Synthesis and structure of halogen derivatives of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-Me2S-7,8-C2B9H11]

Halogenation of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-SMe₂-7,8-C₂B₉H₁₁] with N-chlorosuccinimide, bromine and iodine gave the expected corresponding halogen derivatives [9-SMe₂-11-X-7,8-C₂B₉H₁₀], where X = Cl (1), Br (2), I (3). In the bromination reaction, [9-SMe₂-6-Br-7,8-C₂B₉H₁₀] (4) was isolated as a minor product being the first example of substitution at a “lower” belt of the 7,8-dicarba-nido-undecaborate cage. The use of excess of bromine resulted in dibromo derivative [9-SMe₂-6,11-Br₂-7,8-C₂B₉H₉] (5). Structures of the compounds prepared were determined using ¹¹B-¹¹B COSY NMR spectroscopy (for all halogen derivatives) and single crystal X-ray diffraction (for compounds 2, 3, and 5).     

PdCl2-induzierte umlagerung substituierter cis,trans-cyclodeca-1,5-diene

Like the unsubstituted ten-membered ring cis,trans-cyclodeca-1,5-dienes, which are substituted in the 7-, 8- or 9-position, can also be inserted into PdCl₂-complexes of the corresponding substituted cis-1,2-divinylcyclohexanes.Mono- or dimethylsubstitution in the 1-, 2-, 6- or 3,4-position makes this induced Cope-rearrangement impossible or more difficult.     

Dioxamethylene intramolecular bridging of p-tert-butylcalix[8]arene

The first examples of dioxamethylene bridged calix[8]arenes 2-6 have been obtained by Cs₂CO₃-promoted direct O-alkylation of p-tert-butylcalix[8]arene with BrCH₂Cl. Assignment of the 1,2-, 1,2:3,4-, 1,2:3,4:6,7-, 1,4:2,3:5,6:7,8-, and 1,2:3,4:5,6:7,8-bridging pattern of 2-6, respectively, was mainly based on chemical shift of OH groups and chemical correlations. Dynamic ¹H NMR studies and MM3 calculations indicated that in these compounds the dioxocine subunit adopts a boat-chair conformation.     

Darstellung von PdCl2-komplexen substituierter cis,cis-cycloocta-1,5-diene aussachtringen und den entsprechenden substituierten cis-1,2-divinylcyclobutanen. cis,trans-zuordnung 3,4-,3,7- und 3,8-disubstituierter cis,cis-cycloocta-1,5-diene

cis-1,2-Divinylcyclobutanes are transformed with dibenzonitrilepalladium(II) chloride into the corresponding cis,cis-cycloocta-1,5-diene-PdCl₂ complexes. When e.g. the 3-methyl-cis,cis-cycloocta-1,5-diene-PdCl₂ complex is prepared using trans- or cis-3-methyl-cis-1,2-divinylcyclobutane or the corresponding eight-membered ring. two PdCl₂ complexes with the methyl group in the equatorial or axial position are formed in different percentages. With the aid of ¹H NMR spectroscopy the cis- or trans-configurations of 3,4-, 3,7- or 3,8-disubstituted cis,cis-cycloocta-1,5-dienes can be determined unambiguously in PdCl₂ complexes.     

Benzannelated [9] and [13] annulenes: Formation,structural properties and the effect of benzannelation on the aromaticity of the (4n+2) π anionic sy

The synthesis of benzannelated [9] and [13] annulenenes is described, 1,2:3,4-dibenzocyclononatetraene 3 and its diphenyl derivative 10 show upon deprotonation the initial formation of a non-planar partially delocalized anions 4 and 11 respectively, which undergo into the planar aromatic-diatropic dibenzocyclononatetraenyl anions 4a and 12. The immediate formation of the aromatic 1,2:5,6 - dibenzocyclononatetraenyl anion 14 upon deprotonation of 1,2:5,6 - dibenzocyclononatetraene 13 precludes peri H-H repulsions in the aromaticity development of the dibenzocyclononatetraenyl anions. The deprotonation of tetrabenzo[13]annulene 15 afforded anion 17, which shows reduced diatropic character as compared with non-benzannelated[13] annulenyl anion. The spatial arrangement of 17 is discussed.     

Synthesis and characterization of three nickel(ii) carborane complexes containing nido- or closo-carborane diphosphine ligand

Three nickel(II) carborane complexes, [Ni₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] (1), [Ni{7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀}{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (2) and [NiBr₂{1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀}] · CH₂Cl₂ (3), have been synthesized by the reactions of 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane with NiCl₂ · 6H₂O or NiBr₂ · 6H₂O in ethanol under different conditions, respectively. For complex 1, it could also be obtained under the solvothermal condition. All the three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal analysis shows that the molecular symmetry of complex 1 is centrosymmetric, containing two same structure units - Ni(7,8-(PPh₂)₂-7,8-C₂B₉H₁₀) linked by two bridged-Cl atoms. The central square plane formed by the [Ni₂Cl₂] unit is almost parallel to the two side NiPP planes. For complex 2, the coordination environment of the Ni atom is a seriously distorted square-planar, in which two positions come from the chelating diphosphine ligand [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻ degraded from the closo species, while the other two are occupied by an unsymmetrical chelating phosphine oxide ligand [7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀]⁻. As for complex 3, the geometry at the Ni atom is a slightly distorted square-planar. The closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ was coordinated bidentately to the metal ion through the two phosphorus atoms, and the two Br atoms are at cis position which can fulfill the four coordination mode of the metal.     

Convenient construction of a variety of glycosidic linkages using a universal glucosyl donor

This letter deals with the concept of constructing four types (cis-α, trans-α, cis-β, and trans-β) of glycosidic linkages using a universal glucosyl donor. The selectively protected universal glucosyl donor 8 was synthesized in 36% yield from d-glucose (eight steps). The donor 8 undergoes glycosidation with a primary carbohydrate alcohol 7 to give disaccharide 9 having a 1,2-cis-α-glycosidic linkage in 90% yield. The construction of the corresponding 1,2-trans-α-glycosidic linkage was performed in 68% yield (three steps) from 9. A similar glycosidation of the 2-O-(N-phenylcarbamoyl)-glucosyl donor 6 derived from 8 with 7 gave disaccharide 11 having a 1,2-trans-β-glycosidic linkage in 75% yield. The construction of the corresponding 1,2-cis-β-linkage was performed in 53% yield (three steps) from 11.     

Preparation of chiral trans-5-substituted-acenaphthene-1,2-diols by baker’s yeast-mediated reduction of 5-substituted-acenaphthylene-1,2-diones

A series of trans-5-substituted-acenaphthene-1,2-diols were obtained in 21–72% yield with 97–100% ee by baker’s yeast-mediated reduction of the corresponding acenaphthylene-1,2-diones, in the presence of DMSO as a co-solvent and under vigorous agitation. The absolute configuration of (?)-trans-5-methoxy-acenaphthene-1,2-diol trans-3b and (?)-trans-5-bromo-acenaphthene-1,2-diol trans-3c was assigned as (S,S) and (?)-trans-5-thiomorpholin-acenaphthene-1,2-diol trans-3d was established as (R,R) by exciton-coupled circular dichroism.     

Die stereoisomeren bicyclo[4.2.0]octan-cis-Diole-(7,8)

The stereochemical assignment of the bicyclo[4.2.0]octane-cis-7,8-diols is reinvestigated. It is shown that the cis-diols prepared by different routes are indeed stereoisomers, the lower melting being the exo-isomer (1), the higher melting the endo-isomer (2). The synthesis of the previously unknown trans-fused bicyclo[4.2.0]octane-cis-7,8-diol (3) via photosensitized cycloaddition of vinylene carbonate to cyclohexene is described.     

PhP-PPh group bound to 1,8-positions of naphthalene: Preparation of cis isomer and synthesis of binuclear complex

A thermodynamically less stable cis isomer of 1,2-diphosphacycle was prepared from the corresponding trans isomer. Diphosphine, in which a PhP-PPh bond bridges the 1,8-positions of naphthalene, 1,2-diphenyl-1,2-dihydronaphtho[1,8-cd][1,2]diphosphole (1), was first prepared according to a previously reported method, and the trans isomer of 1 was irradiated in tetrahydrofuran with UV-vis light to reach equilibrium with cis-1 in a trans:cis ratio of 1:2. When a similar photochemical conversion was carried out using a saturated hexane solution of trans-1, cis-1 was precipitated in a good yield of 94%. The configuration of cis-1 was confirmed by X-ray analysis. Both cis- and trans-1 diphosphine ligands were used for the preparation of binuclear gold complexes. The crystal structure of (μ-cis-1)-[AuCl]₂ demonstrated that the two lone pairs of cis-1 are suitably directed for arrangement of the two gold centers in close proximity to each other. The two independent (μ-cis-1)-[AuCl]₂ molecules in the crystal were found to form a dimer through the multiple intermolecular interaction among the gold centers.     

Structural analysis of regular copolymers of Butadiene and methylene with repeat unit [But-(CH2)n-But] by the use of model compounds—III. An analysis of the factors which influence the ratio of cis and trans 1,4 addition

In previous papers the 1,2 to total 1,4 ratios in copolymers of butadiene of repeat unit-[But-But-R]¹, where R is an alkyl ligand, have been determined by preparing model compounds HR-But-But-RH under identical conditions. Use of capillary column GLC enables the cis and trans isomers to be separated and the effect of varying experimental parameters on the cis/trans ratio is examined. This ratio is shown to be more sensitive to reaction temperature than the 1,2 to total 1,4 ratios previously studied. Results indicate that when R = (CH₂)_n the cis/trans ratio is independent of n for values of n > 1.     

Stereochemical studies—XVII: Cyclic aminoalcohols and related compounds—IX synthesis and NMR study of stereoisomeric cis- and trans-tetramethylene- and pentamethylene-1,3-oxazine-2-ones

Isomeric tetramethylene- and pentamethylene-1,3-oxazine-2-ones (9–12 and13–16) have been synthesized, derived from cis- and trans-2-aminomethylcyclohexanol (1,2), cis- and trans-2-hydroxymethylcyclohexylamine (3,4) and from the corresponding cycloheptane analogues (5–8), respectively. The stereospecific synthesis of the aminoalcohols5–8 is described. A comparative NMR analysis of13–16 and the tetramethylene analogues (9–12) is given.     

Reactivity of a functionalized trisamido ligand with Zr(NMe2)4 and GaMe3

NMR study of the reactivity of multifunctional ligand cis,cis-C₆H₉(NHCH₂C₆H₄-o-PPh₂)₃ (1) with GaMe₃ and Zr(NMe₂)₄ was carried out, yielding [cis,cis-(κ^N-NHCH₂C₆H₄-o-PPh₂)(κ^N-NCH₂C₆H₄-o-PPh₂)₂C₆H₉]GaMe (2) and [cis,cis-(NCH₂C₆H₄-o-PPh₂)₃C₆H₉]Ga₂Me₃ (3), and [cis,cis-(NCH₂C₆H₄-o-PPh₂)₃C₆H₉]Zr(NMe₂) (4), respectively. The spectral properties of 2 and 3 are very similar to that observed for the equivalent aluminum species already reported, but form at a much slower rate which allows for the observation of a GaMe₃⋅1 adduct. Species 4 undergoes coordination/displacement of one of the phosphine arms, which was observed using both NMR spectroscopy and DFT analyses.     

Synthesis and NMR characterization of cis and trans decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene. Solid state structure of the trans stereoisomer. Modelling studies

The reduction with Vitride^® of the cis and trans isomers of octahydro-2a,4a,6a,8a-tetraazacyclopenten[fg]acenaphthylene 1,2-diones (5 and 6) and octahydro-2a,4a,6a,8a-tetraazacyclopenten[fg]acenaphthylene 3,4-diones (7 and 8) led to the cis9 and the so far unknown trans10 isomers of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene. The stereochemistry of 9 and 10 was determined by comparison of the NMR coupling constants of the proton signals of the ethinic bridge. The results were confirmed by the solid state structure of the trans isomer (10) determined by single crystal X-ray diffraction. Given that the trans bis-aminal species 2 and 4 can undergo rearrangement, i.e. stereoisomerization into the corresponding cis ones (1 and 3, respectively), the conformational behaviour of species 1-4 was investigated by means of both molecular mechanics (MM) and quantum chemical (QC) approaches. The theoretical study was completed by including diamides 5-8 and the final products 9 and 10.     

Reactions of dispiro[2.0.2.2]oct-7-ene. Electrophilic and free radical additions

Dispiro[2.0.2.2]oct-7-ene 1 was synthesized by debrominatioa of cis- and trans-7,8-dibromodispiro[2.0.2.2]octane 3a with LAH and by dechlorination of cis- and trans-7,8-dichlorodispiro[2.0.2.2]octane 3b with magnesium. Stepwise electrophilic additions to 1 of HBr, HI, Br₂ and Cl₂ were studied. The major products (and yields) from these reactions were: 7-bromodispiro[2.0.2.2]octane 2a (43%), 4-iodo-4,5-ethanospiro[2,3]hexane 4b (ca. 50%); trans-3a (40%); and cis-3b (20%). Free-radical addition of hydrogen bromide to 1 gave an 80% yield of 7-bromodispiro[2.0.2.2]octane 2a. At ?10°, hydroboration-oxidation of 1 was found to give mainly 7-hydroxydispiro[2.0.2.2]octane 2a in ca. 90% yield; at 25°, near equal amounts of 2c and 4-(2-hydroxyethyl) spiro[2.3]hex-4-ene 14 were obtained.     

Biphenylenes-xxxi: Condensation of benzocyclobutene-1,2-dione with aliphatic and heterocyclic 1,2-diamines and the synthesis of cis-2-cyano-3-(2'-cyanovinyl)-1,4-diaz

As possible routes to 1,4-diazabiphenylene and its 2,3-disubstituted derivatives we have studied the condensation of benzocyclobutene-1,2-dione (BBD) with various 1,2-diamines. Instead of giving the 1,4-diazabiphenylene ring system, BBD reacted with ethylenediamine, diaminomaleonitrile, 4,5-diaminopyrimidine, 2-aminopyridine, also 2,3- and 3,4-diaminopyridine to give, respectively, 2-o-carboxyphenylimidazolidinium acetate 4, 3,4-dicyano-2,5-dihydro[2,5]benzodiazocine-1,6-dione 10, 4-amino-5a,9b-dihydro-5-,9b-dihydroxybenzo [3',4']cyclobuta[1',2'-4,5]imidazo[1,2-c]pyrimidine 14, 5a,9b-dihydro-5a,9b-dihydroxybenzo[3',4']cyclobuta[1',2'-4,5] imidazo[1,2-a]pyridine 17, the 4-amino derivative 16 of the latter, and the zwitter ion 18 of 4-amino-3(2-carboxy-benzylideneamino) However, BBD reacted with 4,5-diaminobenzotriazole to give the expected 1,2,3,6,11-penta-aza-1-H-indeno [4,5-b]biphenylene 20, which, on amination followed by oxidation, gave a very low yield of cis-2-cyano-3-(2'-cyanovinyl)-1,4-diazabiphenylene 3. In model experiments, 7,8-diphenylfurazano [3,4-f]quinox-aline 28 was reduced to 2,3-diamino-5,6-diphenyl quinoxaline 29, which on oxidation, gave a mixture of cis- and trans-2-cyano-3-(2'-cyanovinyl)5,6-diphenylpyrazine, 30 and 31. The pentacyclic compounds, 1,3,6,II-tetra-aza-2-oxa-2H-indeno [4,5-b]biphenylene 23 and 1,3,5,10-tetra-aza-1-H-indeno[5,6-b] biphenylene 25, were formed from BBD and the appropriate 1,2-diamines but the 5-membered heterocyclic rings could not be cleaved by reduction and hydrolysis respectively) to give tetracyclic diamines which might have undergone oxidation to give derivatives of 1,4-diazabiphenylene. Compounds 14, 16, 20, 23, 25 and 28 are derivatives of new heterocyclic systems.     

Cyclohexyl[trans-1,2-bis(1-indenyl)]zirkonium(IV)dichlorid: Ein chiraler polymerisationskatalysator mit stereochemisch starrer Brücke

Chiral trans-1,2-dimesylcyclohexane (1) reacts with indenylsodium to give trans-1,2-diindenylcyclohexane (2). This ligand precursor was used to prepare a mixture of diastereomeric cyclohexyl-[trans-1,2-bis(1-indenyl)]zirconium(IV) dichlorides (3). In contrast to ethylenebis(1-indenyl) zirconium(IV) dichloride (4), compound 3 catalyses the polymerization of propene with high stereoselectivity, even at polymerization temperatures above 50°C.     

Synthesis and crystal structure of four Pd(II) complexes containing nido or closo carborane diphosphine ligands

Three Pd(II) complexes [Pd₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 0.25CH₂Cl₂ (1), [Pd{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 4CHCl₃ (2) and [PdCl₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (3) have been synthesized by the reactions of 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ with PdCl₂ in acetonitrile, cyanophenyl and dichloromethane, respectively. A fourth complex, [PdI₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (4), was obtained by a ligand exchange reaction through the substitution of the Cl⁻ of complex 3 with I⁻. All four complexes have been characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal X-ray determination showed that the carborane cage, nido for 1, 2 and closo for 3, 4, was coordinated bidentately to the Pd atom through the two P atoms, and the geometry at the Pd atom was square-planar in all the complexes.     

Silicon-carbon unsaturated compounds. 73. Photolysis of cis- and trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane in the presence of tert-butyl alcohol and acetone

Irradiation of cis-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1a) in the presence of tert-butyl alcohol in hexane with a low-pressure mercury lamp bearing a Vycor filter proceeded with high stereospecificity to give cis-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2a), in 33% isolated yield, together with a 15% yield of 1-[(tert-butoxy)methylphenylsilyl]-4-(methylphenylsilyl)butane (3). The photolysis of trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1b) with tert-butyl alcohol under the same conditions gave stereospecifically trans-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2b) in 41% isolated yield, along with a 12% yield of 3. Similar photolysis of 1a and 1b with tert-butyl alcohol-d₁ produced 2a and 2b, respectively, in addition to 1-[(tert-butoxy)(monodeuteriomethyl)(phenyl)silyl]-4-(methylphenylsilyl)butane. When 1a and 1b were photolyzed with acetone in a hexane solution, cis- and trans-2,3-benzo-1-isopropoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (4a and 4b) were obtained in 25% and 23% isolated yield. In both photolyses, 1-(hydroxymethylphenylsilyl)-4-(methylphenylsilyl)butane (5) was also isolated in 4% and 5% yield, respectively. The photolysis of 1a with acetone-d₆ under the same conditions gave 4a-d₆ and 5-d₁ in 18% and 4% yields.     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.