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1.
Concellón JM del Solar V García-Granda S Díaz MR 《The Journal of organic chemistry》2007,72(20):7567-7573
The reaction of chiral (2R,1'S)- or (2S,1'S)-2-(1-aminoalkyl)epoxides 1 or 2 with CO2, generated from acidic treatment of an aqueous solution of NaHCO3 at room temperature, efficiently afforded enantiopure cyclic carbonates 3 or 4, respectively, with total selectivity. Compounds 3 and 4 were readily transformed into the corresponding diols 7 and 8 by reaction with LiAlH4 or by basic hydrolysis. When compounds 3 or 4 were allowed to react with methyllithium at -78 degrees C, O1-acetylalkane-1,2-diols 9 and 10 were obtained with total or high selectivity. 相似文献
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The title reaction, which is spin‐forbidden for N2(X1∑) + NO(X2Π) production, has been studied from 960 to 1130 K in a high‐temperature photochemistry reactor. No reaction could be observed, indicating k < 1 × 10?15 cm3 molecule?1 s?1. It is concluded that there is no significant contribution from the spin‐allowed exothermic path leading to N2(X1∑) + NO(a4Π). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 387–389, 2001 相似文献
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Avenoza A Busto JH Jiménez-Osés G Peregrina JM 《The Journal of organic chemistry》2006,71(4):1692-1695
The work described here demonstrates that the five-membered cyclic alpha-methylisoserine-derived sulfamidate, (R)-1, behaves as an excellent chiral building block for the ring-opening reaction by S(N)2 attack with sulfur nucleophiles at the quaternary carbon. As a synthetic application of this methodology, and to show that this sulfamidate is a valuable starting material, the synthesis of two new alpha-methylisocysteine derivatives has been carried out to cover the lack of alpha- and beta-methylated amino acids that incorporate the cysteine or isocysteine skeleton. These compounds are two new alpha,alpha-disubstituted beta-amino acids (beta(2,2)-amino acids), and the synthetic routes involve nucleophilic ring opening followed by acid hydrolysis. 相似文献
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《Tetrahedron: Asymmetry》2001,12(19):2649-2655
Pd(0)-catalyzed allylic amination of 3-bromocyclohexene with (1S,2S)-2-amino-1,2-diphenylethanol and subsequent intramolecular oxyselenenylation of the resulting allylic amine 6 followed by oxidation–elimination afforded the valuable cis-fused bicyclic olefin 10. Oxyselenenylation of cyclohexene with (1S,2S)-N-(benzyloxycarbonyl)-2-amino-1,2-diphenylethanol and subsequent oxidation–elimination gave the allylic ether 18. Intramolecular aminoselenenylation of 18 followed by oxidation–elimination provided the cis-fused bicyclic olefin 21, which is the regioisomer of 10. Further stereoselective transformation of 10 afforded enantiopure aminocyclohexitols. 相似文献
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《Tetrahedron: Asymmetry》2003,14(8):1063-1072
An efficient and easy one-pot reaction from readily available racemic 2-substituted cyclobutanones gave, by means of asymmetric Strecker synthesis in the presence of an amine chiral auxiliary, two major aminonitriles with excellent diastereoselectivity. After separation, the major cis-aminonitriles were hydrolysed and hydrogenolysed to lead for the first time to pure non-racemic (+)-1-amino-2-isopropylcyclobutanecarboxylic acid (ACBC) and its antipode. 相似文献
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《Tetrahedron: Asymmetry》2007,18(18):2218-2226
The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis. 相似文献
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Ming‐Hui Zuo Hui‐Ling Liu Xu‐Ri Huang Jin‐Hui Zhan Chia‐Chung Sun 《International journal of quantum chemistry》2008,108(8):1309-1315
The reaction of N (2D) radical with NO2 molecule has been studied theoretically using density functional theory and ab initio quantum chemistry method. Singlet electronic state [N2O2] potential energy surfaces (PES) are calculated at the CCSD(T)/aug‐cc‐pVDZ//B3LYP/6‐311+G(d) + ZPE and G3B3 levels of theory. All the involved transition states for generation of (2NO) and (O2 + N2) lie much lower than the reactants. Thus, the novel reaction N + NO2 can proceed effectively even at low temperatures and it is expected to play a role in both combustion and interstellar processes. On the basis of the analysis of the kinetics of all pathways through which the reactions proceed, we expect that the competitive power of reaction pathways may vary with experimental conditions for the title reaction. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
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Bis(N2-hydroxyhexafluoroisopropyl-N1,N1-substituted) terephthalamidines, which are stable up to their melting points, were obtained by reacting substituted tetraphthalamidines with hexafluoroacetone. The reaction of bis(N2-hydroxyhexafluoroisopropyl-N1N1-substituted)terephthalamidines with perfluorohexanecarbonitrile results in the formation of 1,4-bis(2,4-per-fluorohexyltriazinyl) benzene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1613–1616, July, 1990. 相似文献
10.
Jenkins RM Pinder TA Hatley ML Reibenspies JH Darensbourg MY 《Inorganic chemistry》2011,50(5):1849-1855
The versatile N(2)S(2) tetradentate ligands (bme-daco)(2-), (bme-dach)(2-), and (ema)(4-) are known to accommodate many divalent transition-metal ions (M = Ni(II), Pd(II), Pt(II), Pb(II), Zn(II), Cd(II), Cu(II), and Fe(II)) while maintaining reactivity at the S-thiolate sites of the respective N(2)S(2)M complexes. The vanadyl ion, of interest for its pharmacological possibilities and its spin-label reporter properties for bioinorganic studies, also shows an affinity for such mixed nitrogen/sulfur-donor environments. Thus, (V≡O)(2+) analogues of a well-characterized series of N(2)S(2)Ni complexes have been prepared as mimics of possible N(2)S(2)(V≡O) formed from in vivo binding sites of the tripeptide motif, Cys-X-Cys. The nucleophilicity of the S-thiolate in these systems is explored with alkylating agents. IR [ν(VO)], electronic spectral, and electron paramagnetic resonance measurements are presented. X-ray diffraction studies of (bme-daco)(V≡O), (bme-dach)(V≡O), and [Et(4)N](2)[(ema)(V≡O)] further characterize the vanadyl complexes. A comparison of the spectral properties with the product of vanadyl interaction with the CGC tripeptide, the biological analogue of the tetraanionic N(2)S(2) ligand, is given. 相似文献
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[reaction: see text] The intramolecular in-plane S(N)2 type reaction of haloalkene E-8a was predicted to be a facile process for the first time by DFT calculations (B3LYP/6-31+G(d),SCRF(dipole, solvent = DMF)) (DeltaG = 14.4 kcal/mol). The prediction was confirmed experimentally. When E-8a was treated with NaH in DMF, benzofuran was obtained in 95% yield. On the other hand, Z-8a was recovered quantitatively even after heating at 110 degrees C. 相似文献
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Stephen G. Davies Ai M. Fletcher Matthew E. Peters Paul M. Roberts James E. Thomson 《Tetrahedron》2019,75(49):130713
The key step in our synthetic strategy towards (S,S)-methylphenidate hydrochloride employs the ring-opening of an in situ formed aziridinium intermediate. Treatment of an α-hydroxy-β-amino ester with methanesulfonic anhydride promoted aziridinium formation and the subsequent addition of phenylmagnesium bromide resulted in stereospecific and regioselective ring-opening to give the corresponding α-phenyl-β-amino ester with overall retention of configuration. Subsequent functional group manipulation followed by N-deprotection and cyclisation generated the piperidine ring within the target compound, and transesterification gave (S,S)-methylphenidate hydrochloride, in only 8 steps from 1,5-pentanediol, in 15% overall yield. These results demonstrate the synthetic utility of enantiopure aziridinium intermediates as substrates for the generation of stereodefined C–C bonds, and crucially this methodology provides access to α-substituted-β-amino ester substrates that are not accessible via enolate alkylation chemistry. The strategy reported herein is potentially applicable to all possible stereoisomers of methylphenidate as well as differentially substituted analogues. 相似文献
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[reaction: see text] A diradical-promoted (n + 2 - 1) ring expansion reaction based on vinyl side chain insertion (+2C) and decarbonylation (-1C) has been developed. Flash vacuum pyrolysis (FVP) of medium- and large-ring 2-trimethylsilyloxy-2-vinyl-cycloalkanones at 500-600 degrees C affords the one-carbon ring-expanded cycloalkanones in good yields. Methyl groups on the vinyl moiety are transformed regiospecifically as corresponding alpha- and beta-substituents, respectively. 2-Ethynyl precursor analogues react in a manner similar to give alpha,beta-unsaturated cyclic ketones. 相似文献
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Rebecca McClain Christos D. Malliakas Jiahong Shen Jiangang He Chris Wolverton Gabriela B. Gonzlez Mercouri G. Kanatzidis 《Chemical science》2021,12(4):1378
Solid-state synthesis has historically focused on reactants and end products; however, knowledge of reaction pathways, intermediate phases and their formation may provide mechanistic insight of solid-state reactions. With an increased understanding of reaction progressions, design principles can be deduced, affording more predictive power in materials synthesis. In pursuit of this goal, in situ powder X-ray diffraction is employed to observe crystalline phase evolution over the course of the reaction, thereby constructing a “panoramic” view of the reaction from beginning to end. We conducted in situ diffraction studies in the K–Bi–Q (Q = S, Se) system to understand the formation of phases occurring in this system in the course of their reactions. Powder mixtures of K2Q to Bi2Q3 in 1 : 1 and 1.5 : 1 ratios were heated to 800 °C or 650 °C, while simultaneously collecting diffraction data. Three new phases, K3BiS3, β-KBiS2, and β-KBiSe2, were discovered. Panoramic synthesis showed that K3BiQ3 serves an important mechanistic role as a structural intermediate in both chalcogen systems (Q = S, Se) in the path to form the KBiQ2 structure. Thermal analysis and calculations at the density functional theory (DFT) level show that the cation-ordered β-KBiQ2 polymorphs are the thermodynamically stable phase in this compositional space, while Pair Distribution Function (PDF) analysis shows that all α-KBiQ2 structures have local disorder due to stereochemically active lone pair expression of the bismuth atoms. The formation of the β-KBiQ2 structures, both of which crystallize in the α-NaFeO2 structure type, show a boundary where the structure can be disordered or ordered with regards to the alkali metal and bismuth. A cation radius tolerance for six-coordinate cation site sharing of ∼ 1.3 is proposed. The mechanistic insight the panoramic synthesis technique provides in the K–Bi–Q system is progress towards the overarching goal of synthesis-by-design.This work uses in situ powder X-ray diffraction studies to observe crystalline phase evolution over the course of multiple K-Bi-Q (Q = S, Se) reactions, thereby constructing a “panoramic” view of each reaction from beginning to end. 相似文献
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trans-Cumylcyclohexanol (TCC) is used as a chiral auxiliary for the stereoselective addition of tributyltinlithium to N-acylpyrrolidinium/piperidinium ion with 70-80% diastereoselectivity at 0 °C. After removal of the minor diastereomer by radial chromatography, enantiopure N-methyl-2-(tributylstannyl)pyrrolidine and piperidine were produced by reductive removal of the auxiliary. 相似文献
17.
《Chemical physics letters》1987,134(4):341-346
The rate constant for the reaction of ground state zinc atoms with nitrous oxide at 303 K was determined to be (1.8 ± 0.5)×10−15 cm3 molecule−1 s−1 at pressures of ≈ 10 Torr. In contrast to a previous experiment, no chemiluminescent products were observed. The result, discussed in terms of an ionic intermediate mechanism and recent ZnO electronic structure calculations, is shown to be consistent with the surface crossing model even though the rate constant is orders of magnitude less than those typically used to invoke the model. 相似文献
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Natalia A. Kopylova Oleksandr O. Grygorenko Igor V. Komarov Ulrich Groth 《Tetrahedron: Asymmetry》2010,21(23):2868-2871
A novel approach to the synthesis of an enantiopure bicyclic proline analogue, hexahydrocyclopenta[b]pyrrole-6a(1H)-carboxylic acid (‘2,3-propanoproline’), has been developed. The method relied on tandem Strecker-nucleophilic cyclization reaction of 2-(2-bromoethyl)cyclopentanone. The overall synthetic scheme included six steps and resulted in 18% overall yield of both enantiomers of the title amino acid. 相似文献
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《Polyhedron》1987,6(5):939-941
The utility of metal atom vapour synthesis in the preparation of metalla-sulphur-nitrogen compounds has been investigated. Reaction of nickel atoms with disulphurdinitride, S2N2, gave, after extraction with methanol, Ni(S2N2H)2 in ca 15% yield. 相似文献