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1.
Sterically hindered p- and o-benzoquinone methacrylates, viz., 2,5-di(tert-butyl)-3,6-di-oxocyclohexa-1,4-dienyl methacrylate and 2,5-di(tert-butyl)-3,4-dioxocyclohexa-1,5-dienyl methacrylate, were synthesized by O-acylation of the lithium and tetrabutylammonium salts of 3,6-di(tert-butyl)-2-hydroxy-p-benzoquinone with methacryloyl chloride. The influence of the nature of cation and solvent on regioselectivity of the acylation was studied. The o-benzoquinone derivative obtained can serve as a paramagnetic ligand in metal complexes.  相似文献   

2.
Reactions of triguanidinate lanthanide complexes Ln[(iPrN)(NC6H4p-Cl)C(NHiPr)]3 (Ln = Nd, Y) with 3 equiv. of n-BuLi gave [Li(THF)(DME)]3Ln[μ-η2η1 (iPrN)2C(NC6H4p-Cl)]3, which represents the first structurally characterized complexes of lanthanide and lithium metals with dianionic guanidinate ligands. The Nd complex was found to be an effective catalyst for amidation of aldehydes with amines under mild conditions with a wide scope of substrates.  相似文献   

3.
Treatment of ortho-carborane, n-butyl lithium, selenium and [(p-cymene)RuCl2]2 under argon leads to complexes (p-cymene)Ru(Se2C2B10H10) (I) and (p-cymene)2Ru22-Se2C2B10H10) (II). The further reaction of 16-electron complex I with RC≡CCO2Me affords addition complexes (p-cymene)Ru(Se2C2B10H10)(RC=C-CO2Me) (III) (R = H (IIIa); CO2Me (IIIb)). These complexes were characterized by elemental analysis, mass, and NMR spectroscopy. X-ray structural analyses were performed on II and IIIa.  相似文献   

4.
Hanna K. Cotton 《Tetrahedron》2006,62(24):5632-5640
Screening of metallocenethiolate ligands for copper(I)-catalyzed substitution of allylic acetates with Grignard reagents has been carried out. The previously used ligand, lithium (R,Sp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4a), possessing both central and planar chirality, was the starting point for the screening. It was found that the diastereomeric ligand lithium (R,Rp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4b) exhibiting reversed planar chirality gave increased enantioselectivity in the allylic substitution, at least when cinnamyl acetate was used as a substrate. The ruthenocene-based ligand lithium (R,Sp)-2-(1-dimethylaminoethyl)ruthenocenylthiolate (4c) gave an enhanced reaction rate, but lower chiral induction. The use of disulfide bis[(R,Sp)-2-(1-dimethylaminoethyl)ferrocenyl]disulfide (7a) as a ligand precursor worked well but resulted in lower enantioselectivity.  相似文献   

5.
The electronic structure of cobalt complexes with bi-, tri-, and tetradentate ligands and the mutual influence of ligands in them have been studied by X-ray photoelectron spectroscopy. The Co2p, N1s, and O1s photoelectron spectra have been studied. Unlike low-spin Co(III) complexes, the high-spin Co(II) compound exhibits a strong satellite line in the Co2p spectrum. For the high-spin Co(II) compound having unpaired 3d electrons, the Co2p 1/2-Co2p 3/2 spin-orbit splitting is larger than that in the low-spin Co(III) complexes. All cobalt complexes under consideration contain strongly bound dioxygen, which can be considered an inherent structural unit.  相似文献   

6.
Daisuke Wakasugi 《Tetrahedron》2005,61(5):1245-1256
Reaction of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from chloromethyl p-tolyl sulfoxide and ketones in high overall yields, with cyanomethyllithium (lithium α-carbanion of acetonitrile) gave adducts in high to quantitative yields. The adducts were treated with LDA followed by lithium α-carbanion of the homologues of acetonitrile to give 3,5,5-trisubstituted enaminonitriles in good to high yields. Hydrolysis of the enaminonitriles under acidic conditions gave 2,4,4-trisubstituted 2-cyclopentenones in good yields. By using the optically active chloromethyl p-tolyl sulfoxide and unsymmetrical ketones, this procedure gave the optically pure 2,4,4-trisubstituted 2-cyclopentenones. The scope and limitations of this method and the mechanism of the reactions are also discussed. These procedures offer a new and effective method for the synthesis of 2,4,4-trisubstituted 2-cyclopentenones from four components, ketones, chloromethyl p-tolyl sulfoxide, acetonitrile, and its homologues.  相似文献   

7.
1-Chlorovinyl p-tolyl sulfoxides were synthesized from several kinds of ketones and chloromethyl p-tolyl sulfoxide in three steps in high overall yields. Treatment of the 1-chlorovinyl p-tolyl sulfoxides with cyanomethyllithium (lithium α-carbanion of acetonitrile) at low temperature gave the adducts in almost quantitative yields. The adducts were then treated with LDA followed by excess lithium α-carbanion of the homologues of acetonitrile to afford 3,5,5-trisubstituted cyclopentadienyl enaminonitriles, which were hydrolyzed and heated under acidic conditions to give 2,4,4-trisubstituted 2-cyclopentenones in good overall yields.  相似文献   

8.
《Tetrahedron: Asymmetry》1999,10(20):3991-3998
Chiral lithium amides are being developed for stereoselective synthesis of chiral allylic alcohols in high yields and with high enantiomeric excess. However, rational design of the amides for improved stereoselectivity by computational methods, for example, has not been possible due to lack of knowledge of the activated complexes involved in the reactions. Kinetic results are presented for the stereoselective deprotonation by lithium (S)-1-(2-pyrrolidinylmethyl)pyrrolidide (1-Li) of cyclohexene oxide 2, in diethyl ether (DEE), to form (S)-2-cyclohexen-1-ol (S)-3 in high enantiomeric excess. The results show that the rate limiting activated complex is composed of one lithium amide monomer and one molecule of 2 and presumably a solvent molecule. The diamine 1 is found to catalyze the deprotonation.  相似文献   

9.
m- or p-Iodinated, or brominated ω-phenoxyalcohols and phenols as well as halogenated indoles were subjected to halogen-magnesium exchange reactions with isopropyl magnesium bromide (iPrMgBr) or isopropyl magnesium di-n-butyl lithium ate complexes (iPrMgnBu2Li) at −78 °C to room temperature. iPrMgnBu2Li proved superior to prevent ortho-metallation of these substituted arenes.  相似文献   

10.
José L. García Ruano 《Tetrahedron》2004,60(44):10067-10075
(S)-ortho-(p-Tolylsulfinyl)benzyl alkyl (and aryl) ketones 1a-e were prepared in good yields by reaction of esters or nitriles with the lithium benzyl carbanion derived from 2-(p-tolylsulfinyl) methylbenzene. α-Methylbenzyl ketones 2 were prepared as ca. 1:1 diastereoisomeric mixtures by methylation of the unsubstituted ketones 1 with NaH/MeI. The use of the ethylbenzene derivative as the starting material afforded complex mixtures. The obtention of pure (S,(S)S)-2 diastereoisomers could be attained in good yields by oxidation with PCC of the alcohols (epimeric mixtures at the hydroxylic carbon) obtained from reactions of aldehydes with the lithium carbanion derived from 2-(p-tolylsulfinyl)ethylbenzene.  相似文献   

11.
The addition reactions of 1-chlorovinyl p-tolyl sulfoxides, which were derived from ketones and chloromethyl p-tolyl sulfoxide, with lithium acetylides gave adducts in moderate to good yields. Treatment of the adducts with Grignard reagents resulted in the formation of conjugated enynes in good to high yields via the 1,2-carbon-carbon insertion (1,2-CC insertion) reaction of the generated magnesium carbenoid intermediates. On the other hand, the addition reactions of 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes with lithium acetylides directly gave conjugated enynes bearing a p-tolyl sulfinyl group at the 1-position through the 1,2-carbon-hydrogen insertion (1,2-CH insertion) reaction of the generated lithium carbenoid intermediates. These procedures provide a good way for the synthesis of multi-substituted conjugated enynes from ketones and aldehydes.  相似文献   

12.
《Polyhedron》1988,7(9):725-730
Bis(cyclopentadienyl)metal complexes of calcium, strontium and barium can be prepared in synthetically useful yields (> 65%) from the reaction of lithium or potassium cyclopentadienides and the appropriate metal dihalides in THF. The THF-soluble complexes (C5H5)2Ca(THF)2 and (Me5C5)2M(THF)2 (M = Ca, Sr, Ba) are extracted from the reaction of the appropriate potassium cyclopentadienide with a metal halide; the THFinsoluble (C5H5)2M(THF)x(x ≈ 1 for Sr; x ≈ 0.25 for Ba) remain after the reaction of a lithium cyclopentadienide and the metal iodide.  相似文献   

13.
Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were derived from cyclobutanones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl carboxylates, amides, lithium α-sulfonyl carbanions, and lithium α-carbanion of acetonitrile gave adducts in high to quantitative yields. The adducts were treated with Grignard regents, such as i-PrMgCl and EtMgCl in toluene to afford 1-substituted cyclopentenes in good to high yields with one-carbon ring-expansion via 1,2-carbon-carbon (1,2-CC) insertion reaction of the generated magnesium carbenoid intermediates. The magnesium carbenoid 1,2-CC insertion was found to be highly stereospecific. When optically pure chloromethyl p-tolyl sulfoxide was used in this procedure, optically active 1-substituted cyclopentenes were obtained in high optical purity.  相似文献   

14.
p-Cymene complexes MCl26-p-cymene)L [M = Ru, Os; L = P(OEt)3, PPh(OEt)2, (CH3)3CNC] were prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with phosphites or tert-butyl isocyanide. Treatment of MCl26-p-cymene)L complexes with 1,3-ArNNN(H)Ar triazene and an excess of NEt3 gave the cationic triazenide derivatives [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 (Ar = Ph, p-tolyl). Neutral triazenide complexes MCl(η2-1,3-ArNNNAr)(η6-p-cymene) (M = Ru, Os) were also prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with 1,3-diaryltriazene in the presence of triethylamine. p-Cymene complexes MCl26-p-cymene)L reacted with equimolar amounts of 1,3-ArNNN(H)Ar triazene to give both triazenide complexes [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 and amine derivatives [MCl(ArNH2)(η6-p-cymene)L]BPh4. A reaction path for the formation of the amine complex is also reported. The complexes were characterised by spectroscopy and X-ray crystallography of RuCl26-p-cymene)[PPh(OEt)2] and [Ru(η2-1,3-p-tolyl-NNN-p-tolyl)(η6-p-cymene){CNC(CH3)3}]BPh4. Selected triazenide complexes were studied as catalysts in the hydrogenation of 2-cyclohexen-1-one and cinnamaldehyde.  相似文献   

15.
Mono- and binuclear nickel complexes of different stoichiometry have been studied by X-ray photoelectron spectroscopy (XPS). The Ni2p, Ni3p, and N1s X-ray photoelectron spectra have been examined, and the role of a ligand in their formation has been determined. As distinct from a low-spin Ni(II) complex, the Ni2p spectra of high-spin Ni(II) compounds show strong satellite lines. For high-spin Ni(II) complexes, which have unpaired 3d electrons, the Ni2p 1/2-Ni2p 3/2 spin-orbit splitting is larger than that for a low-spin Ni(II) compound. The presence or absence of the satellite structure has made it possible to classify these complexes with regard to their magnetic properties. The difference between the Ni2p 3/2 and N1s binding energies has made it possible to estimate the covalence of the metal-ligand bond. The XPS results are consistent with X-ray crystallography data.  相似文献   

16.
Palladium(II) complexes of biacetylmonoxime arylhydrazones (HL, aryl = phenyl, o-, m-, and p-tolyl, p-chloro- and p-nitrophenyl) and biacetylmonoxime N′-methyl-phenylhydrazone (HL′) have been prepared and characterized. The hydrazomines, HL and HL′, are coordinated through oxime- and hydrazone-nitrogen atoms as a bidentate ligand in the complexes [PdX2(HL or HL′)] (X = halogen atom) formed under neutral conditions. Under basic conditions the deprotonated complexes [PdX(L or L′)] are obtained. Deprotonation occurs at the oxime group of HL′ and the ligand remains coordinated through oxime- and hydrazone-nitrogen atoms. The other hydrazoximes (HL) are cyclopalladated at the ortho position of the benzene rings and act as an NNC terdentate ligand in the deprotonated complexes [PdXL].  相似文献   

17.
The reactions of a range of 2-arsa- and 2-stiba-1,3-dionato lithium complexes with group 4-7 metals have been investigated. These have given rise to several complexes in which an arsadionate acts as a chelating ligand; [V{η2-O,O-OC(But)AsC(But)O}3], [M{η2-O,O-OC(But)AsC(But)O}2(DME)], M=Cr or Mn; or as an η1-As-diacylarsenide, [MnBr(CO)4{As[C(O)But]2Li(DME)}]2. In addition, reactions of lithium arsadionates with TaCl5 have led to metal mediated arsadionate decomposition reactions and arsadionate oxidative coupling reactions to give the known arsaalkyne tetramer, As4C4But4, and the new tetraacyldiarsane, [{As[C(O)Mes]2}2] Mes=mesityl, respectively. The treatment of several lithium arsadionates with [MoBr2(CO)2(PPh3)2] has also initiated arsadionate decomposition reactions and the formation of the metal carboxylate complexes, [MoBr(CO)22-O2C(R)}(PPh3)2] R=But, Ph, Mes. The X-ray crystal structures of six of the prepared complexes are discussed.  相似文献   

18.
Enantioselective preference in the asymmetric synthesis where cyclohexene oxide is transformed enantioselectively to chiral (S)- or (R)-2-cyclohexen-1-ol by the reaction with the appropriate chiral lithium amide reagent has been evaluated theoretically using the MM3 force field. The plausible possible structures for each precursor (reaction intermediate complex) leading to a (S)- or (R)-2-cyclohexen-1-ol have been optimized with the extended MM3 force field applicable to the lithium amide functional group, and the populations of their (S)- or (R)-reaction intermediate complexes at an ambient temperature (298 K) were calculated. The initial structure for evaluating the reaction intermediates of this asymmetric synthesis was constructed on the basis of the optimized ab initio transition state structure (MP2/6-31+G) comprising lithium amide LiNH2 and propene oxide. To the thus obtained transition state structure composed of LiNH2 and propene oxide, the other remaining Cartesian coordinates for the actual reaction intermediates composed of the chiral lithium amides and cyclohexene oxide were added to make the reaction intermediate structure. The conformational search for the reaction intermediate has been carried out by using the Stochastic search Algorithm, and the optimized geometries and their conformational energies (steric energies) have been calculated by the MM3 force field. The populations calculated from the conformational energies of the reaction intermediate leading to the (S)- or (R)-2-cyclohexen-1-ol were shown to be linearly well correlated with the experimentally reported enantiomer excess (% ee) values. The critical factors to control the enantioselectivity were investigated on the basis of the optimized structures of the reaction intermediate complexes. The MM3 force field approach was shown to be applicable to the theoretical evaluation of the enantioselectivity and be useful for designing a new functional chiral lithium amide reagent for the asymmetric synthesis.  相似文献   

19.
《Solid State Sciences》2012,14(7):880-884
A flexible dicarboxylic acid having composition [(CH(o-C5H4N)(p-C6H4OCH2CO2H)2] derived from corresponding bis-phenol reacts with various metal(II) acetates such as manganese(II), cobalt(II) and nickel(II) acetate leads to zwtterionic complexes with compositions [CH(o-C5H4N)(p-C6H4OCH2CO2){p-C6H4OCH2CO2M(H2O)5}].6H2O (where M = Mn, Co, Ni). The complexes are characterised by X-ray crystallography. These complexes have chiral center due to unsymmetric structure conferred to the ligand through coordination at only one carboxylate group of the ligand. In solid state these complexes are racemic.  相似文献   

20.
Reaction of a series of directly connected oxazoline-imidazolium salts with silver(I) oxide and subsequent transmetallation with [Ru(p-cymene)Cl2]2 and anion exchange with KPF6 cleanly gave the corresponding 2-oxazolinyl-(N-mesityl)imidazolidene(chloro)ruthenium(II) half-sandwich complexes [RuCl(oxcarb)(p-cymene)]PF6, two derivatives of which were characterized by X-ray diffraction. Abstraction of the chloro ligand furnished the dicationic aqua complexes [Ru(H2O)(oxcarb)(p-cymene)](PF6)2 which possess a similar coordination geometry. The syntheses were found to be highly diastereoselective, since only one diastereoisomer could be observed in all ruthenium complexes upon reaction of the chiral enantiopure oxazoline-imidazolium salts. Their potential as transfer hydrogenation and Lewis acid catalysts has been probed.  相似文献   

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