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1.
A new chiral 1,4-diphosphine, 1,4:3,6-dianhydro-2,5-dideoxy-2,5-bis(diphenylphosphino)-l-iditol, has been prepared from d-mannitol. Rhodium complexes of this ligand are asymmetric homogeneous hydrogenation catalysts for dehydroamino acids, giving (S)-amino acids in 21–58% optical yields. 相似文献
2.
The C18–C26 fragment of amphidinolide C congeners has been synthesized starting from methyl acetoacetate in 14 steps in >17.0% overall yield. The C20 stereogenic center was secured by asymmetric hydrogenation of a β-keto ester and the configuration at both C23 and C24 was introduced by asymmetric dihydroxylation (AD). The trans-2,5-disubstituted tetrahydrofuran ring was assembled via the tandem AD–SN2 sequence. The latter protocol could be employed for accessing the corresponding cis-2,5-disubstituted tetrahydrofuran rings from the same alkene substrates simply by choosing a suitable AD ligand. Moreover, functional group compatibility was observed for the Ru(II)-catalyzed hydrogenation of β-keto esters and the Pd(0)–Cu(I)-catalyzed Sonogashira cross-coupling reaction. These findings should be valuable for general synthetic design and application. 相似文献
3.
《Tetrahedron: Asymmetry》2007,18(11):1278-1283
The catalytic asymmetric hydrogenation of prochiral ketones was carried out with Ru(II) complexes prepared from new chiral diphosphine ligands, cis-(R,R)-2,5-bis[(diarylphosphino)]-3-hexenes. These new ligands were prepared from enantiomerically pure (R,R) or (S,S)-(Z)-3-hexene-2,5 diol and enantiomeric excesses up to 85% were obtained in the reduction of 2-benzamidomethyl-3-oxobutanoate, starting material for the synthesis of 4-acetoxy-2-azetidinone. 相似文献
4.
?rt Malavaši?Uroš Grošelj Amalija Golobi?Jure Bezenšek Branko Stanovnik Katarina Stare Jernej WaggerJurij Svete 《Tetrahedron: Asymmetry》2011,22(6):629-640
Eleven (S)-1,6-dialkylpiperazine-2,5-diones and five (3S,6S)-1,3,6-trialkylpiperazine-2,5-diones were prepared in three steps from the corresponding (S)-α-amino acid esters comprising of reductive N-alkylation, N-acylation and cyclisation. The synthesis of (S)-1,6-dialkylpiperazine-2,5-diones has a broad scope allowing preparation of diketopiperazines with primary and secondary alkyl groups at N(1), while the synthesis of (3S,6S)-1,3,6-trialkylpiperazine-2,5-diones is limited to compounds with primary alkyl groups at N(1). Reductive alkylation of amino acid ester hydrochlorides by catalytic hydrogenation in the presence of a carbonyl compound proved to be a simple, efficient and general method for the preparation of stable (storable) α-alkylamino acid ester hydrochlorides. The structures of the novel compounds were determined by NMR and X-ray diffraction. 相似文献
5.
《Journal of organometallic chemistry》1987,322(1):65-70
The chiral ansa-titanocene derivative 1,3-propanediylbis(4,5,6,7-tetrahydro-1-indenyl)titanium(IV) dichloride has been prepared by reaction of the dilithium salt of 1,3-bis(indenyl)propane with TiCl4 and subsequent hydrogenation. The product has been shown by an X-ray diffraction study to be the R,S metal-ring linkage isomer; in this trimethylene-bridged ansa-metallocene the axial symmetry previously observed for te ethylene-bridged congener is destroyed by a non-symmetric location of the (CH2)3 bridge. 相似文献
6.
《Tetrahedron: Asymmetry》2001,12(17):2385-2387
A total synthesis of (S)-(−)-acromelobinic acid 2, which was isolated from clitocybe acromelalga, was achieved via an asymmetric hydrogenation protocol. Dehydroamino acid derivative 12 was prepared from 2,5-lutidine 5 and subjected to asymmetric hydrogenation using (S,S)-[Rh(Et-DuPHOS)(COD)]BF4 to give the (S)-(+)-pyridylalanine derivative 13 in 93% yield and >96% e.e. Removal of the protecting groups in (S)-(+)-13 afforded (S)-(−)-acromelobinic acid 2. 相似文献
7.
Ferdinand R.W.P. Wild Marek Wasiucionek Gottfried Huttner Hans H. Brintzinger 《Journal of organometallic chemistry》1985,288(1):63-67
The chiral ansa-zirconocene derivative ethylenebis(4,5,6,7-tetrahydro-1-indenyl)-zirconium(IV) dichloride has been prepared by reaction of dilithiobis(indenyl)ethane with ZrCl4 and subsequent hydrogenation. The product has been shown to be the 1-R,S rather than meso-metal-ring linkage stereoisomer by an X-ray determination of the molecular structure. 相似文献
8.
Z.N. Parnes Yu.I. Lyakhovetsky M.I. Kalinkin D.N. Kursanov L.I. Belenkii 《Tetrahedron》1978,34(11):1703-1705
It has been found that 2,5-dimethylthiophenium and 2,3,5-trimethylthiophenium tetrachloroaluminates react with triethylsilane and diphenylsilane in the presence of HCl to form the corresponding thiophanes. This fact in the light of the ionic hydrogenation mechanism has led to the proposal of a new hydrogenating system: HSiEt3-HCl/AlCl3). This system has been successfully used for hydrogenating thiophenes such as 2,5-dimethyl-, 2-ethyl- and 2,5-diphenylthiophene to the respective thiophanes. It has been also extended to branched olefines, 1-methylcyclohexene being hydrogenated in high yield to methylcyclohexane. 相似文献
9.
Feyyaz Durap Murat Aydemir Duygu Elma Akın Baysal Yılmaz Turgut 《Comptes Rendus Chimie》2013,16(4):363-371
Asymmetric transfer hydrogenation processes of ketones with chiral molecular catalysts are attracting increasing interest from synthetic chemists due to their operational simplicity. C2-symmetric catalysts have also received much attention and been used in many reactions. A series of new chiral C2-symmetric bis(phosphinite) ligands has been prepared from corresponding amino acid derivated amino alcohols or (R)-2-amino-1-butanol through a three- or four-step procedure. Their structures have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. 1H-31P NMR, DEPT, 1H-13C HETCOR or 1H-1H COSY correlation experiments were used to confirm the spectral assignments. In situ prepared ruthenium catalytic systems were successfully applied to ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives by iso-PrOH. Under optimized conditions, these chiral ruthenium catalyst systems serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as good catalysts, giving the corresponding optical secondary alcohols in 99% yield and up to 79% ee. 相似文献
10.
《Tetrahedron: Asymmetry》2005,16(19):3205-3210
Enantioselective reduction of representative 2-(bromoacetyl)- and 2-(chloroacetyl)benzofurans with (−)-B-chlorodiisopinocampheylborane and by transfer hydrogenation with formic acid/triethylamine in the presence of RhCl[R,R-TsDPEN](C5Me5) is described. Transfer hydrogenation of the chloro ketones produced the corresponding chlorohydrins of ⩾95% ee. (R)-Bufuralol of 96% ee was prepared from the corresponding chloro ketone by transfer hydrogenation–substitution. 相似文献
11.
Peili Zhang Xia Sheng Xiaoyu Chen Zhiyong Fang Jian Jiang Mei Wang Fusheng Li Lizhou Fan Yansong Ren Biaobiao Zhang Brian J. J. Timmer Mrten S. G. Ahlquist Licheng Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9253-9257
The use of water as an oxygen and hydrogen source for the paired oxygenation and hydrogenation of organic substrates to produce valuable chemicals is of utmost importance as a means of establishing green chemical syntheses. Inspired by the active Ni3+ intermediates involved in electrocatalytic water oxidation by nickel‐based materials, we prepared NiBx as a catalyst and used water as the oxygen source for the oxygenation of various organic compounds. NiBx was further employed as both an anode and a cathode in a paired electrosynthesis cell for the respective oxygenation and hydrogenation of organic compounds, with water as both the oxygen and hydrogen source. Conversion efficiency and selectivity of ≥99 % were observed during the oxygenation of 5‐hydroxymethylfurfural to 2,5‐furandicarboxylic acid and the simultaneous hydrogenation of p‐nitrophenol to p‐aminophenol. This paired electrosynthesis cell has also been coupled to a solar cell as a stand‐alone reactor in response to sunlight. 相似文献
12.
《Tetrahedron: Asymmetry》1999,10(15):2951-2959
A new class of C2-symmetric pyrrolidine derivatives bearing arylethynyl groups at the 2,5-positions has been synthesized in enantiomerically pure form from 1,7-octadiyne-3,6-diol in five steps. Some notable features of the synthesis are: (i) the formation of a separable diastereomeric mixture of pyrrolidine carbamates using a newly prepared chiral chloroformate; and (ii) the development of a new method for the deprotection of the carbamate via a novel SmI2-promoted electron transfer process. 相似文献
13.
J. Gonzalo Rodriguez Jorge Esquivias Antonio Lafuente Laura Rubio 《Tetrahedron》2006,62(13):3112-3122
Nano conjugated thienylethenyl and thienylethynyl compounds with controlled structure and dimensions have been efficiently prepared, by heterocoupling reaction between 1,4-(thienylethynyl)phenylacetylene (or thienylethenyl)phenylacetylene and 2- or 2,5-dihalothiophene. Conjugated 1,4-di(2-thienylethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiyne were obtained by the homocoupling of the terminal acetylenes in excellent yield. The end-capped (N,N-dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-1-ethynyl]-2,5-di(phenylethynyl)nthiophene were obtained by the heterocoupling between the corresponding terminal acetylene and 2,5-di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)palladium and cuprous iodide system in excellent yield. 相似文献
14.
Zhang-Pei Chen Mu-Wang Chen Lei Shi Chang-Bin Yu Yong-Gui Zhou 《Chemical science》2015,6(6):3415-3419
An efficient palladium-catalyzed asymmetric hydrogenation of fluorinated aromatic pyrazol-5-ols has been developed via capture of the active tautomers. A wide variety of 2,5-disubstituted and 2,4,5-trisubstituted pyrazolidinones have been synthesized with up to 96% and 95% ee, respectively. The hydrogenation pathway includes Brønsted acid promoted tautomerization of pyrazol-5-ols and Pd-catalyzed asymmetric hydrogenation of the active tautomer. 相似文献
15.
Jiri Kos Tomas Gonec Michal Oravec Izabela Jendrzejewska Josef Jampilek 《Molecules (Basel, Switzerland)》2021,26(14)
A set of twenty-four 3-hydroxynaphthalene-2-carboxanilides, disubstituted on the anilide ring by combinations of methoxy/methyl/fluoro/chloro/bromo and ditrifluoromethyl groups at different positions, was prepared. The compounds were tested for their ability to inhibit photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. N-(3,5-Difluorophenyl)-, N-(3,5-dimethylphenyl)-, N-(2,5-difluorophenyl)- and N-(2,5-dimethylphenyl)-3-hydroxynaphthalene-2-carboxamides showed the highest PET-inhibiting activity (IC50 ~ 10 µM) within the series. These compounds were able to inhibit PET in photosystem II. It has been found that PET-inhibiting activity strongly depends on the position of the individual substituents on the anilide ring and on the lipophilicity of the compounds. The electron-withdrawing properties of the substituents contribute towards the PET activity of these compounds. 相似文献
16.
Ahmad Shaabani Afshin Sarvary Sajjad Keshipour Ali Hossein Rezayan Rahim Ghadari 《Tetrahedron》2010,66(10):1911-1914
A new class of pyridinium, quinolinium, isoquinolinum, and N-methylimidazolium-3-(2,5-dihydro-5-oxofuran-3-yl)-4-hydroxyfuran-2(5H)-one salts have been prepared in high yields by reacting pyridine, quinoline, isoquinoline, N-methylimidazole, 1,4-diazabicyclo[2.2.2]octane, and their derivatives with tetronic acid in CH2Cl2. 相似文献
17.
Sheng-Mei Lu 《Journal of organometallic chemistry》2007,692(14):3065-3069
A new catalytic system ([Ru(p-cymene)Cl2]2/I2) has been developed for the hydrogenation of quinoline derivatives with high reactivity. For the 2-methyl-quinoline, the hydrogenation reaction can proceed smoothly at an S/C of 20,000/1 with complete conversion. The iodine additive is important for the reactivity. 相似文献
18.
Dr. Qiang Deng Dr. Rong Zhou Dr. Yong-Chao Zhang Dr. Xiang Li Jiahui Li Prof. Shaobo Tu Prof. Guan Sheng Prof. Jun Wang Prof. Zheling Zeng Dr. Tatchamapan Yoskamtorn Prof. Shik Chi Edman Tsang 《Angewandte Chemie (International ed. in English)》2023,62(9):e202211461
Currently, less favorable C=O hydrogenation and weak concerted acid catalysis cause unsatisfactory catalytic performance in the upgrading of biomass-derived furfurals (i.e., furfural, 5-methyl furfural, and 5-hydroxymethyl furfural) to ketones (i.e., cyclopentanone, 2,5-hexanedione, and 1-hydroxyl-2,5-hexanedione). A series of partially oxidized MAX phase (i.e., Ti3AlC2, Ti2AlC, Ti3SiC2) supporting Pd catalysts were fabricated, which showed high catalytic activity; Pd/Ti3AlC2 in particular displayed high performance for conversion of furfurals into targeted ketones. Detailed studies of the catalytic mechanism confirm that in situ hydrogen spillover generates Frustrated Lewis H+−H− pairs, which not only act as the hydrogenation sites for selective C=O hydrogenation but also provide acid sites for ring opening. The close intimate hydrogenation and acid sites promote bifunctional catalytic reactions, substantially reducing the reported minimum reaction temperature of various furfurals by at least 30–60 °C. 相似文献
19.
《Tetrahedron letters》2004,45(38):7061-7064
End-capped (N,N-dimethylaminophenyl) and 2′-thienylethynyl 2,5-thiophene oligomer structures were synthesized by heterocoupling between the terminal acetylenes such as: p-(N,N-dimethylaminophenyl)ethyne (3) [or 1-(p-(N,N-dimethylaminophenyl)-2-p-(ethynylphenyl)ethyne, 4]; p-(β-ethenyl-2′-thienyl)phenylethyne (E-9) [or p-(β-ethynyl-2′-thienyl)phenylethyne, 11], and 2,5-diiodothiophene, catalyzed by the Cl2Pd(PPh3)2/CuI system, in good to excellent yields. The 2,5-di[(3′,5′-di(trimethylsilylethynyl)phenyl]x-1-ethynyl]thiophene oligomers were prepared by heterocoupling between 3′,5′-di[(trimethylsilylethynyl)phenyl]x-1-ethyne (n = 0-2) terminal acetylenes and 2,5-diiodothiophene, in excellent yields. The terminal acetylenes were efficiently prepared by a specific protection-deprotection methodology. All the ethynylphenyl compounds obtained show fluorescence radiation emission, with a bathochromic shift of the wavelength that increases with the chain conjugation. 相似文献
20.
《Polyhedron》1987,6(6):1329-1335
The preparation and properties of cationic rhodium and iridium complexes of types [M(diolefin)L2](ClO4) and [M(diolefin)L(PPh3)](ClO4) [M = Rh, diolefin = 1,5-cyclooctadiene (COD) or 2,5-norbornadiene; M = Ir, diolefin = COD; L = phosphine sulphide] are described. The complexes have been characterized by IR, 1H NMR and 31P NMR spectroscopy. The use of [M(diolefin)L2](ClO4) as catalyst precursors in homogeneous hydrogenation of olefins has been studied. 相似文献