Density functional study of S(N) 2 substitution reactions for CH(3) Cl + CX(1) X(2•-) (X(1) X(2) = HH, HF, HCl, HBr, HI, FF, ClCl, BrBr, and II)

A systematic investigation on the S_N2 displacement reactions of nine carbene radical anions toward the substrate CH₃Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6‐31+G (d, p)/relativistic effective core potential (RECP), 6‐311++G (d, p)/RECP, and aug‐cc‐pVTZ/RECP. The studied models are CX¹X^2?? + CH₃Cl → X²X¹CH₃C^? + Cl^?, with CX¹X^2?? = CH₂^??, CHF^??, CHCl^??, CHBr^??, CHI^??, CF₂^??, CCl₂^??, CBr₂^??, and CI₂^??. The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH₂^?? should be a strongest base among the anion‐containing species (CX¹X^2??) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the S_N2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back‐S_N2 pathway is much more preferred than the front‐S_N2 one in terms of the energy gaps [ΔE(front)?ΔE(back)], steric demand, NBO population analysis. Thus, the back‐S_N2 reaction was discussed in detail. On the one hand, based on the energy barriers (ΔE and ΔE) analysis, we have strongly affirmed that the stabilization of back attacking transition states (b‐TSs) presents increase in the order: b‐TS‐CI₂ < b‐TS‐CBr₂ < b‐TS‐CCl₂ < b‐TS‐CHI < b‐TS‐CHBr < b‐TS‐CHCl < b‐TS‐CF₂ < b‐TS‐CHF < b‐TS‐CH₂. On the other hand, depended on discussions of the correlations of ΔE with influence factors (PA, IE, bond order, and ΔE), we have explored how and to what extent they affect the reactions. Moreover, we have predicted that the less size of substitution (α‐atom) required for the gas‐phase reaction with α‐nucleophile is related to the α‐effect and estimated that the reaction with the stronger PA nucleophile, holding the lighter substituted atom, corresponds to the greater exothermicity given out from reactants to products. © 2012 Wiley Periodicals, Inc. J Comput Chem, 2012     

Crystal Structure of 1, 1-Dichloro-la, 3-diphenyl-1, la, 2, 3-tetrahydro-azirino [2, 1-d ] [1, 5]benzothiazepine (C_(22),H_(17)Cl_2NS )

1INTR0DUCTI0NBenzoheteroazepinecompoundsareimportantpharmaceuticalagents"-".Inre-centyears,ithasbeenfoundthatbenzoheter0azepinetricyclicderivatives,especiallythosefusedwithotherfiveorsix-memberedheterocycle,area1soofpotentialphar-maceuticalinterestst4-6j.Hence,muchattentionhasbeenpaidtothesynthesesofthem,suchasl,3-oxazino[3,2-djt1,5jbenzothia/diazepin-l-onet"'J,1,2,4-tria-zolo[4,3-dj[1,5jbenzothia/diazepine"',1,2,4-oxadiazolo[4,5-dj[l,5jbenzothia/diazepine',',andsoon.Meanwhiletheirstructur…     

Excited-state dynamics of trans,trans-1,3,5,7-octatetraene: estimation of decay rate constants of 1(1)B(u) ⇝ 2(1)A(g) and 2(1)A(g) ⇝ 1(1)A(g) internal conversions

The general expressions we previously derived for calculating internal conversion rate constants between two adiabatic displaced-distorted-rotated potential energy surfaces, by including all vibratinal modes, are applied to estimate the decay rate constants of 1(1)B(u) ? 2(1)A(g) and 2(1)A(g) ? 1(1)A(g) internal conversions in trans,trans-1,3,5,7-octatetraene molecule. The minimal models with respect to the number and types of vibrational modes are determined for these processes. Our calculations show that in the low temperature limit the 1(1)B(u) ? 2(1)A(g) internal conversion takes place on a 232-290 fs time scale in the condensed phase and 2 ps in the gas phase, whereas 2(1)A(g) ? 1(1)A(g) internal conversion takes place on a 2 μs time scale under the isolated conditions.     

Synthesis and cytotoxicity of dinuclear platinum(Ⅱ) complexes of (1S, 3S)-1, 2, 3, 4-tetrahydroisoquinolines

A series of novel dinuclear platinum(Ⅱ) complexes with (1S, 3S)-1,2,3,4-tetrahydroisoquinolines as the ligands were synthesized as potential anticancer agents in several steps starting from commercially available L-DOPA. The cytotoxicities of the series of dinuclear platinum(Ⅱ) complexes of tetrahydroisoquinoline were tested against HCT-8, BEL-7402, A2780, MCF-7, Hela, A549 and BGC-823 cell lines by the MTT test. These complexes showed selective inhibition activity against cisplatin-insensitive cell line Skov3.     

Synthesis and characterization of a 2, 5-Bis(trimethylsilyl)-substituted Bis(1, 1′-silolide) dianion

A novel silyl-substituted bis(1, 1′-silolide) dianion has been isolated and characterized by single-crystal X-ray analysis for the first time. The ¹H, ²⁹Si, and ¹³C NMR spectra show significant delocalization of the negative charges to the silole ring. X-ray crystallography revealed equalized C?C distances and DFT calculation also indicates for significant aromaticity. Reaction with trimethylchlorosilane gave the expected bis(1, 2, 5-tris(trimethylsilyl)-3, 4-diphenyl-silacyclopentadienyl).     

THE POLYMERIC COMPLEX 1, 10-PHENANTHROLINE-N,N'-(μ-NICOTINATO-N,O)DIAQUACOPPER(II) NITRATE DIHYDRATE

Abstract

The title complex has been prepared and its structure determined by X-ray diffraction methods. The complex crystallizes space group P2₁/a with a = 12.833(3), b = 10.443(2), c = 16.628(2)Å, β = 111.686(9)°. The nicotinate anions bridge adjacent Cu(II) atoms through both the pyridine N atom and the carboxyl O atom to form zigzag polymeric chains along the b axis. The carboxyl group of the nicotinate anion coordinates to the Cu(II) atom as a unidentate. Based on the molecular structure the infrared spectrum is discussed.     

Synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones

A synthesis of the enamine (−)-(1′S)-5-ethyl-1-(1′-phenylethyl)-1,2,3,4-tetrahydropyridine 4 and its application in a synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones 5 and 6 is described. In addition, an X-ray study of 6 is reported. Finally, the preparation of (+)-(4aS,8aR)-4a-ethyl-octahydroquinolin-7-one 7 is described.     

Ir(CO)Cla(Ph2Ppy)2HgClb(HgCl2)c (a,b=1, 2, c=0, 1)的Ir-Hg相互作用和氧化还原反应性质

应用密度泛函理论(DFT)的PBE0方法, 金属原子采用SDD基组, H、C、O和N原子采用6-31G*基组, P和Cl原子采用6-311G*基组, 对单核配合物Ir(CO)Cl(Ph2Ppy)2(1), 双核配合物Ir(CO)(Cl)2(Ph2Ppy)2HgCl(2)、Ir(CO)Cl(Ph2Ppy)2HgCl2(3)和Ir(CO)(Cl)2(HgCl2)(Ph2Ppy)2HgCl(4)进行结构优化, 并在优化的基础上采用基组重叠误差(BSSE)校正计算相互作用能, 通过自然键轨道(NBO)和前线轨道分析研究Ir-Hg相互作用和氧化还原反应的实质. 通过计算发现, Ir(CO)Cl(Ph2Ppy)2与HgCl2发生氧化还原反应得到的产物2和4比非氧化还原产物3稳定. Ir-Hg相互作用强度顺序为3<4<2, 且随着Ir-Hg相互作用强度增大, HOMO轨道中Ir和Hg成分逐渐趋于接近. 配合物2和4都具有一对Ir-Hg成键与反键轨道, 其成键轨道的组成分别为0.5985sd0.06Hg+0.8012sd2.48Ir和0.5794sd0.05Hg+0.8151sd2.48Ir, 但3中Ir与Hg的相互作用较弱, 只存在弱相互作用(电荷转移作用), 表现为nIr→nHg的直接作用和σIr—P(1)→nHg、σIr—C(1)→nHg的间接作用.     

CRYSTAL AND MOLECULAR STRUCTURE OF 3a-(4-CHLORO-PHENYL)-1, 5-DIPHENYL-3a, 4,5,11-TETRAHYDRO-1, 2, 4-OXA-DIAZOLINO [5,4-d][1, 5]BENZOTHIAZEPINE, (C_(28)H_(21)N_2OClS)

<正> The structure of 3a-(4-chlorophenyl)-1, 5-diphenyl-3a, 4,5,11-te-trahydrq-1, 2, 4-oxadiazolino [5, 4-d][1, 5] benzothiazepine (C28H21N2OClS) has been determined. The compound crystallizes in triclinic space group P1 with two formula units in a cell of dimensions: a =11. 114(2), b = 11. 673(1), c=10. 435(1) (?), α=98. 42(1), β=118. 69(1),γ = 98. 64(1)° and V = 1136. 2(3)(?)3. The structure was solved by using direct methods and refined by full matrix least-squares. The final crystallographic discrepancy factor is 0. 058 for 2384 observed reflections. The molecular backbone is a tricyclic system : The seven-membered hetero ring in the center is in twisted-boat conformation, and is cis-fused to 1, 2, 4-oxadiazolino ring which is in an envelope form, together with the equilaterally adjoined benzene ring . The compound has a non-planar conjugation system.     

THE POLYMERIC COPPER(II) COMPLEX 1, 10-PHENANTHROLINE -N,N '-(μ-ISONICOTINATO-N,O) MONOAQUACOPPER(II) NITRATE DIHYDRATE

Abstract

The title complex has been prepared and its structure determined by X-ray diffraction. The complex crystallizes in space group C2/c with a = 26.892(5), b = 10.479(4), c = 14.179(2) Å, β = 98.59(2)°. Isonicotinate anions bridge adjacent Cu(II) atoms through the pyridine N atom and the carboxyl O atom to form zigzag polymeric chains along the b axis. The carboxyl group of the isonicotinate anion coordinates to the Cu(II) atom as a unidentate. Based on the molecular structure the infrared spectrum is discussed.     

Das papierchromatographische Verhalten von 1-?thinyl-cyclohexyl-carbaminat (Valamin, Va) und 1-?thinyl-eyclohexyl-allophanat (Dolcentol, Do)

Ohne Zusammenfassung     

Facile Syntheses of (±)-Curcuphenol, (±)-Curcudiol, (±)-Curcuhydroquinone,and (±)-Curcuquinone

The syntheses of (±)-curcuphenol 1, (±)-curcudiol 2, (±)-curcuhydroquinone 3, and (±)-curcuquinone 4 have been achieved. The key steps involved in the syntheses were the Reformatsky reaction and hydrogenation reaction.     

Synthesis,Crystal Structure,and Cytotoxic Property of Di(μ1’’,1’’-azide)bis(4-nitro-2-(3'-dimethylamino- n-propylimino)methylenephenolate)dizinc(Ⅱ)

The title azide-bridged dinuclear Schiff base zinc(II) complex [Zn2(C12H16N3O3)2- (μ1,1-N3)2] was prepared and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/n with a = 8.736(2), b = 14.850(3), c = 11.775(2) , β = 102.42(3)o, V = 1491.8(5) 3, Z = 2, Dc = 1.593 g/cm3, Mr = 715.36, λ(MoKα) = 0.71073 , μ = 1.669 mm-1, F(000) = 736, the final R = 0.0338 and wR = 0.0789. A total of 3411 unique reflections were collected, of which 2777 with I > 2σ(I) were observed. The molecule of the complex is located on a crystallographic inversion centre. Each Zn atom in the complex is five-coordinated by one Schiff base ligand and two bridging azide groups, forming a trigonal bipyramidal configuration. The Zn···Zn distance is 3.328(2) . In the crystal structure, molecules are linked through intermolecular C–H···N hydrogen bonds, forming layers parallel to the bc plane. The complex shows low cytotoxic property to both normal and carcinoma cells.     

DiastereoselectiveandEnantioselectiveSynthesisof(1S,2S)-2-Ethyl-1-aminocyclopropaneCarboxylicAcid

During the last decade, 1-aminocyclopropanecarboxylic acid and its derivatives (ACCS) have attracted increasing attention of organic and bioorganic chemists due to their outstanding biological properties, ranging from antimicrobial, insecticidal, plant growth and fruit ripening controls, etc.1. Moreover, the three-membered carbocycle provides building blocks of unprecedented synthetic potential because it undergoes selective ring opening, ring enlargement or cycloaddition reactions2. The mo…     

Unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1-phenylethyl)octahydroquinolin-7-ones

An unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)-and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)octahydroquinolin-7-ones 1 and 2 is described. In addition, a diastereospecific intramolecular Michael reaction of 3·HCl and 4·HCl is reported.     

Spectroscopic analysis of the coupled 1(1)Π, 2(3)Σ+ (Ω = 0-, 1), and b(3)Π (Ω = 0±, 1, 2) states of the KRb molecule using both ultracold molecules and molecular beam experiments

We report the spectroscopic characterization of excited electronic states of KRb by combining spectra from molecular beam (MB) experiments with those from ultracold molecules (UM) formed by photoassociation (PA) of ultracold atoms. Spectra involving the 1(1)Π, 2(3)Σ(+), and b(3)Π states in a strongly perturbed region have been identified. This approach provides a powerful method to identify the vibrational levels of the excited electronic states perturbed globally by neighboring electronic states. This is because the two sets of spectra from the UM and the MB experiments probe the same energy region from very different initial electronic states. The UM experiments utilize high v' levels of the a(3)Σ(+) state with large internuclear separations, while the MB experiments utilize low v' levels of the ground X(1)Σ(+) state with near-equilibrium internuclear separations. Only the Ω = 1 levels of the 2(3)Σ(+) and b(3)Π states are observed in the MB spectra, while the Ω = 0(-), 1 levels of the 2(3)Σ(+) state and the Ω = 0(±), 1, 2 levels of the b(3)Π state are observed in the UM spectra.     

Extraction,Separation and Spectrophotometric Determination of Bismuth(III) Using 1(4′-Bromophenyl) 4,4,6-Trimethyl (1H,4H)-Pyrimidine-2-Thiol

Abstract

The operating conditions for the spectrophotometric determination of bismuth(III) with 1-(4′-bromophenyl)-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (4′bromo PTPT) as a ligand by a liquid-liquid extraction technique are presented. In acidic conditions bismuth(III) forms a yellow complex with the ligand which can be extracted in chloroform with an absorption maxima at 410 nm. The molar absorptivity is 1.5×10⁴ l mole^?1 cm^?1 and Sandell's sensitivity is 14.3 ng cm^?2. The difference in the absorbance between the chloroform blank and bismuth(III) sample increases linearly in the concentration range 2-14 ppm at 0.3 M hydrochloric acid. The proposed method is extremely sensitive, rapid, reproducible and has been satisfactorily applied to the determination of trace amounts of bismuth(III) in synthetic mixtures, alloys and pharmaceutical formulations and also provides binary separation of bismuth(III) from selenium, tellurium, lead, antimony, copper and gold. The overall process of extraction and determination takes about 15 to 20 min.     

Methylenecyclohexane annulation. Total synthesis of (±)-axamide-1, (±)-axisonitrile-1, and the corresponding C-10 epimers

Conjugate addition of 2-(5-chloro-1-pentenyl)magnesium bromide (12) to 2-methyl-2-cyclopenten-1-one (6), followed by intramolecular alkylation of the resultant product, afforded (85%) the bicyclic ketone 7, which was transformed (77%) into the enone 16. Titanium tetrachloride-catalyzed conjugate addition of 3-methyl-1,1-bis(trimethylsiloxy)-1-butene to 16 gave (93%) a 3:2 mixture of the keto acids 20 and 21, which were separated. Compound 20, the stereochemistry of which was confirmed by a single-crystal X-ray analysis, was converted into (±)-axamide-1 (1) and (±)-axisonitrile-1 (2), while 21 was transformed into the corresponding C-10 epimers 8 and 9, respectively.     

Structure,microstructure and microhardness of rapidly solidified Smy(FexNi1-x)4Sb12 (x = 0.45, 0.50, 0.70, 1) thermoelectric compounds

Skutterudites are interesting compounds for thermoelectric applications. The main drawback in the synthesis of skutterudites by solidification of the melt is the occurrence of two peritectic reactions requiring long annealing times to form a single phase. Aim of this work is to investigate an alternative route for synthesis, based on rapid solidification by planar flow casting. The effect of cooling rate on phases formation and composition, as well as on structure, microstructure and mechanical properties of the filled Sm_y(Fe_xNi_1-x)₄Sb₁₂ (x = 0.45, 0.50, 0.70, 1) skutterudites was studied. Conversely to slowly cooled ingots, rapidly quenched ribbons show skutterudite as the main phase, suggesting that deep undercooling of the liquid prevents the nucleation of high temperature phases, such as (Fe,Ni)Sb and (Fe,Ni)Sb₂. In as-quenched samples, a slightly out of equilibrium Sm content is revealed, which does not alter the position of the p/n boundary; nevertheless, it exerts an influence on crystallographic properties, such as the cell parameter and the shape of the Sb₄ rings in the structure. As-quenched ribbons show a fine microstructure of the skutterudite phase (grain size of 2–20 μm), which only moderately coarsens after annealing at 873 K for 4 days. Vickers microhardness values (350–400 HV) of the skutterudite phase in as-quenched ribbons are affected by the presence of softer phases (i.e. Sb), which are homogeneously and finely dispersed within the sample. The skutterudite hardens after annealing as a consequence of a moderate grain growth, which limits the matrix effect due to the presence of additional phases.     

Chemoenzymatic synthesis of 1α,24(R)-dihydroxycholesterol

1α,24(R)-Dihydroxycholesterol, which is the key intermediate for the synthesis of 1α,24(R)-dihydroxyvitamin D₃, was effectively synthesized via stereoselective esterification of the 24(R)-hydroxy group using a lipase in combination with inversion of configuration of the 24(S)-hydroxy group using the Mitsunobu reaction (R:S=99:1).