates Cl₃Ge[OCH(R¹)C(O)NR²R³] (S)-9a–c (R¹ = Me) and Cl₂MeGe[OCH(R¹)C(O)NR²R³] 10a (R¹ = H), (S)-11a,b (R¹ = Me), and (S)-12a (R¹ = Ph) (R²R³ = (CH₂)₄ (b)), respectively. According to the X-ray diffraction data, the Ge atom in bischelates 7c,d and 8a has a coordination number 6, and its coordination polyhedron can be described as a slightly distorted octahedron. In monochelates (S)-9a-c, 10a, (S)-11a,b, and (S)-12a, the Ge atom has a coordination number 5, and its coordination polyhedron can be described as a trigonal bipyramid with two halogen atoms or one halogen atom and one ethereal oxygen atom in equatorial positions and the halogen atom and the amide oxygen atom in the axial positions. The bonds in the axial positions are somewhat longer than the corresponding bonds in tetracoordinate Ge compounds.     

Synthesis and characterization of chalcogen (S and Se) derivatives of 4-chloro- and 4-methoxy-N,N-diisopropylpyridine-2-carboxamide: X-ray structure of 4-methoxy-3-(sulfanylmethyl)- and 4-chloro-3-(selenenylbenzyl)-N,N-diisopropylpyridine-2-carboxamide

Synthesis of chalcogen (S and Se) derivatives of 4-chloro- and 4-methoxy-N,N-diisopropylpyridine-2-carboxamide (1a and 1b respectively) has been reported. 1a and 1b were lithiated with 2 equiv. of n-BuLi or LDA at ?78 °C. Addition of elemental sulfur or selenium to the carbanion led to the formation of corresponding thiolate or selenolate anions respectively. The selenolate anions were aerial oxidized to afford the corresponding diselenides. The thiolate/selenolate anions were quenched with a variety of electrophiles to give unsymmetrical thio/selenoalkanes in moderate to good yields. Reductive cleavage of Se–Se bond has also been studied. The synthesized compounds were characterized by elemental analysis, NMR (¹H, ¹³C and ⁷⁷Se), FT-IR and mass spectral techniques. Crystal structures of two compounds, 6b and 7a, were determined by single crystal X-ray crystallography. Their crystal structure exhibits 1,4-type S?OCH₃ and Se?Cl intramolecular secondary interactions respectively. The relative thermal stability of 3a, 3b and 4a has also been established by thermogravimetric analysis.     

Advanced procedure for the enzymatic ring opening of unsaturated alicyclic β-lactams

Enantiopure β-amino acids 1a–4a and β-lactams 1b–4b were prepared simultaneously through the lipolase-catalysed enantioselective ring opening of unsaturated racemic β-lactams (±)-1-(±)-4. High enantioselectivities (E>200) were observed when the reactions were performed with 1 equiv of water in iPr₂O at 70 °C. The resolved (1R,2S)-amino acids (yield⩾45%) and (1S,5R)-, (1S,6R)- and (1S,8R)-lactams (yield⩾47%) could be easily separated. The ring opening of lactam enantiomers 1b–4b with 18% HCl afforded the corresponding β-amino acid hydrochlorides 1c·HCl–4c·HCl (ee >95%).     

New cyclometalated palladium(II) complexes with iminophosphines: Crystal structures of [Pd(C^N)(o-Ph2PC6H4–CH=NR)][PF6] (C^N=azobenzene,R=Et; C^N=2-phenylpyridine,R=Me)

The synthesis of new cyclometalated compounds of palladium(II) with the mixed-donor bidentate ligands o-Ph₂PC₆H₄–CH=NR is described. Two series of complexes [Pd(C^N)(o-Ph₂PC₆H₄–CH=NR)][PF₆] have been prepared using either azobenzene or 2-phenylpyridine as cyclometalated ligands [C^N=azobenzene (azb); R=Me (1a), Et (2a), ⁿPr (3a), ⁱPr (4a), ^tBu (5a), Ph (6a), NH–Me (7a); C^N=2-phenylpyridine (phpy); R=Me (1b), Et (2b), ⁿPr (3b), ⁱPr (4b), ^tBu (5b), Ph (6b), NH–Me (7b)]. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, FAB, ¹H and ³¹P NMR). The molecular structures of compounds 2a (monoclinic, P 2₁/n) and 1b (monoclinic, C 2/c) have been determined by a single-crystal diffraction study. In both cases this technique revealed the relative trans configuration between the phosphorus atom and the nitrogen atom of the ortho-metalated ligand.     

Synthesis,structure, and property of a triruthenium cluster having a μ-alkyl ligand: Transformation of a μ3(⊥)-alkyne ligand into a μ-alkyl ligand via a μ3-vinylidene complex

A triruthenium μ-alkyl complex, (Cp¹Ru)₃(μ-η²-HCHCH₂R)(μ-CO)₂(μ₃- CO) (2a, R = Ph; 2b, R = ^tBu, Cp¹ = η⁵-C₅Me₅), which contains a two-electron and three-center interaction among Ru, C, and H atoms, has been synthesized by the reaction of a perpendicularly coordinated 1-alkyne complex, {Cp¹Ru(μ-H)}₃(μ₃-η²:η²(⊥)-RCCH) (1a; R = Ph, 1b; R = ^tBu), with carbon monoxide. A diffraction study for 2b clearly represented the bridging neohexyl group on one Ru–Ru edge. This μ-alkyl group exhibited dynamic behavior resulting in site-exchange of the α-hydrogen atoms between the terminal and bridging positions, which was synchronized with the migration of the μ-alkyl groups between the two ruthenium atoms. The agostic C–H bond was readily cleaved upon pyrolysis. Whereas the μ-phenethylidene intermediate resulting from the σ-C–H bond cleavage has never been observed, a μ₃-phenethylidyne complex, {Cp¹Ru(μ-CO)}₃(μ₃-CCH₂Ph) (7a), and a μ₃-methylidyne complex, {Cp¹Ru(μ-CO)}₃(μ₃-CH) (8), were obtained by the successive C–H/C–H and C–H/C–C bond cleavages at the μ-alkyl moiety, respectively.     

Novel thiosemicarbazone derivatives containing benzimidazole moiety: Green synthesis and anti-malarial activity

A series of (E)-2-[5-chloro-1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (7a–7t) and (E)-2-[1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (8a–8t) were prepared via the synthesis of 1-(substituted-1H-benzimidazol-2-yl) ethanol (3a–3b) which was synthesized by the condensation of substituted o-phenylenediamine (2a–2b) with dl-lactic acid (1) followed by oxidation with sodium hypochlorite in mild acidic condition to form the corresponding ketones 4a–4b. Final compounds were formed by condensation of 4a–4b with different thiosemicarbazides 6a–6t. A total of 40 compounds were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, Mass spectral technique and elemental analysis, in addition they were evaluated for anti-malarial properties. Among the compounds tested 7o, 7p, 7q, 7r, 7s, 8e and 8h exhibited good antimalarial activity in vitro.