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1.
N-heterocyclic carbene (NHC) complexes of rhodium(I) (3 and 4) bearing one diether (MeOCH2CH2OCH2CH2-NHC) functionality on N1 and bulky benzyl groups (CH2-C6H2(CH3)3-2,4,6 and CH2-C6(CH3)5) on N3 of (5,6-dimethyl)benzimidazole were synthesized by deprotonation of the corresponding benzimidazolium salt with [Rh(μ-OMe)(1,5-cod)]2 in dichloromethane at ambient temperature. All compounds have been fully characterized by elemental analysis, 1H and 13C NMR spectroscopy. X-ray diffraction studies on single crystals of 3a and 3b confirm the cis square planar geometry. All of the new benzimidazol-2-ylidene rhodium(I) complexes were found to be effective catalysts for the transfer hydrogenation reaction. 相似文献
2.
《Chirality》2017,29(12):798-810
Enantiomerically pure secondary alcohols are essential compounds in organic synthesis and are used as chiral auxiliaries and synthetic intermediates in the pharmaceutical, agrochemical, and fine chemical industries. One of the attractive and practical approaches to achieving optically pure secondary alcohols is oxidative kinetic resolution of racemic secondary alcohols using chiral Mn(III) salen complexes. In the last decade, several chiral Mn(III) salen complexes have been reported with excellent enantioselectivity and activity in the homogeneous and heterogeneous catalysis of the oxidative kinetic resolution of racemic secondary alcohols. This review article is an overview of the literature on the recent development of chiral Mn(III) salen complexes for oxidative kinetic resolution of racemic secondary alcohols. The catalytic activity of monomeric, dimeric, macrocyclic, polymeric, and silica/resin supported chiral Mn(III) salen complexes is discussed in detail. 相似文献
3.
The electrochemical properties of cationic complexes [(η6-arene)Ru(N ∩ N)Cl]Cl (arene/N ∩ N = C6H6/1,10-phenanthroline (1), p-MeC6H4Pri/1,10-phenanthroline (2), C6Me6/1,10-phenanthroline (3), C6Me6/5-NO2-1,10-phenanthroline (4), and C6Me6/5-NH2-1,10-phenanthroline (5)) were studied by cyclic voltammetry in order to rationalize catalytic activity in transfer hydrogenation of the respective aqua complexes [(η6-arene)Ru(N ∩ N)(OH2)](BF4)2 (6-10). Complexes 1-5 were chosen because the ‘true’ catalysts 6-10 are unstable under the conditions of the measurement. The electrochemical behaviour of 1-5 in acetonitrile solution is rather complicated due to consecutive and parallel chemical reactions that accompany electron transfer processes. Nonetheless, interpretation of the electrochemical data allowed to assess the influence of the structure and substitution on the redox and catalytic properties: the catalytic ability correlates with the reduction potentials, indicating the decisive role of the η6-arene ring directly bonded to the catalytic centre (Ru). 相似文献
4.
Xiawei Zhang 《Inorganica chimica acta》2011,369(1):253-14569
The transfer dehydrogenation of several ketones by (PCP)IrH2 (PCP = κ3-C6H3-2,6-(CH2PtBu2)2) (1) has been observed. Catalytic turnover was inhibited in most cases by the formation of stable metallacycles or the O-H oxidative addition of phenolic products. Catalytic transfer dehydrogenation of 3,3-dimethylcyclohexanone was achieved, giving the corresponding α,β-enone. The transfer dehydrogenation reaction of cycloheptanone with 1 was found to generate a surprisingly stable PCP-iridium troponyl hydride (9), which is stabilized by conjugation and possibly represents an unusual bicyclo[5.2.0]troponyliridium metalloaromatic structure. Complex 9 was found to catalyze the dimerization of tropone to give a fused tricyclic dihydrodicycloheptafuranol. A mechanism for this reaction is proposed wherein the coordinated troponyl group nucleophilically attacks a free tropone molecule. 相似文献
5.
Montserrat Diéguez Aurora Ruiz Franco Doro Serafino Gladiali 《Inorganica chimica acta》2004,357(10):2957-2964
Mononuclear cationic Ir(I)-cyclooctadiene complexes containing three different C2-symmetrical binaphthalene-templated sulfide ligands, featuring alkyl groups of increasing steric demand onto the donor centres, have been prepared and characterized. Variable temperature NMR spectra provide evidence that, regardless of the bulk of the alkyl substituent on the sulfur, the chelate coordination of the ligands proceeds in all cases with complete stereoselectivity at the newly generated S-stereocentres affording just one stereoisomer. This species features a seven-membered chelate ring in a frozen conformation where the diequatorial S-alkyl substituents are disposed in anti-relationship and the stereogenic S-donors display the same configuration. The oxidative addition of hydrogen to these complexes proceeds smoothly affording in every case one single cis-dihydride complex whose structure in one case has been cleared by correlated NMR spectra. The cationic complexes derived from these ligands are catalysts of modest value for the hydrogenation of α,β-unsaturated acid derivatives where they produce nearly racemic products in moderate yields. 相似文献
6.
Urszula Kalinowska Magdalena Ma?ecka Bernhard Lippert 《Inorganica chimica acta》2005,358(8):2464-2472
The synthesis of diethyl (pyridin-2-, -3-, -4-ylmethyl)phosphate (2-pmOpe, 3-pmOpe, 4-pmOpe) ligands and their palladium (II) complexes of general formula trans-[PdCl2L2] (L = 2-pmOpe, 3-pmOpe,4-pmOpe) has been described. Pyridine phosphate derivatives were synthesized via the condensation of phosphorochloridic acid diethyl ester with an appropriate pyridinylmethanol in the presence of triethylamine. The compounds have been identified and characterized by IR, far-IR, 1H NMR, 31P NMR, 31P CP-MAS NMR and elemental analyses. The crystal and molecular structures of palladium (II) complexes, i.e., [PdCl2(2-pmOpe)2] and [PdCl2(4-pmOpe)2] determined by the X-ray diffraction method, are presented. In both structures, Pd(II) ions are four-coordinated by two chlorine atoms and two pyridine nitrogen atoms. The geometry of complexes is square-planar and adopt a trans configuration, which is consistent with preparation method. 相似文献
7.
Samantha N. MacMillan 《Inorganica chimica acta》2009,362(9):3134-14103
The reaction of the racemic and resolved tetrahydrosalen derivative LH2 (LH2 = N,N’-bis(3,5-dichloro-2-hydroxybenzyl)-trans-1,2-diaminocyclohexane) with the resolved titanium(IV) sec-butoxides Ti(OR-2Bu)4 or Ti(OS-2Bu)4 yielded a series of four compounds, LTi(O2Bu)2 (1-4), which have been characterized by IR, elemental analysis, 1H and 13C NMR and X-ray crystallography. X-ray crystallography revealed the co-crystallization of two pseudo-C2-symmetric products from racemic LH2, whereas a perfect chiral induction of the ligand to the metal occurred when resolved (R,R)-LH2 was used, resulting in a Δ fac-fac wrapping mode of the tetradentate ligand about the titanium center. Ab initio electronic structure calculations (DFT) are in agreement that the lowest energy isomer is that which is experimentally observed. Catalysis screenings show that Ti(OS-2Bu)4, in conjunction with (R,R)-LH2, forms a matched pair that catalyzes the addition of dimethyl zinc to benzaldehyde with higher enantioselectivity than that observed for resolved (R,R)-LH2 with Ti(OR-2Bu)4 or achiral Ti(OiPr)4. Increasing the temperature of the system results in slightly increased enantiomeric excess. 相似文献
8.
New chiral amidophosphite ligand was synthesized and tested in the Rh‐catalyzed asymmetric hydrogenation of (Z)‐β‐(acylamino)acrylates in protic solvents and supercritical carbon dioxide (scCO2) The catalytic performance is affected greatly by the acidity of the solvents. Better enantioselectivity (up to 88% ee) was achieved in scCO2 containing 1,1,1,3,3,3‐hexafluoro‐2‐propanol, compared to neat protic solvents. Chirality, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
9.
Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions
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A few new d ‐mannitol‐based monoaza‐15‐crown‐5 type chiral lariat ethers and 18‐crown‐6 type macrocycles were synthesized. These crown compounds were used as phase transfer catalysts in asymmetric Michael addititons and in a Darzens condensation under mild conditions to afford the corresponding products in a few cases in good to excellent enantioselectivities. In the Michael addition of diethyl acetoxymalonate to trans‐chalcone, in the addition of diethyl acetamidomalonate to ß‐nitrostyrene, in the reaction of diethyl bromomalonate with benzylidene malononitriles, in the cyclopropanation reaction of diethyl bromomalonate and 2‐benzylidene‐1,3‐indandione, and in the Darzens condensation of α‐chloroacetophenone with benzaldehyde, maximum enantioselectivities of 39%, 65%, 99%, 56%, and 62%, respectively, were obtained in the presence of the d ‐mannitol‐based macrocycles as the catalysts. 相似文献
10.
In this contribution, the synthesis and characterization of eight ruthenium(II) carbonyl complexes supported by chelating alkane-bridged bis-N-heterocyclic carbene ligands are reported. The products obtained are analyzed using infrared and NMR spectroscopies. The molecular structures of four metal complexes were determined by X-ray crystallography, which exhibit the six-coordinate octahedral geometry with two carbene carbon atoms from the bidentate Bi-NHCs, two carbonyl groups and two chlorine atoms in the trans(Cl)-cis(CO) configuration. All these complexes show catalytic activities in transfer hydrogenation of ketones. 相似文献
11.
For the optical resolution of racemic 1-phenylethylamine in 3-methyl-3-pentanol, subtilisin was reformulated by lyophilization
with buffer salts. The amide synthesis activity of subtilisin in organic solvent was compared with the hydrolysis activity
in aqueous buffer when different buffer species and their concentrations were used in lyophilization. The enzyme activity
in organic solvent showed a different pattern from that of the hydrolysis depending upon the species and the concentrations
of buffers. Morphology of the reformulated subtilisin was examined by scanning electron microscopy (SEM). The porosity of
reformulated subtilisin particles increased up to the optimal buffer concentrations for the amide synthesis in organic solvent.
Glassy looks and decrease in porosity developed at high (i.e. above the optimal) buffer concentrations appear to affect the decrease in the synthetic activity in organic media. 相似文献
12.
(R,R)‐formoterol was synthesized in seven steps with 4‐hydroxyl‐3‐nitro‐acetophenone as the starting material. The key intermediate, the chiral secondary alcohol 4 , was prepared via Rh‐catalyzed asymmetric transfer hydrogenation with (S,S)‐PEGBsDPEN as the ligand and sodium formate as the hydrogen donor under mild conditions. With a mixture of PEG 2000 and water as the reaction media, the catalyst system could be recycled four times. Chirality, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
13.
The ability of transition metal catalysts to add or remove hydrogen from organic substrates by transfer hydrogenation process is a valuable synthetic tool. For this aim, a novel Ru(II) complex with the P-N ligand [(Ph2P)2NCH2-C4H3S] derived from thiophene-2-methylamine was synthesized starting with the complex [Ru(η6-p-cymene)(μ-Cl)Cl]2 and isolated in two isomeric forms: trans- and cis-[Ru((PPh2)2NCH2-C4H3S)2Cl2], 2 and 3, respectively. The structures of both isomers were also determined by single crystal X-ray diffraction. The cis-isomer 3 can be isolated from the solution of major trans-isomer 2 as yellow crystals. However, upon dissolution 3 is rapidly converted to the trans-isomer 2. The new ruthenium(II) complex provides high catalytic activity in the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. This transfer hydrogenation is characterized by low reversibility under the experimental conditions. 相似文献
14.
Optically pure C1- and C2-terpyridine ligands (L) form cobalt(II) and iron(II) complexes of formula [Co(L)Cl2] and [Fe(L)Cl2], respectively, and Iron(III) complexes of formulas [Fe(L)Cl3]. Structures of three new chiral cobalt(II) and one iron(III) complexes were analysed using X-ray crystal structure analysis. These complexes were shown to be precursor of efficient catalyst for cyclopropanation. Reaction with AgOTf converted the complex to active catalyst, which gave enantioselectivities of up to 76% ee for the trans-isomers and 83% ee for the cis-isomers of styrene cyclopropanes with ethyl diazoacetate. Hammett studies showed the active species for both cobalt and iron complexes to have a non-linear relationship to σp constant. 相似文献
15.
Catalytic asymmetric synthesis of alpha,beta-epoxy esters and alpha,beta-epoxy carboxylic acid derivatives is described. Catalytic asymmetric epoxidation of alpha,beta-unsaturated carboxylic acid imidazolides using La-BINOL-Ph(3)As=O complex gave the corresponding alpha,beta-epoxy peroxy tert-butyl esters, which were directly converted to the alpha,beta-epoxy methyl esters by adding methanol to the reaction. This catalytic system had broad generality for epoxidation of various substrates. With the use of 5-10 mol% of the catalyst, both beta-aryl and beta-alkyl-substituted-alpha,beta-epoxy methyl esters were obtained in up to 91% yield and in up to 93% enantiomeric excess. In addition, efficient transformations of alpha,beta-epoxy peroxy tert-butyl esters into the alpha,beta-epoxy amides, alpha,beta-epoxy aldehydes, and gamma,delta-epoxy beta-keto esters are also reported. 相似文献
16.
Manuel Basauri-Molina 《Inorganica chimica acta》2010,363(6):1222-1229
The sterically hindered thiolate complexes [Pd(SR)2(TMEDA)] SR = SC6F5 (2), SC6F4-4-H (3), SC6H4-2-SiPh3 (4) were easily synthesized by metathetical reactions of the corresponding palladium chloro compound [Pd(Cl)2(TMEDA)] (1) and the lead salt of the corresponding thiol. The identity of the three species being unequivocally determined by single crystal X-ray diffraction techniques. The catalytic activity of the palladium species [Pd(SR)2(TMEDA)] was explored in the Suzuki-Miyaura cross coupling reactions of different p-substituted bromobenzenes. 相似文献