Synthesis of dimethyl substituted benzimidazoles containing cyclopropane fused onto five to eight membered [1,2-a]alicyclic rings and influence of methyl group substituents on cytotoxicity of benzimidazolequinones

Upon thermolysis 5,6-dimethyl-N-[(allyl, but-3-enyl, pent-4-enyl and hex-5-enyl-benzimidazol-2-yl)methylene]-(trans)-2,3-diphenylaziridin-1-amines (Eschenmoser hydrazones) form cyclopropane fused onto pyrrolo-, pyrido-, azepino- and azocino[1,2-a]benzimidazoles in 70, 50, 77 and 11% yield, respectively. The latter reaction also gave carbene insertion products. Dimethyl group substituents were found to significantly reduce the cytotoxicity of benzimidazolequinone towards human skin fibroblast cells.     

New developments in the Pd-catalysed cyclisation-coupling reaction of alkene-containing carbonucleophiles with organic halides (and triflates). The first examples of asymmetric catalysis.

The results of our preliminary investigations directed toward asymmetric catalysis of the cyclocarbopalladation of alkenes bearing a proximate nucleophile with organic halides (or triflates) are disclosed. A series of bidentate phosphine ligands were evaluated in intramolecular versions of this reaction using (E)-2-[7-(2-bromophenyl)-hept-4-enyl]-malonic acid dimethyl ester (1) and (Z)-2-[7-(2-trifluoromethanesulfonyloxy-phenyl)-hept-4-enyl]-malonic acid dimethyl ester (9) as model substrates. The highest enantioselective induction was obtained with aryl triflate 9 which produced the corresponding cyclopentylindane as a single diastereomer in 54% chemical yield and 43% ee by using PdCl₂[S-(−)-TolBINAP] as chiral catalyst and K₂CO₃ as base.     

Si-disubstituted diallylsilanes in homolytic thiylation and electrophilic fragmentation reactions

Approaches to Si-disubstituted 1-thia-5-silacyclooctanes based on homolytic addition of hydrogen sulfide to diallylsilanes R₂Si(CH₂CH=CH₂)₂ and on intramolecular cyclization of Si-disubstituted (allyl)(γ-sulfanylpropyl)silanes have been studied. In the former case the reactivity of the silanes decreases in the order R = MeO > F > Me > Ph, whereas in the latter case the reactivity order is slightly different: Me > MeO ≈ F ? Ph. The reactions of diphenyl-and dimethyldiallylsilanes with the complex BF₃·2AcOH occur in a different manner: The former involves rearrangement to form fluoro(2-methylpent-4-enyl)diphenylsilane, while the latter, elimination of the two allyl groups to fluorodimethylsilane and propene.     

Approach to highly functionalized oxazolones by a Pd-catalyzed cyclization of N-alkynyl tert-butyloxycarbamates

A mild and operationally simple approach to highly functionalized oxazolones has been developed, which involves an intramolecular oxypalladation of N-alkynyl tert-butyloxycarbamates, followed by either protonolysis of the alkenyl C-Pd bond to afford 3,5-disubstituted oxazolones or allylation with allyl halides in the presence of Ag₂CO₃ to generate 3,4,5-trisubstituted oxazolones, respectively.     

Reactions of Elemental Phosphorus and Phosphine with Electrophiles in Superbasic Systems: XV. Phosphorylation of Allyl Halides with Elemental Phosphorus

Elemental phosphorus (red or white) reacts with allyl chloride and allyl bromide in a two-phase system aqueous KOH-organic solvent to form tertiary symmetrical and mixed phosphine oxides among which tris(prop-2-enyl)-, bis(prop-2-enyl)[(E)-prop-1-enyl]-, bis(prop-2-enyl)[(Z)-prop-1-enyl]-, (prop-2-enyl)[(E)-prop-1-enyl][(Z)-prop-1-enyl]-, bis[(E)-prop-1-enyl](prop-2-enyl)-, bis[(Z)-prop-1-enyl](prop-2-enyl)-, tris-[(E)-prop-1-enyl]-, and bis[(E)-prop-1-enyl][(Z)-prop-1-enyl]phosphine oxides were identified. The conditions (room temperature, 60% aqueous KOH-dioxane) allowing preparation from white phosphorus and allyl bromide of tris(prop-2-enyl)- and bis(prop-2-enyl)[(E)-prop-1-enyl]phosphine oxides as major products in the total yield of up to 96% were found.     

The use of chloroalkyldichloroarsines in hybrid ligand synthesis. The preparation of but-3-enylbis(3-dimethylarsinopropyl)arsine and 3-dimethylarsinopropylbis(but-3-enyl)arsine,and their reaction with nickel(II) salts to form pentacoordinate complexes. Novel nickel(II)—olefin bonds

Routes have been developed to the hitherto unobtainable arsine-olefin ligands (CH₂CHCH₂CH₂)_nAs(CH₂CH₂CH₂AsMe₂)_3-n (n = 1, tasol, but-3-enylbis(3-dimethylarsinopropyl)arsine; n = 2, dasdol, 3-dimethylarsinopropylbis(but-3-enyl)arsine) by making use of the difference in reactivity between the ClC and AsCl bonds in the precursor Cl(CH₂)_mAsCl₂ (m = 2,3) molecules. Thus, the triarsine obtained by reaction of 2-chloroethyldichloroarsine with the Grignard reagent of 3-chloropropyldimethylarsine yields 2-chloroethylbis(3-dimethylarsinopropyl)arsine, from which tasol is obtainable by subsequent reaction with either the Grignard reagent of vinyl bromide or, preferably, with vinyllithium. Similarly, 3-chloropropyldichloroarsine reacts with the Grignard reagent of 4-chlorobut-1-ene to form 3-chloropropylbis(but-3-enyl)arsine which, on reaction with sodium dimethylarsenide yields dasdol. The tasol ligand reacts with nickel(II) salts to form [NiX(tasol)]⁺ (X = Cl, Br) and [NiI₂(tasol)], the former are trigonal bipyramidal and contain a nickel(II)—olefin bond, and the latter are square pyramidal containing a [NiI₂As₃] coordination sphere. In addition, tasol forms a number of polynuclear complexes with nickel(II). The dasdol ligand acts as a bidentate arsine to form only [NiX(dasdol)₂)]⁺ The formation of novel nickel(II)—olefin bonds in the [NiX(tasol)]⁺ cations is discussed.     

Intramolecular OH···π interactions in alkenols and alkynols

The vibrational overtone spectra of propargyl alcohol (prop-2-yn-1-ol, PA), allyl alcohol (prop-2-en-1-ol, AA), propargyl carbinol (but-3-yn-1-ol, PC) and allyl carbinol (but-3-en-1-ol, AC) were recorded with intracavity laser photoacoustic spectroscopy (ICL-PAS) in the Δv(OH) = 3, 4 and 5 regions for propargyl alcohol and allyl alcohol and in the Δv(OH) = 4 and 5 regions for propargyl carbinol and allyl carbinol. Local mode anharmonic oscillator calculations were performed with explicitly correlated coupled cluster methods to guide spectral assignment. Atoms in molecules (AIM) and non-covalent interactions (NCI) calculations were carried out to analyze the interactions between the OH-group and the π-electrons of the carbon-carbon multiple bonds. We ascertain the effect of the carbon chain length and saturation on the conformation and spectroscopy of the four alcohols in relation to intramolecular hydrogen bonding interactions.     

Unusual transformation of (1<Emphasis Type="Italic">R</Emphasis>,1′<Emphasis Type="Italic">S</Emphasis>,2<Emphasis Type="Italic">S</Emphasis>)-1-(3-diisopropylamino-3-oxopropyl)-2-(1-hydroxyethyl)cyclopropane in the course of the cyclopropylcarbinyl rearrangement

The cyclopropylcarbinyl rearrangement of (1R,1′ S,2S)-1-(3-diisopropylamino-3-oxo-propyl)-2-(1-hydroxyethyl)cyclopropane and the participation of the amide moiety in the intramolecular process smoothly affords the (2′ E,5S)- N,N-diisopropyl-N-[5-(but-2′-enyl)tetra-hydrofuran-2-yridene ] ammonium salt.     

Zur Oxydation von Gemischtligand-Nickel(0)-Komplexen mit organischen Halogeniden

Oxidation of Mixed Ligand Nickel(0) Complexes by Organic Halides The oxidation of (dipy)Ni(PPh₃)₂ by alkyl and aryl iodides or bromides affords the nickel(I) complexes (dipy)Ni(PPh₃)X (X = Br, I). No normal products of oxidative addition are obtained. But in the case of methyl and ethyl halides complexes of the type (dipy)NiR₂ are formed as intermediates. Basing on the identified final products and on the correalation between the reactivity of the organic halides and their polarographic half wave potentials a mechanism of the reaction is proposed. The first step is a charge transfer from nickel(0) to the organic halide. Further synthesis, reactions, and the ESR-spectra of the complexes (dipy)Ni(PPh₃)X and a synthesis of (dipy)Ni(CH₂Ph)₂ are described. Experiments to prepare pure (dipy)Ni(PPh₃)Cl had no success.     

New isothiocyanatotolane liquid crystals with terminal but-3-enyl substitute

Four kinds of new but-3-enyl-based isothiocyanate liquid crystals composed of tolane core and but-3-enyl terminal group (A1–A4) were synthesised via seven step reactions based on 2-(4-bromophenethyl)-1,3-dioxolane, and four n-butyl analogues B1–B4 as comparison structures were also prepared. The mesomorphic properties and physical properties of the compounds were investigated. Single fluorinated compounds A2 and A3 exhibit monotropic nematic phase, and they have lower melting enthalpy and higher clearing points than those of the comparison compounds B2 and B3. The non-fluoro-substituted compound A1 and difluorinated compound A4 exhibit no nematic phase. Replacement of n-butyl chain by but-3-enyl as terminal group is enabled to increase birefringence (Δn ~ 0.394–0.430) and reduce rotational viscosity. These isothiocyanatotolanes with terminal but-3-enyl substitution have potential application for high birefringence mixtures.     

Oxidative addition reactions of dicyclopentadienyltin(II) and of tin(II) bis(acetylacetonate) with organic halides. The preparation of compounds of the type RSn(acac)2X

Oxidative addition reactions of tin(II) bis(acetylacetonate) with organic halides provide a route to new monoorganotin(IV) bis(acetylacetonate) halides. Dicyclopentadienyltin(II) undergoes oxidative addition with methyl iodide, diiodomethane and ethyl bromoacetate, but with allyl bromide, benzyl bromide and triphenylmethyl bromide carbon—carbon coupling reactions and the formation of the corresponding cyclopentadienyltin(II) halide take place. Some of the reactions are accelerated by light. NMR spectroscopic data show that the RSn(acac)₂X compounds have a cis-configuration. The compounds YCH₂Sn(acac)₂X (e.g. Y = I, CHCH₂, COOEt) provide the first examples of diastereo-topic non-equivalence of methylene protons in organotin compounds containing a hexacoordinate chiral tin centre.     

Specific solvent effects on the intramolecular electron transfer reaction in a neutral ferrocene donor polychlorotriphenylmethyl acceptor radical with extended conjugation

The synthesis and the optical, magnetic and electrochemical properties of the ferrocenylbutynene substituted polychlorotriphenylmethyl radical 1 are reported. Radical 1 is prepared in a three step synthetic route starting with a Wittig reaction to yield (E,Z)-{4-[4-(bis(2,3,4,5,6-pentachlorophenyl)methyl)-2,3,5,6-tetra-chlorophenyl]but-3-en-1-ynyl}-ferrocene (1H) which is subsequently deprotonated to yield the corresponding anion K⁺(18-crown-6) [1]^? and finally oxidized to (E)-4-[4-(ferrocenyl)but-3-yn-1-enyl]-2,3,5,6-tetrachlorophenyl-bis(2,3,4,5,6-pentachlorophenyl) methyl radical (1). Radical 1 exhibits a charge-transfer band transition in the near infrared region which is associated with an intramolecular electron transfer from the ferrocene unit (donor) to the radical unit (acceptor) of this dyad molecule; its solvatochromism is studied in detail. The X-ray crystal structure of [K⁺(18-crown-6)](E)-[4-[4-(ferrocenyl)but-3-yn-1-enyl]-2,3,5,6-tetrachlorophenyl-bis(2,3,4,5,6-pentachlorophenyl) methide] [1]^? has been determined. This organic salt forms an interesting one-dimensional coordination polymer by the coordination of the K⁺ cation with chlorine atoms of the organic carbanion.     

茚基镍的卤化物/四苯硼钠/三苯基膦体系催化苯乙烯聚合

The catalytic activity of a series of indenylnickel（Ⅱ） halides： （1-R-Ind）Ni（PPh3）X （R=ethyl, cyclopentyl and benzyl, while X=Cl, Br and I）, towards styrene polymerization was studied in the presence of NaBPh4 and PPh3. The catalytic property of these halides was related to the substituent group on the indenyl ligand and the halogen atom bonded to the metal atom. Among them, the （1-Et-Ind）Ni（PPh3）Cl/NaBPha/PPh3 system showed the highest activity for the polymerization of styrene, and the polystyrene obtained was a syndio-rich （rr triad） atactic polymer with Mn values in the range of 103--104. The mechanism of the styrene polymerization initiated by the （1-Et-Ind）Ni（PPh3）Cl/NaBPha/PPh3 system was studied.     

Five coordinate rhodium(I) olefin complexes containing the ligand bis(but-3-enyl)phenylphosphine

The complexes Rh₂X₂(bbp)₂ (X = Cl, Br or I; and bbp = bis(but-3-enyl)phenylphosphine) have been prepared. These complexes have been characterized as five coordinate dimers in which the unsaturated phosphine acts as a tridentate ligand. Carbon monoxide reacts reversibly with the dimers forming the five coordinate monomeric compounds RhX(CO)(bbp). Mass spectral, infrared, Raman, and proton magnetic resonance data are consistent with the above formulations.     

ESR studies on reactions of dicyclopentadienyl dicarbonyl titanium with organic halides

ESR method was used to elucidate the mechanism of the reactions of alkyl, allyl or benzyl halides with dicyclopentadienyldicarbonyl titanium. The paramagnetic [intermediates of the reactions were identified during the course of the reactions. The reaction mechanism based on ESR findings and the products analyses is postulated to operate on radical pathways. When alkyl halides were used to react with the organometallic compound 1, the intermediate found was [Cp₂Ti(CO)X] (C), and the main product was identified to be dicyclopentadienyl-acyl-halo titanium (3), an insertion of TiCO into R-X, i.e. [Cp₂Ti-C(0)R] X. When allyl or benzyl halides were used, the intermediate found was [Cp₂TiX] (B), and the main products were identified to be the dicyclopentadienyl titanium dihalides and the coupling products of allyl or benzyl groups.     

Ti-mediated intramolecular cyclopropanation of N-alkenyl thioamides: scope and mechanistic study

Although thioamides generally undergo a reductive alkylation process when they are treated with a Grignard reagent in the presence of Ti(OiPr)₄, substrates fitted with a but-3-enyl substitution at the nitrogen atom are shown to be converted into bicyclic aminocyclopropanes. These reactions are compared with the similar cyclisations of the corresponding carboxylic amide substrates. A mechanistic study is provided. Coincidently, new reagent systems are identified for the mediation of the same transformation.     

Nickel Tetracarbonyl as Starting Material for the Synthesis of NHC-stabilized Nickel(II) Allyl Complexes

A novel, useful in situ synthesis for NHC nickel allyl halide complexes [Ni(NHC)(η³-allyl)(X)] starting from [Ni(CO)₄], NHC and allyl halides is presented. The reaction of [Ni(CO)₄] with (i) one equivalent of the corresponding NHC and (ii) with an excess of the corresponding allyl chloride at room temperature leads with elimination of carbon monoxide to complexes of the type [Ni(NHC)(η³-allyl)(X)]. This approach was used to synthesize the complexes [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 2 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 3 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 4 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Br)] ( 5 ), [Ni(Me₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 6 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 7 ). The complexes 1 to 7 were characterized using NMR and IR spectroscopy and elemental analysis, and the molecular structures are provided for 2 and 7 . The allyl nickel complexes 1 – 7 are stereochemically non-rigid in solution due to (i) NHC rotation about the nickel-carbon bond, (ii) allyl rotation about the Ni–η³-allyl axis and (iii) π–σ–π allyl isomerization processes. The allyl halide complexes can be methylated as was demonstrated by the methylation of a number of the complexes [Ni(NHC)(η³-allyl)(X)] with methylmagnesium chloride or methyllithium, which led to isolation of the complexes [Ni(Me₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 8 ), [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 9 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 10 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 11 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Me)] ( 12 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 13 ). These complexes were fully characterized including X-ray molecular structures for 10 and 11 .     

Conversion of imine ligands in allyl-nickel(II) complexes

Interaction of Ni(allyl)₂ and bidentate nitrogen-containing ligands (phenanthroline-1,10; bis(2,6-diisopropylphenyl)diazabutadiene) has been studied. It has been shown that coordination of diimine ligands proceeds with transfer of an allylnickel group to the diimine frame and formation of a covalent Ni-N bond giving rise to imine(amide)Ni(II) complexes. In the case of phenanthroline dearomatization of one heteroaromatic ring takes place. The low-spin imine(amide)allyl complexes (allyl)Ni(C₁₅H₁₅N₂) (1) and (allyl)Ni(C₂₉H₄₂N₂) (3) have been isolated as crystals and characterized by solution spectroscopy. Combining two molar equivalents of phenanthroline-1,10 with Ni(allyl)₂ results in the transfer of both allyl groups and formation of the high-spin imine(amide)Ni(II) complex Ni(C₁₅H₁₅N₂)₂ (2).     

Derivatives of phosphorous acid as a new class of ligands for Pd-catalyzed allylation

Amido- and aminophosphites and hydrospirophosphoranes can be used as ligands in the Pd-catalyzed allylation of ethyl malonate with ethyl (3-phenylprop-2-enyl) carbonate. Bidentate ligands (RO)₂P--O(CH₂)_n--NR"₂ (n = 2 and 3) were found to be the most effective ligands.     

Inter- and intramolecular palladium-catalyzed allyl cross-coupling reactions using allylindium generated in situ from allyl acetates, indium, and indium trichloride

Inter- and intramolecular palladium-catalyzed allyl cross-coupling reactions using allylindium generated in situ by treatment of allyl acetates with indium and indium trichloride in the presence of Pd(0) catalyst and nBuNMe(2) in DMF were successfully demonstrated. Allylindium species generated in situ by reductive transmetalation of pi-allylpalladium(II) complexes, obtained from a variety of allyl acetates in the presence of Pd(0) catalyst together with indium and indium trichloride, were found to be capable of acting as effective nucleophilic coupling partners in Pd-catalyzed cross-coupling reactions. A variety of allyl acetates such as but-1-en-3-yl acetate, crotyl acetate, and 2-methylallyl acetate afforded the corresponding allylic compounds in good yields in cross-coupling reactions. Various electrophilic cross-coupling partners such as aryl iodides and vinyl bromides and triflates participate in these reactions. Not only intermolecular but also intramolecular Pd-catalyzed cross-coupling reactions work equally well to produce the desired allylic coupling products in good yields.