Kinetics and mechanism of the oxidation of alkyl and aryl methyl ketones by permanganate ion in aqueous ethanoic acid

The kinetics of electron-transfer reactions between permanganate ion and ethyl and aryl methyl ketones have been studied in aqueous MeCO2H acid medium in the presence of HClO4 at different temperatures. For ethyl methyl ketone and XC6H4COMe (X = p-Cl, p-Br or p-NO2) the reaction obeys the rate law –d[MnO4–]/dt = (kKe[H+][MnO4–][RCO Me])/(1 + Ke[H+][RCOMe]).But the oxidations of XC6H4COMe (X = p-Me and p-OMe)follow the rate equation –d[MnO4–]/dt = k3[H+][MnO4–][RCOMe]. The reaction involves a fast pre-equilibrium with intermediate formation of a permanganate ester before the two-electron transfer, rate-determining, step. A number of thermodynamic parameters have been evaluated.     

苯并噻唑 盐催化合成1,4-二羰基化合物

在苯并噻唑 盐和三乙胺存在下, 醛可以作为酰基负离子的合成等价物对α,β-不饱和酮进行Michael加成, 生成相应的1,4-二羰基化合物. 文中对 盐的制备, 催化反应条件及催化反应的机理进行了研究和讨论.     

双高烯丙基硫醚和β,γ-及γ,δ-不饱和缩硫酮的区域专一性碳钯化反应

本工作试图把碳钯化反应发展到双主主烯丙基体系,以考察通过杂原子导向的远端区域专一性的反应以及缩硫酮官能团对硫钯化反应的导向作用.     

Experimental and ab initio structural study of the ketotin compounds,X3SnCR2CH2COMe: crystal structures of X3SnCMe2CH2COMe (X = Cl and I)

The MeCOCH₂CMe₂ ligand in X₃SnCMe₂CH₂COMe ( 2 ; X = halide) acts as a C,O‐chelating group both in the solid state and in non‐coordinating solutions. The intramolecular Sn? O bond lengths in trigonal bipyramidal 2 (X = Cl and I), as determined by X‐ray crystallography, indicate that the stronger interaction occurs in 2 X = Cl. Comparisons with the Sn? O bond lengths in the estertin trihalides, X₃SnCH₂CH₂CO₂R ( 1 ; R = Me), suggest that the latter form stronger chelates than do 2 . In chlorocarbon solution, 2 (X = Cl, I) undergoes exchange reactions, as shown by NMR spectra, to give all possible halide derivatives, ∑(Cl_nI_3?nSnCMe₂CH₂COMe) (n = 0–3). Various ab initio calculations on 2 and X₃SnCH₂CH₂COMe ( 3 ) have been carried out. Comparisons of the theoretical and experimental structures of 2 for X = Cl or I are reported. Copyright © 2005 John Wiley & Sons, Ltd.     

Zur Reaktivität von dinuklearen Platina‐β‐diketonen gegenüber Phosphanen: Diacetylplatin(II)‐Komplexe und mononukleare Platina‐β‐diketone

The Reactivity of Dinuclear Platina‐β‐diketones with Phosphines: Diacetylplatinum(II) Complexes and Mononuclear Platina‐β‐diketones Addition of mono‐ and bidentate phosphines or of AsPh₃ to the platina‐β‐diketone [Pt₂{(COMe)₂H}₂(μ‐Cl)₂] ( 1 ) followed by the addition of NaOMe at ?70 °C resulted in the formation of diacetyl platinum(II) complexes cis‐[Pt(COMe)₂L₂] (L = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; PPh₂(4‐py), 2c ; PMePh₂, 2d ; AsPh₃, 2d ) and [Pt(COMe)₂(L??L)] (L??L = dppe, 3b ; dppp, 3c ), respectively. The analogous reaction with dppm afforded the dinuclear complex cis‐[{Pt(COMe)₂}₂(μ‐dppm)₂] ( 4 ) that reacted in boiling acetone yielding [Pt(COMe)₂(dppm)] ( 3a ). The reactions 1 → 2 / 3 were found to proceed via thermally highly unstable cationic mononuclear platina‐β‐diketone intermediates [Pt{(COMe)₂H}L₂]⁺ and [Pt{(COMe)₂H}(L??L)]⁺, respectively, that could be isolated as chlorides for L??L = dppe ( 5a ) and dppp ( 5b ). The reversibility of the deprotonation of type 5 complexes with NaOMe yielding type 3 complexes was shown by the protonation of the diacetyl complex 3b with HBF₄ yielding the platina‐β‐diketone [Pt{(COMe)₂H}(dppe)](BF₄) ( 5c ). All compounds were fully characterized by means of NMR and IR spectroscopies, and microanalyses. X‐ray diffraction analysis was performed for the complex cis‐[Pt(COMe)₂(PPh₃)₂]·H₂O·CHCl₃ ( 2a ·H₂O·CHCl₃).     

Ortho-hydroxyphenylhydrazo-β-diketones: tautomery, coordination ability, and catalytic activity of their copper(II) complexes toward oxidation of cyclohexane and benzylic alcohols

New hydrazone o-HO-phenylhydrazo-β-diketones (OHADB), R(1)NHN═CR(2)R(3) [R(1) = HO-2-C(6)H(4), R(2) = R(3) = COMe (H(2)L(1), 1), R(2)R(3) = COCH(2)C(Me)(2)CH(2)CO (H(2)L(2), 2), R(2) = COMe, R(3) = COOEt (H(2)L(4), 4); R(1) = HO-2-O(2)N-4-C(6)H(3), R(2)R(3) = COCH(2)C(Me)(2)CH(2)CO (H(2)L(3), 3), R(2) = COMe, R(3) = COOEt (H(2)L(5), 5), R(2)R(3) = COMe (H(2)L(6), 6A)], and their Cu(II) complexes [Cu(2)(CH(3)OH)(2)(μ-L(1))(2)] 7, [Cu(2)(H(2)O)(2)(μ-L(2))(2)] 8, [Cu(H(2)O)(L(3))] 9, [Cu(2)(μ-L(4))(2)](n) 10, [Cu(H(2)O)(L(5))] 11, [Cu(2)(H(2)O)(2)(μ-L(6))(2)] 12A and [Cu(H(2)O)(2)(L(6))] 12B were synthesized and fully characterized, namely, by X-ray analysis (4, 5, 7-12B). Reaction of 6A, Cu(NO(3))(2) and ethylenediamine (en) leads, via Schiff-base condensation, to [Cu{H(2)NCH(2)CH(2)N═C(Me)C(COMe)═NNC(6)H(3)-2-O-4-NO(2)}] (13), and reactions of 12A and 12B with en give the Schiff-base polymer [Cu{H(2)NCH(2)CH(2)N═C(Me)C(COMe)═NNC(6)H(3)-2-O-4-NO(2)}](n) 14. The dependence of the OHADB tautomeric equilibria on temperature, electronic properties of functional groups, and solvent polarity was studied. The OHADB from unsymmetrical β-diketones exist in solution as a mixture of enol-azo and hydrazo tautomeric forms, while in the solid state all the free and coordinated OHADB crystallize in the hydrazo form. The relative stabilities of various tautomers were studied by density functional theory (DFT). 7-14 show catalytic activities for peroxidative oxidation (in MeCN/H(2)O) of cyclohexane to cyclohexanol and cyclohexanone, for selective aerobic oxidation of benzyl alcohols to benzaldehydes in aq. solution, mediated by TEMPO radical, under mild conditions and for the MW-assisted solvent-free synthesis of ketones from secondary alcohols with tert-butylhydroperoxide as oxidant.     

(Sensitized) photolysis of diazonium salts as a mild general method for the generation of aryl cations. Chemoselectivity of the singlet and triplet 4-substituted phenyl cations

The photolysis of a series of 4-X-benzenediazonium tetrafluoroborates is studied in MeCN. Loss of nitrogen occurs from the singlet excited state with X=H, t-Bu, and NMe2 and leads to the singlet aryl cation. This adds to the solvent yielding the corresponding acetanilides. With other substituents, ISC competes with (X=Br, CN) or overcomes (X=COMe, NO2) fragmentation and the aryl cation is formed in part or completely in the triplet state. In neat MeCN, this either abstracts hydrogen from the solvent (in most cases inefficiently) or undergoes intersystem crossing to the more stable singlet that reacts as above. In the presence of pi nucleophiles (allyltrimethylsilane or benzene), the triplet aryl cation is efficiently trapped giving substituted allylbenzenes and biphenyls, respectively. By triplet sensitization by xanthone, the triplet cation and the products from it are obtained from the whole series considered. The direct or sensitized photodecomposition of diazonium fluoroborates, substituted with both electron-donating and -withdrawing substituents, in the presence of alkenes and arenes offers an access to an alternative arylation procedure.     

Migratory insertion in N-heterocyclic carbene-containing Fe carbonyl complexes: an experimental and theoretical study

The compound [Fe(eta-C5H5)(CO)2(Me)] reacts thermally with N-heterocyclic carbenes (L) to give both alkyl, [Fe(eta-C5H5)(L)(CO)(Me)], and acyl, [Fe(eta-C5H5)(L)(CO)(COMe)], derivatives. The reaction temperature has been shown to affect the product distribution. The alkyl and acyl derivatives exist in an equilibrium that is more easily perturbed than in the tertiary phosphine analogues. DFT studies on the reactivity of [Fe(eta-C5H5)(CO)2(Me)] with PH3 and dihydroimidazole-2-ylidene (IH) have shown that CO exchange is energetically favoured for IH, and energetically disfavoured for PH3. The products of CO-induced migratory insertion, [Fe(eta-C5H5)(L)(CO)(COMe)], are more stable than the parent alkyl, [Fe(eta-C5H5)(L)(CO)(Me)], compounds. This stabilisation is larger when L = IH than when L = PH3. Stabilisation of the transition state by agostic interactions was seen in both instances, but this was significantly more pronounced for L = IH.     

DFT studies of the conformational/structural dependencies of geminal 1H,1H scalar coupling 2J(H,H') in substituted methanes

A study is presented of the structural dependencies for scalar, interproton J-coupling across two bonds in a series of substituted methanes. The coupled perturbed, density functional theory method with a B3PW91 functional and aug-cc-pVTZ-J basis sets is used to examine coupling between geminal protons (2)J(H,H') in methane and a series of substituted compounds CH(3)X (X = CH3, CH(2)CH(3), CH=CH2, CH=O, and NH2) as functions of the dihedral angle phi measured about the C1-X2 bonds. All four contributions are obtained but all conformational effects are dominated by the Fermi contact term. Simple linear combination of atomic orbitals (LCAO)-molecular orbital (MO) sum-over-states methods are used to examine the relationships of the coupling constants with dihedral angles as well as internal H-C-H and H-C1-X2 angles. This study explores some novel aspects of geminal H-H coupling including an analysis of the asymmetry in the conformational dependencies arising from non-next-nearest neighbor interactions. For each of the substituted methanes, explicit trigonometric/exponential expressions are given and these accurately reproduce the (2)J(H,H') structural dependencies with standard deviations usually less than 0.03 Hz. The molecular structures for representative bicyclic molecules were fully optimized, and DFT results for (2)J(H,H') reproduce all the trends in the experimental data. A discussion is given on the applicability of the equations for H--H coupling in the substituted methanes to coupling in the bicyclic molecules.     

Complexes of 4‐substituted phenolates with HF and HCN: Energy decomposition and electronic structure analyses of hydrogen bonding

We have computationally studied para‐X‐substituted phenols and phenolates (X = NO, NO₂, CHO, COMe, COOH, CONH₂, Cl, F, H, Me, OMe, and OH) and their hydrogen‐bonded complexes with B^? and HB (B = F and CN), respectively, at B3LYP/6‐311++G** and BLYP‐D/QZ4P levels of theory. Our purpose is to explore the structures and stabilities of these complexes. Moreover, to understand the emerging trends, we have analyzed the bonding mechanisms using the natural bond orbital scheme as well as Kohn–Sham molecular orbital (MO) theory in combination with quantitative energy decomposition analyses [energy decomposition analysis (EDA), extended transition state‐natural orbitals for chemical valence (ETS‐NOCV)]. These quantitative analyses allow for the construction of a simple physical model that explains all computational observations. © 2012 Wiley Periodicals, Inc.     

Studies on the effect of opposite terminal groups in phenylpolyenic conjugative systems

Seven homologous series p-A=B-C₅H₄(CH=CH)_nX=Y (A=B: NO₂, X=Y: CHO, COMe, CN, NO₂; A=B: CN, X=Y: CHO, CN; A=B: H, X=Y: NO₂) were synthesized, the effect of opposite terminal groups in phenylpolyenic conjugative systems has been studied by means of UV, XPS, ¹³C NMR and quantum chemical calculation. The results show that: 1. There exists the effect of opposite terminal groups exists in phenylpolyenic and other aromatic conjugative systems-2. When A=B and X=Y are the same, the group (-X=Y) connected at polyenic chain is a terminal group, while the other is an opposite terminal group. When the two groups are different, the one with weaker conjugative power plays the role of the opposite terminal group. 3. The effect of opposite terminal groups increases successively in the order of CN, COMe, CHO, NO₂ and can be quantitatively described with substitute equivalent ΔNs. The λ_max of compound containing an opposite terminal group can be calculated by the homologous equation 10^?4 $ \tilde v = a + b/(1/2)^2 N'^{- S} a $, most of the calculated values are in agreement with experiment results.     

吲哚并喹嗪衍生物的立体选择性合成

用锂铝氢四还原卟啉得到卟啉醇,它与甲乙酮反应得相应的羟甲基氨基酮,在相转移条件下,它能被转化成光学纯吲哚并喹嗪衍生物.列出了环化机理的反应流程.     

Micellar solubilization: structural and conformational changes investigated by 1H and 13C liquid-state NMR

A combination of (1)H self-diffusion measurements and (13)C chemical shift analysis has been used for the study of the solubilization of amphiphilic additives C(n)H(2n+1)X (n=4, 6; X=OH, NH(2)) in cetyltrimethylammonium bromide (CTAB) micelles. This approach, which could be extended to other mixed systems, allows complementary data on structures of micelles and conformations of alkyl chains to be obtained. Previous results on these systems are confirmed and new features emerge. All the additives studied behave as cosurfactants. Their degree of solubilization is determined solely by their alkyl chain length. In the case of cosurfactants with n=6, polar head group differences have been shown to modify micellar structures. This effect has been linked to differences in cosurfactant penetration into micelles. In parallel, the area of CTAB head groups and the length of cetyl chains gradually decrease on average when solubilizing more cosurfactants. Cetyl chain compression is strong in the case of cosurfactants with n=4, whereas it is slightly compensated by an extension below the micellar surface in the case of longer cosurfactants. These conformational changes are related respectively to the formation of smaller spherical micelles and of anisotropic or swollen micelles.     

Intermolecular interactions in polymorphs of trinuclear gold(I) complexes: insight into the solvoluminescence of Au(I)3(MeN=COMe)3

The trinuclear complex, Au(I)3(MeN=COMe)3, which displays a number of remarkable properties including solvoluminescence, has been found to crystallize as three polymorphs. The new triclinic and monoclinic polymorphs crystallized as colorless blocks, whereas the original hexagonal polymorph formed colorless needles. These polymorphs differ in the manner in which the nearly planar molecules pack and in the nature of the aurophilic interactions between them. Each of the three polymorphs of Au(I)3(MeN=COMe)3 shows a distinctive emission spectrum, but only the original hexagonal polymorph shows the low-energy emission that is responsible for its solvoluminescence. Colorless Au(I)3(n-PentN=COMe)3 crystallized from diethyl ether as needles of an orthorhombic polymorph and blocks of a triclinic polymorph. These polymorphs differ in the orientation of the n-Pent substituents, in the orientation of the trimers with respect to one another, and in the nature of the aurophilic interactions between the molecules. Only the triclinic polymorph of Au(I)3(n-PentN=COMe)3 shows luminescence at room temperature, but it is not solvoluminescent. Colorless Au(I)3(i-PrN=COMe)3 has also been prepared and crystallographically characterized. The isopropyl groups protrude out of the plane of the nine-membered ring and prevent self-association. The closest Au...Au contact between molecules is 6.417 A. Crystalline Au(I)3(i-PrN=COMe)3 is not luminescent at room temperature.     

Cyclopentadienyl ruthenium and osmium complexes : II. The reactivity of π-cyclopentadienyl(triphenylphosphine)-ruthenium(II) and -osmium(II) complexes

Ruthenium and osmium complexes of the type CpMX(PPh₃)L (M = Ru; X = Cl, H, S₂COC₁₀H₁₉, S₂COMe; L & PPh₃ and PHPh₂; M = Os, X = Cl, Br, I, H, D, xanthogenate, dithiocarbamate, BPh₄, L = PPh₃). The compound CpOsCl(PPh₃)₂ is readily soluble in MeOH and in the solution the cation [CpOs(PPh₃)₂]⁺ is present. Upon addition of NaBPh₄ a white compound CpOs(PPh₃)₂BPh₄ immediately precipitates, which can not be solved in MeOH, contrary to the behaviour of the corresponding ruthenium compound.     

How Strong Are Hydrogen Bonds in Metalla‐β‐diketones?

The energies of the kinetically inert, electronically saturated Lukehart-type metalla-beta-diketone [Re{(COMe)2H}(CO)4] (9 a) and of the kinetically labile, electronically unsaturated platina-beta-diketones [Pt{(COMe)2H}Cl2]- (10 a), [Pt2{(COMe)2H}2(micro-Cl)2] (11 a), and [Pt{(COMe)2H}(bpy)]+ (12 a) have been calculated by DFT at the B3LYP/6-311++G(d,p) level using effective core potentials with consideration of relativistic effects for the transition metals. Analogously, energies of the requisite open (non-hydrogen-bonded) equilibrium conformers (9 b, 10 c, 11 b, 12 b) and energies which were obtained from the hydrogen-bonded conformers by rigid rotation of the OH group around the C--O bond by 180 degrees followed by relaxation of all bond lengths and angles (9 c, 10 d, 11 c, 12 d) have been calculated. These energies were found to be higher by 14.7/27.2 (9 b/9 c), 20.7/27.2 (10 c/10 d), 19.2/25.7 (11 b/11 c), and 9.4/19.6 kcal mol(-1) (12 b/12 d) than those of the intramolecularly O--HO hydrogen-bonded metalla-beta-diketones 9 a, 10 a, 11 a, and 12 a, respectively. In acetylacetone (Hacac), the generic organic analogue of metalla-beta-diketones, the energies of the most stable non-hydrogen-bonded enol isomer (6 b) and of the conformer derived from the H-bonded form by rigid rotation of the OH group by 180 degrees followed by subsequent relaxation of all bond lengths and angles (6 k) were found to be 10.9/16.1 kcal mol(-1) (6 b/6 k) higher compared to the intramolecularly O--HO bonded isomer 6 a. Thus, the hydrogen bonds in metalla-beta- diketones must be regarded as strong and were found to be up to twice as strong as that in acetylacetone. A linear relationship was found between the hydrogen-bond energies based on the rigidly rotated structures and the OO separation in the hydrogen-bonded structures. Furthermore, these energies were also found to be correlated with the electron densities at the OH bond critical points (rhobcp) in the O--HO bonds of metalla-beta-diketones 9 a, 10 a, 11 a, and 12 a (calculated using the AIM theory). The comparison of the energies of the doubly intermolecularly hydrogen-bonded dinuclear platina-beta-diketone [{Pt{(COMe)2H}(bpy)}2]2+ (14) with that of the mononuclear intramolecularly hydrogen-bonded cation [Pt{(COMe)2H}(bpy)]+ (12 a) showed that the intermolecular hydrogen bonds in 14 are weaker than the intramolecular hydrogen bond in 12.     

Surface modification by substitution: Changing topology of conformational potential energy surfaces

It is shown for compounds XS-CHCH-CHO that chemical substitution (X = H → F and X = H → Li) results in the change of conformational potential energy surfaces not only in the quantitative but in the qualitative sense as well. Qualitative change always implied a modified surface topology, i.e. critical points are either created by “split-ups” or annihilated by “collapse”. It appears that some kind of “selection rule” might be operative in the “creation” and “annihilation” of critical points during the change of surface topology as the result of chemical substitution.     

35Cl NQR Spectra and ab initio Calculations of gem-Substituted 1-Chlorocyclohexane Derivatives

The ³⁵Cl NQR spectra of gem-substiutted 1-chlorocyclohexane derivatives C₆H₁₀XCl (X = H, CH₃, CH₃O, Cl) at 77 K were measured. Ab initio RHF/6-31G(d) calculations of their conformers, and also of conformers of monosubstituted cyclohexanes were performed. Based on the calculation results, the NQR lines were assigned and the conformational energies of the substituents were evaluated. The relative conformational energies of the Cl atom and CH₃O group disagree with previous data.     

异-α-姜黄烯及其衍生物的合成

姜科姜黄属是一个重要的药用植物群其根茎和块根分别称为姜黄和郁金。中医中药认为, 郁金具有行气, 纠瘀和通经等功效。动物药理试验表明, 姜科植物温郁金具有抗生育活性, 而其挥发油主要含有姜烯、α-姜黄烯和异-α-姜黄烯等倍半萜类化合物。本文合成了温郁金挥发油的另一个成分异-α-姜黄烯和其衍生物2-甲基-6-对甲苯基-2-庚醇、脱氢异-α-姜黄烯和2-甲基-6-对甲苯基-5-庚烯-2-醇。它们的化学结构得到确证。     

四面体手性簇合物CpMo(RCp)WFe(CO)~7(μ~3-S)和CpW(RCp)MoFe(CO)~7 (μ~3- S)的合成及结构表征(R=CO~2Et,COMe,n-Bu)

种用等瓣置换法,通过M^*[(R-Cp)M^1(CO)~3](R=CO~2Et,COMe;M^*=Na;R=n-Bu;M*=Li)与CpM^2FeCo(CO)~8(μ~3-S)反应,得到六种环戊二烯配体含有较大取代基的含硫四面体手性簇合物(R-Cp)M^1CpM^2Fe(CO)~7(μ~3-S)(I-3:M^1=W,M^2=Mo,R=CO~2Et;Ⅱ:M^1=W,M^2=Mo,R=COMe;Ⅲ:M^1=W,M^2=Mo,R=n-Bu;Ⅳ-2:M^1=Mo,M^2=W,R=CO~2Et;Ⅴ:M^1=Mo,M^2=W,R=COMe;Ⅵ:M^1=Mo,M^2=W,R=n-Bu).通过元素分析,IR,1^H/^1^3CNMR对合成的簇合物结要构进行了表征,并讨论了反应途径。