Structural control in palladium(II)-catalyzed enantioselective allylic alkylation by new chiral phosphine-phosphite and pyridine-phosphite ligands

The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η³-C₃H₅)(L-L′)]CF₃SO₃ (L–L′=1–(S)-5) and [Pd(η³-PhCHCHCHPh)(L–L′)]CF₃SO₃ (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η³-C₃H₅)Cl]₂ and [Pd(η³-PhCHCHCHPh)Cl]₂, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by ¹H, ³¹P{¹H}, ¹³C{¹H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η³-C₃H₅)((S)-4)]CF₃SO₃, 11, and [Pd(η³-C₃H₅)((S)-5)]CF₃SO₃, 12, since the corresponding species [Pd(η³-PhCHCHCHPh)((S)-4)]CF₃SO₃, 13, and [Pd(η³-PhCHCHCHPh)((S)-5)]CF₃SO₃, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η³-C₃H₅)((S)-2)]CF₃SO₃ afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η³-C₃H₅)((S)-3)]CF₃SO₃. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process.     

Darstellung und eigenschaften von 124,2,4,6-thiatriazin-1-oxiden. zur struktur der hydrolyseprodukte von 1-arensulfonyl-imino-1λ4,2,4,6-thiatriazinen

Synthesis and structure of 4-phenoxy-H[1λ⁴,2,4,6]thiatriazino[4,3a]benzimidazole-2-oxide 5, 3-amino-4H[1λ⁴,2,4,6]thiatriazino[2,3-a]benzimidazole-1-oxide 6 and 3-amino-5-dimethylamino-2-tosyl-1λ⁴, 2,4,6-thiatriazine-1-oxide 7, obtained by hydrolysis of the corresponding arenesulfonyl imino compounds are discussed. The molecular and crystal structure of N-benzoyl-? tosyl-guanidine is presented.     

Structural controlled pure metallo-triangular assembly through bisterpyridinyl Dibenzo[b,d]thiophene,Dibenzo[b,d]furan and Dibenzo[b,d]carbazole

A novel family of metallocycles was constructed by a one-pot self-assembly of three analogous bis(terpyridine) ligand monomers L1-L3, having different bent angles, with metal ions (Zn²⁺ or Cd²⁺). The dibenzo[b,d]thiophene-containing ligand L3 assembled with the metal ions to form a single trimer, whereas the dibenzo[b,d]furan-containing ligand L2 and dibenzo[b,d]carbazole-containing ligand L1 formed a mixture of trimers and tetramers. Heteroatoms (N, O, S) significantly contributed to the molecular size of the assemblies, owing to the bent angle of the bis-terpyridines ligands.     

New hydrogen-bonded dimeric and polymeric gold(I) complexes of the heterodifunctional ligand Ph2PNHP(O)Ph2

The preparation of several new gold(I) complexes by chloride metathesis of [AuCl(HL)] [HL=Ph₂PNHP(O)Ph₂] with either HL or K[Ph₂P(E)NP(E)Ph₂] (E=S or Se) is described. All compounds were characterised by a combination of ³¹P{¹H}, ¹H and IR spectroscopy, microanalysis and X-ray crystallography. X-ray structural studies reveal that [Au(HL)₂]Cl [monoclinic, space group P2₁/c, a=9.0726(3) Å, b=21.0847(6) Å, c=12.0131(3) Å, β=105.1090(10)°, V=2219 ų, Z=2, final R=3.97] forms a one dimensional polymeric structure in which alternating [Au(HL)₂]⁺ and Cl⁻ ions are linked through intermolecular N–H⋯Cl hydrogen-bonding. In contrast the three-co-ordinate compound [Au{Ph₂P(Se)NP(Se)Ph₂-Se,Se′}(HL)] [monoclinic, space group P2₁/a, a=21.6752(5) Å, b=9.1200(10) Å, c=24.0742(7) Å, β=106.080(2)°, V=4573 ų, Z=4, final R=8.94] forms hydrogen-bonded dimer pairs analogous to that previously observed in non-complexed HL. The X-ray crystal structure of the gold(I) precursor [AuCl(HL)] has also been determined: monoclinic, space group P2₁/c, a=10.217(8) Å, b=23.256(5) Å, c=20.086(5) Å, β=101.15(4)°, V=4683 ų, Z=8, final R=5.2. The X-ray crystal structure reveals intermolecular N–H⋯OP hydrogen-bonding between adjacent [AuCl(HL)] molecules forming infinite chains.     

Syntheses and properties of NCN-bridged tri- and tetranuclear complexes of cobalt and rhodium

The reaction of [Cp¹CoI₂]₂ (1b) with 2 equiv of NaNCNH affords the 16-membered macrocyclic NCNH-bridged tetracobalt(III) complex [Cp¹CoI(μ₂-NCNH-N,N′)]₄ (2b), while that with 2 equiv of Na₂NCN yields the C₃-elongated cubane-like NCN-bridged tetracobalt(III) complex [Cp¹Co(μ₃-NCN-N,N,N′)₃(CoCp¹)₃(μ₃-NCN-N,N,N)] (4b). Treatment of [Cp¹RhCl₂]₂ (1c) with 2 equiv of NaNCNH gives the C₃-elongated cubane-like tetrarhodium(III) complex [Cp¹Rh(μ₃-NCN-N,N,N′)₃(RhCp¹)₃(μ₃-NCN-N,N,N)] (4c) via the macrocyclic complex [Cp¹RhCl(μ₂-NCNH-N,N′)]₄ (2c). On the other hand, the reaction of [Cp¹CoCl]₂ (7) with Na₂NCN affords the anionic bis(NCN)-capped tricobalt(II) complex Na[(Cp¹Co)₃(μ₃-NCN-N,N,N)₂] (6). The molecular structures of complexes 2b · CH₂Cl₂ and 4c · 2C₆H₆ have been confirmed by X-ray analyses. The electrochemical properties of these types of NCN-bridged group 9 metal complexes have also been examined.     

Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

The redox reaction of bis(2-benzamidophenyl) disulfide (H₂L-LH₂) with [Pd(PPh₃)₄] in a 1:1 ratio gave mononuclear and dinuclear palladium(II) complexes with 2-benzamidobenzenethiolate (H₂L⁻), [Pd(H₂L-S)₂(PPh₃)₂] (1) and [Pd₂(H₂L-S)₂ (μ-H₂L-S)₂(PPh₃)₂] (2). A similar reaction with [Pt(PPh₃)₄] produced only the corresponding mononuclear platinum(II) complex, [Pt(H₂L-S)₂(PPh₃)₂] (3). Treatment of these complexes with KOH led to the formation of cyclometallated palladium(II) and platinum(II) complexes, [Pd(L-C,N,S)(PPh₃)]⁻ ([4]⁻) and [Pt(L-C,N,S) (PPh₃)]⁻ ([5]⁻). The molecular structures of 2, 3 and [4]⁻ were determined by X-ray crystallography.     

Structures of the tricyclododecenes prepared by the catalytical intramolecular cyclisation of 1,5,9-cyclododecatriene

The internal cyclisation of 1,5,9-cyclododecatriene, induced by a catalytical amount of Cp₂TiCl₂-LAHδ, leads to a mixture of cis, anti, cis-tricyclo[7.3.0.0^2,6]-7-dodecene (1), cis,syn,trans-tricyclo[7.3.0.0^2,6]-7-dodecene (2), trans,syn-tricyelop[7.3.0.0^2,6]-6-dodecene (3) and 5,6,7,8,9,10-hexahydrobenzocyclooctene (4). The structures of the main products were determined from the spectra of a number of derivatives taking into account symmetry properties and configurational flexibility.     

New bicyclic organylboronic esters derived from iminodiacetic acids

The reactions of phenylboronic acid or dinethylthexyboronic ester with iminodiacetic- or N-methyliminodiacetic acids lead to high yield to the air-stable bicyclic esters (N-B)phenyl[iminodiacete-O,N]borane (1), (N-B)phenyl[N-methyliminodiacetate-O,N]borane (2), (N-B)thexy[iminodiacetate[O,N]borane (3) and (N-B)thexyl[N-methyliminodiacetate-O,N]borane (4). These are shown by ¹H, ¹¹B and ¹³C NMR spectroscopy to have rigid bicyclic structures of strong intramolecular N-B coordination.     

Preparations and properties of pseudo-geminal ketones of tris-[2.2.2]- and tetrakis[2.2.2.2]parazylylene

Pseudo-geminal bridged ketones of tris[2.2.2]paraxylylene, 1, and of tetrakis[2.2.2.2]paraxylylene, 2, were prepared and their spectral properties were investigated in comparison with those of dibenzosuberone, 3. The CO stretching band of 1 was observed at abnormally high frequency region (by ca. 50 cm^?1) compared with that of 3, while that of 2 was at a position similar to that of 3. The electronic spectrum of 1 showed that 1 has enormous loss of conjugation due to lack of coplanarity between CO and aromatics. The chemical shift of H⁰, ortho to CO, of 1 also supported this structural characteristic.     

Trimer–dimer equilibrium studies of alkylaluminum alkoxides

The aluminum alkoxides [MeClAlOEt]₃ (1), [Et₂AlOMe]₃ (2), [Me₂AlOEt]₃ (3), and [EtClAlOEt]₃ (4) were investigated by ¹H NMR spectroscopy to study the o-dichlorobenzene solution equilibrium: 2 [R₂AlOR′]₃⇌3 [R₂AlOR′]₂. The complexes are shown to exist primarily as trimers at room temperature, but increasing concentrations of the dimeric form are observed at higher temperatures. Equilibrium constants, ΔH, and ΔS were determined for the trimer–dimer equilibrium. Values of ΔH for the conversion of 2 moles of trimer are 63(4), 78(1), 85.0(8), and 99(6) kJ for 1, 2, 3, and 4, respectively. The corresponding values of ΔS are 142(7), 184(3), 218(2), and 265(17) J/K, respectively. Thermodynamic parameters are compared with those reported for [Me₂AlOPrⁿ]₃ and [Me₂AlOPh]₃. The characterization of [EtClAlOMe]₃ is also reported.     

Synthesis and application of an efficient calix[4]arene-based anion receptor bearing imidazole groups for Cr(VI) anionic species

We synthesized the new calix[4]arene amines bearing two and four imidazole or tert-butylamine moieties (9a,b/10a,b) by the reaction of di- or tetra-tosylated calix[4]arene derivatives (7 and 8, respectively) with 1-(3-aminopropyl)imidazole and/or tert-butylamine, respectively. After the characterization of 9a,b/10a,b their extraction abilities toward Cr(VI) anionic species (CAS) was evaluated and compared by the liquid–liquid extraction method. The extraction results revealed that calix[4]arene amine having four imidazole groups (10a) was an efficient anion receptor for CAS. Moreover, the extraction of CAS by 10a in the presence of other anions such as Cl^?, NO₃^?, and PO₄^3? showed that 10a could be a selective anion receptor for CAS in the presence of those anions.     

Synthesis,characterization and biological activity of Hg(II), Fe(III) complexes with 1,3,4-oxadiazole, 1,2,4-triazole derivatives from L-methionine

Four novel heterocyclic1,3,4-oxadiazole, 1,2,4-triazole derivatives, namely: 5-[1-amino-3-(methylsulfanyl)propyl]-1,3,4-oxadiazole-2(3H)-thione (4), 4-amino-5-[1-amino-3-(methylsulfanyl)propyl]-4H-1,2,4-triazole-3-thiol (5), 1-amino-3-[1-amino-3-(methylsulfanyl)propyl]-1H-1,2,4-triazole-5-thiol (7), and 5-[1-amino-3-(methylsulfanyl)propyl]-1H-1,2,4-triazole-3-thiol (9) have been synthesized from l-methionine and characterized by different spectroscopic techniques (FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and MS). Complex formation with Hg⁺⁺ and Fe⁺⁺⁺ ions were formed from the four heterocyclic 4, 5, 7 and 9. The antimicrobial activities for synthetic intermediates and final four products were assisted using paper disk diffusion method against Gram-negative bacteria: Escherichia coli, Pseudomonas aeroginosae and Gram-positive bacteria: Staphylococus aureus 25923, Staphylococus aureus 43300 and showed variant activity against some of the microorganisms tested.     

Reactions of the 1-halo-7-(2-hydroxyethoxy)cycloheptenes and the 3-halo-4-(2-hydroxyethoxy)bicyclo[3.2.1]oct-2-enes with potassium t-butoxide

Reactions of 1 - bromo - 7 - (2 - hydroxyethoxy)cycloheptene 2 and its chloro analogue 3 with potassium t-butoxide in dimethyl sulphoxide or tetrahydrofuran gave cycloheptatriene and cis - 8,11 - dioxabicyclo[5.4.0]undec - 2 - ene 18 as the major products together with small amounts of the trans-isomer 17,8,11-dioxabicyclo[5.4.0]undec - 1(7) - ene 14, 8,11 - dioxabicyclo[5.4.0] - undec - 1 - ene 19, cyclohept - 2 - enone ethylene ketal 15, cyclohept - 3 - enone ethylene ketal 16, and 1- and 2 - t - butoxycyclohepta - 1,3 - diene 20. Similar reactions of 3 - bromo - and 3 - chloro - 4 - (2 - hydroxyethoxy)bicyclo[3.2.1]oct - 2 - ene 4 and 5 gave 4,7 - dioxatricyclo[7.2.1.0^3,8]dodeca - 2 - ene 26 as the major product together with small amounts of 3,6 - dioxatricyclo[7.2.1.0^2,7]dodeca - 2(7) - ene 27 and bicyclo[3.2.1]oct - 3 - ene - 2 - one ethylene ketal 28. Mechanisms for these transformations are discussed.     

Synthesis of new chiral calix[4]arene diamide derivatives for liquid phase extraction of α-amino acid methylesters

The synthesis of chiral diamide derivatives of calix[4]arene from the reaction of p-tert-butylcalix[4]arene diester 1a and calix[4]arene diester 1b with various amino alcohols were reported. The ¹H and ¹³C NMR, data showed that the compounds synthesized exist in the cone conformation. The extraction study properties of these new compounds 3a,b–4a,b towards some selected α-amino acid methylesters are also reported.     

Emission of 2-phenylethanol from its β-d-glucopyranoside and the biogenesis of these compounds from [H8] l-phenylalanine in rose flowers

The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2′,3′,4′,5′,6′-²H₇]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-²H₈]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2,2′,3′,4′,5′,6′-²H₈]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-²H₈] l-phenylalanine ([²H₈]-1) with a retention of the deuterium atom at α-position of [²H₈]-1.     

Reaction of benzyne with cycloheptatriene preparation and thermolysis of some benzo(C9H10) hydrocarbons

The title reaction gave a 2+2 cycloadduct, 8,9-benzo-cis-bicyclo[5.2.0]nona-2,4,8-triene 7, together with ene product, 7-phenylcycloheptatriene. The structure of 7 was confirmed by catalytic reduction to give 8,9-benzo-cis-bicyclo[5.2.0]non-8-ene, which was also obtained in the reaction of benzyne with cycloheptene, and by reduction of the known 8,9-benzobicyclo[5.2.0]nona-1,8-diene. Other benzo(C₉H₁₀) hydrocarbons which have been synthesised are 7,8-benzobicyclo[4.2.1]nona-2,4,7-triene 5, 2,3-benzobicyclo[6.1.0]nona-2,4,6-triene 28 and 4,5-benzobicyclo[6.1.0]nona-2,4,6-triene 29. The thermolysis of 7, 28, 29 and of 3,4-benzo-exo-endo-tetracyclo[4.3.1.0^3,4.0^7,9]dec-3-en-10-one, 25, is described.     

Synthesis and electrochemical properties of calix[4]arene derivatives containing ferrocene units in the cone and 1,3-alternate conformation

Two novel calix[4]arene receptors containing ferrocene units in cone (L₁) and 1,3-alternate (L₂) conformations have been synthesized from 25,27-dihydroxy-26,28-bis[(3-aminopropyl)oxy]calix[4]arene 4 or 25,26,27,28-tetra[(3-aminopropyl)oxy]calix[4]arene 6 and ferrocenecarboxaldehyde via condensation, respectively. Their structures have been characterized by ¹H, ¹³C, APT, COSY NMR, FTIR, HSMR, and UV–vis spectral data. The electrochemical behavior of L₁ and L₂ has been investigated in the presence of F^?, Cl^?, Br^?, H₂PO₄^?, CH₃COO^? anions. Electrochemical studies show that these receptors electrochemically recognize CH₃COO^?, H₂PO₄^?, and Cl^?, anions. Using an UV–vis study, the selectivity to these anions in DMSO solution was confirmed.     

Preparation and structures of the binuclear vanadium(II) complexes [L3V(μ-Cl)3VL3]BPh4 (L = tetrahydrofuran or 3-methyltetrahydrofuran)

Two compounds of the general formula [L₃V(μ-Cl)₃L₃]BPh₄ [L = tetrahydrofuran (1) or 3-methyltetrahydrofuran (2)] were prepared and investigated via single-crystal X-ray studies. Compound 1, tris(μ-chloro)hexakis(tetrahydrofuran)divanadium(II) tetraphenylborate, crystallizes in space group P2₁/c with unit-cell dimensions: a = 16.636(6) Å, b = 16.771(5) Å, c = 19.158(5) Å, β = 110.71(4)°, V = 5000(6) ų, Z = 4. Compound 2, tris(μ-chloro)hexakis(3-methyltetrahydrofuran)divanadium(II) tetraphenylborate, forms monoclinic crystals (space group Cc) with a = 18.376(5) Å, b = 10.843(3) Å, c = 29.317(6) Å, β = 103.02(2)°, V = 5691(5) ų, Z = 4. Refinement, by least-squares methods using a data to parameter ratio of 6.1 for 1 and 9.1 for 2, converged with an unweighted discrepancy index of 7.46 and 5.31 % for 1 and 2, respectively. The V—V′ distances are: 2.978(3) Å for 1 and 2.976(1) Å for 2. The use of 3-methyltetrahydrofuran as a supporting ligand is discussed since such substituted THF molecules reduce the tendency to disorder in the [V₂(μ-Cl)₃(THF)₆]⁺ cations.     

Dianionic complexes with hexacoordinate silicon(IV) or germanium(IV) and three bidentate ligands of the salicylato(2–) type: Syntheses and structural characterization in the solid state and in solution

Reaction of tetramethoxysilane or tetramethoxygermane with salicylic acid and morpholine (molar ratio 1:3:2) in tetrahydrofuran yielded morpholiniummer-tris[salicylato(2–)-O¹,O³]silicate(mer -5) and morpholiniummer-tris[salicylato(2–)-O¹,O³]germanate (mer-8), respectively. Treatment of tetramethoxysilane with 5-chlorosalicylic acid and piperidine (molar ratio 1:3:2) in tetrahydrofuran afforded piperidinium mer-tris[5-chlorosalicylato(2–)-O¹,O³]silicate–ditetrahydrofuran (mer-6·2THF). Triethylammonium mer-tris[3-methylsalicylato(2–)-O¹,O³]silicate (mer-7) was obtained analogously by reaction of tetramethoxysilane with three molar equivalents of 3-methylsalicylic acid and two molar equivalents of triethylamine in dichloromethane/diethyl ether. The racemic compounds mer-5, mer-6· 2THF,mer-7, and mer-8 were characterized by elemental analyses (C, H, N), single-crystal X-ray diffraction, as well as solid-state (²⁹Si) and solution(¹H, ¹³C, ²⁹Si) NMR studies. The structural characterizationwas complemented by computational studies (HF studies, TZVP level) of thefac- and mer-tris[salicylato(2–)-O¹,O³]silicatedianion. In addition, the behavior of mer-7 in solution was studied by VT ¹HNMR experiments.