Reactions of 1,4-difluoro-2,5-dimethoxybenzene with LDA (1:2) at low temperatures generated organodilithio intermediates; quenching the reaction mixtures with chlorophosphines ClPR2 produced 1,4-bis(phosphino)-2,5-difluoro-3,6-dimethoxybenzenes 1a (R = Ph) and 1b (R = iPr). Demethylation of 1a–b was accomplished by BBr3, yielding bis(phosphino)hydroquinones 2a–b. Treating 2a–b with excess hydrogen peroxide produced bis(phosphinyl)hydroquinones 3a–b. The binucleating properties of 2a were established by the formation of a bimetallic nickel complex upon reaction with Ph2Ni(PMe3)2. Electrochemical activity of hydroquinones 2a–b and 3a–b was examined by cyclic voltammetry. In addition, compounds 2a, 3a and 3b were obtained in crystalline form and characterized by single-crystal X-ray diffraction. The influence of the fluorine substituents on the composition of the frontier orbitals of 2a and 3a was examined by computational methods. 相似文献
Photocatalysis of biscarbonylrhenium complexes cis,trans-[Re(dmbpy)(CO)2(PR3) (PR′3)]+ (dmbpy=4,4′-dimethyl-2,2′-bipyridine: R, R′=Ph (1a+); p-FPh (1b+); R=Ph, R′=OEt (1c+); R, R′=O-i-Pr (1d+)) is reported for the first time. The rhenium complexes with two triarylphosphine ligands (1a+, 1b+) efficiently photocatalyzed CO2 reduction with triethanolamine as a sacrificial donor. On the other hand, the complexes with one or two trialkylphosphite ligand(s) (1c+, 1d+) had low photocatalytic abilities under the same reaction conditions. 相似文献
Dimethyldioxirane (1a) and its trifluoro analog (1b) were employed to achieve selectively the direct transformation of hex-3-yne-2,5-diol 3a and 1,4-diphenyl-but-2yne-1,4-diol 3b (two representative acetylenic 1,4-diols) into the corresponding carbonyls, leaving the carbon-carbon triple bond moiety untouched. The results are compared with those recorded in the analogous oxidation using the methyltrioxorhenium (MTO)/85% H2O2 homogeneous system. The powerful methyl(trifluoromethyl)dioxirane (1b) is the reagent of choice to achieve optimum yields of the target alkyne-1,4-diones, which are extremely versatile synthons. 相似文献
Butane-2,3- (1a), pentane-2,4- (1b) and hexane-2,5-dione (1c) react with Bu2(CH2=CHCH2)SnCl in the presence of water to give monoallylated keto-ols (2a, 2b) and/or diallylated diols (3a, 3b, 3c), this depending upon the employed molar ratio [diketone]/[allyltin chloride]. Bu(CH2=CHCH2)SnCl2 reacts with neat 1c in a one-pot synthesis to give mixtures of heterocyclic compounds: 2,5-diallyl-2,5-dimethyltetrahydrofuran (4), and 3-chloro-1,5-dimethyl-8-oxabicyclo [3,2,1] octane (5). Compound 4 is also obtained in high yield from the corresponding diol 3c by cyclodehydration promoted by RSnCl3 (R = Me and Bu). 相似文献
A mixture of 1a+1b (17α), obtained by C-17-epimerization of pregnenolone (1a) was converted into 3a+3b by Wittig-reaction. 3a+3b were acetylated to a mixture of 4a+4b, from which 4b was isolated by cristallization of 3a and following AgNO3-chromatography of the mother-liquors. Δ20(22) → Δ17-doublebond-isomerization occurs by hydrogenation (Pd/C) of 3a (17β) to give 5. Hydrogenation (Pt-catalyst) of 4b (17α) leads to 8b, which was converted into the 20-methylpregnane-derivatives 7b, 9b–13b. By comparison with the 17β epimers 1a–4a, 7a–13a a spectroscopic determination of the relative configuration on C-17 of 17-alkylsubstituted steroids was possible. 相似文献
Addition of BH3·thf to 1-alkylimidazoles (alkyl=methyl, butyl) and 1-methylbenzimidazole leads to BH3 adducts, which are deprotonated by BuLi to yield the organolithium compounds (L)Li+(1b–d)−. In the solid state (thf)Li+1b− is dimeric. The acyl–iron complexes (thf)3Li+(3b,d)− are formed from (thf)Li+(1b,d)− and Fe(CO)5. (L)Li+(1a–c)− react with [CpFe(CO)2X], however, the only complex obtained is [CpFe(CO)21a] (5a). The analogous reaction of (L)Li+1a− with the pentadienyl complex [(C7H11)Fe(CO)2Br] yields the corresponding iron compound 6a. Their compositions follow from spectroscopic data. Treatment of Cp2TiCl with (L)Li+1a− leads to [Cp2Ti1a] (7a), which could not be oxidized with PbCl2 to give the corresponding Ti(IV) complex. The compounds [Li(py)4]+9a− and [Li(L)4]+(10b–d)− are obtained when (L)Li+1− are reacted with VCl3 and ScCl3. The X-ray structure analysis of the vanadium complex reveals a distorted tetrahedron of the anion [V(1a)4]− with two smaller and four larger CVC angles. The scandium compound [Li(dme)2+10c−] has a different structure: the distorted tetrahedron of the anion [Sc(1c)4]− contains two larger (140.2 and 142.9°) and four smaller CScC angles (93.9–98.7°). This arrangement allows the formation of four bridging BHSc 3c,2e bonds to give an eight-fold coordination. The anion 10c− is formally a 16e complex. 相似文献
7H-Benzocyclohepten-7-one (1) reacts with oxalyl bromide to yield 7-bromobenzocycloheptenylium bromide (4a), a stable carbenium salt. In contrast, the reaction of oxalyl chloride or phosgene with 1 produces a covalent compound, 7,7-dichloro-7H-benzocycloheptent (3b), which ionizes in liquid sulfur dioxide to 7-chloro-benzocycloheptenylium chloride (4b). Nucleophiles are preferably added to C-5 ( C-9) of cation 4a; the resultant products are 7-bromo-5H-benzocycloheptenes (7b-h). The HMO model shows that the positive charge density in 4 is highest at C-5 ( C-9) thus favoring formation of addition products at this position under conditions of kinetic control. In those cases favorable to reversible addition, the competitive nucleophilic substitution at C-7 is the main reaction. The latter reaction occurs between 4a and ?-toluidine or N-methylaniline which produces 7-arylamino-benzocycloheptenylium bromides 13a,b. A further example is the hydrolysis of 4a and 3b to form 1. 相似文献
4-Methoxymethylbenzaldimmonium ions (a) and the corresponding N-methylated ions (b) and N,N-dimethylated ions (c) were easily generated in the ion source by electron impact-induced dissociation from 1-(4-methoxymethylphenyl)ethylamine and its N-methylated derivatives. The spontaneous fragmentations of metastable ions a-c and of specifically deuterated derivatives in the second field-free region of a VG ZAB-2F mass spectrometer were studied by mass-analysed ion kinetic energy Spectrometry. The formation of an amino-p-quinodimethane radical cation by loss of the methoxy group is observed for all ions. In the case of a and b carrying at least one proton at the immonium group, competing fragmentations are the loss of CH2O and CH3OH, respectively, and the formation of ions CH3OCH2+, m/z 45, and C7H7+, m/z 91. Deuterium-labelling experiments indicated the migration of a proton from the protonated imino group of a and b to the aromatic ring followed by the loss of methanol from the methoxymethyl side-chain or protolysis of the bond to either side-chain to form ion-neutral complexes, in close analogy with the reactions of the corresponding protonated benzaldehydes. The intermediate ion-neutral complexes dissociate eventually by internal ion-neutral reactions resulting in the loss of CH2 O and the formation of C7H7+, respectively. 相似文献
The P=icr;S functional group in (η2-PCy2S)Mn(CO)4 (1) undergoes cyclocotrimerization with t-butyl propynoate to give the isomeric compounds 3a und 3b in a 1 : 1 ratio. Oxidation of 3a and 3b with (NH4)2[Ce(NO3)6] gives thiophene 4. Compounds 3a and 3b were characterized by use of MS spectrometry and IR, 31P{1H}, 1H, and 13C{1H} NMR spectroscopy. 相似文献
The crystal structures of the two derivatives of aminomethane-1,1-diphosphonic acid with morpholinyl- (1) and thiomorpholinyl- (2) side chains were determined by single crystal X-ray diffraction and discussed with respect to molecular geometry and solid state organization. The protonation equilibria, solution behavior and complex-formation equilibria in solutions of 1 and 2 with the Zn(II), Mg(II) and Ca(II) ions were studied by means of NMR, pH-potentiometry and ESI-MS methods.As the pK(NH+) protonation constants of 1 and 2 are high (11.65 and 11.91, respectively) two different approaches were used to evaluate the pH-potentiometric data. The first approach disregarded the proton-dissociation from the NH+ group. In the second one, all the pKa values were considered in the M(II):ligand formation equilibria. For 1, the accuracy of the pK(NH+) determination was shown to be sufficient to calculate reliable stability constants of metal complexes with the use of both approaches. For 2, only approach neglecting the pK(NH+) protonation constant was shown to be correct.The studied acids form dinuclear, [M2L3Hx], [M2L2Hx] and mononuclear MLHx and ML2Hx complexes with different degree of ligand protonation. Tendency to undergo some oligomerization with the increase in the metal and ligand concentration was demonstrated for the [CaLH] complex of 1 and 2. As far as 1 and 2 remain protonated, the Zn(II), Mg(II) and Ca(II) ions are coordinated exclusively through oxygen atoms of the phosphonate groups. The metal promoted proton dissociation from the NH+ ring atom takes place in alkaline pH. 相似文献
Thermolysis of As2(4)O3(6) (1) with [(η5-C5Me4R)2Ti(CO)2] (2a: R = Me, 2b: R = Et) affords [(η5- C5Me4R)TiAs3O6] (3a, 3b), molecules with an TiAs3O6 adamantane skeleton. The struture of 3b has been elucidated by X-ray analyis. 相似文献
Stereoregular non-linear chiral main chain polymers 1a–b bonded alternatively with (R,R)-salen and 1,4-diethynyl-2,5-dioctyloxybenzene moieties have been synthesized using palladium catalyzed C–C cross-coupling and Schiff base formation reactions as the key steps. These polymers are soluble in common organic solvents, and act as an effective chemosensor for the detection of Zn2+ with respect to other metal ions with enhanced fluorescence. The CD spectra observed for the polymers 1a–b could be attributed to the helical secondary structure with a low degree of inter-strand interactions. This reduced inter-strand interaction has been ascertained from the titration of pyridine to the Zn(II)-polymer 1b complex, which results in minor changes in the fluorescence emission. 相似文献
A mechanistic study of the reactions between 2-trimethylsilyloxyfuran 1 and (SS)-2-(arylsulfinyl)-1,4-benzoquinones 2a and 2b, giving rise to the diastereoselective formation of [3aS,8bS,SS]-3a,8b-dihydro-7-hydroxy-8-(arylsulfinyl)furo[3,2-b]benzofuran-2(3H)-ones 3a and 3b, is reported. The detection and 1H NMR characterization of several precursors of 3a and 3b accounts for a Michael-type initial reaction which dictates the final diastereoselection of the process. A significant improvement of the stereoselectivity (up to 96% de) in the formation of the tert-butylsulfinyl substituted derivative 3c was achieved by using 2-(tert-butylsulfinyl)-1,4-benzoquinone 2c as the starting quinone. 相似文献
The fragmentation reactions of the MH+ ions of Leu-enkephalin amide and a variety of heptapeptide amides have been studied in detail as a function of collision energy using a QqToF beam type mass spectrometer. The initial fragmentation of the protonated amides involves primarily formation of bn ions, including significant loss of NH3 from the MH+ ions. Further fragmentation of these bn ions occurs following macrocyclization/ring opening leading in many cases to bn ions with permuted sequences and, thus, to formation of non-direct sequence ions. The importance of these non-direct sequence ions increases markedly with increasing collision energy, making peptide sequence determination difficult, if not impossible, at higher collision energies.
The structures of the major adduct ions formed in ammonia chemical ionization of thirteen aliphatic and aromatic ketones have been studied by mass analysed ion kinetic energy spectrometry. The [M+NH3+H]+ ion is shown to have a protonated carbinolamine structure, [M+2NH3+H]+ to be a protonated carbinolamine with hydrogen-bonded ammonia and [2M+NH3+H]+ to be, at least in part, a protonated carbinolamine with hydrogen-bonded ketone. These structures may imply a nucleophilic addition of ammonia at the carbonyl of the ketone-ammonium ion complex. An unusual hydroxy migration is seen in the internal rearrangement of the [2M+NH3+H]+ ion leading to the formation of a protonated imine. 相似文献
The reaction of RHN(CH2)3NHR (1a,b) (a, R=2,6-iPr2C6H3; b, R=2,6-Me2C6H3) with 2 equiv of BuLi followed by 2 equiv of ClSiMe3 yields the silylated diamines R(Me3Si)N(CH2)3N(SiMe3)R (3a,b). The reaction of 3a,b with TiCl4 yields the dichloride complexes [RN(CH2)3NR]TiCl2 (4a,b) and two equiv of ClSiMe3. An X-ray study of 4a (P21/n, a=9.771(1) Å, b=14.189(1) Å, c=21.081(2) Å, β=96.27(1)°, V=2905.2(5) Å3, Z=4, T=25°C, R=0.0701, Rw=0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN2-plane. Compounds 4a,b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH2)3NR]TiMe2 (5a,b). An X-ray study of 5b (P212121, a=8.0955(10) Å, b=15.288(4) Å, c=16.909(3) Å, V=2092.8(7) Å3, Z=4, T=23°C, R=0.0759, Rw=0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium–methyl bond lengths of 2.100(9) Å and 2.077(9) Å. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst·h were obtained in neat 1-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C6F5)3 catalyze the living aspecific polymerization 1-hexene. Polydispersities (Mw/Mn) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph3C}+[B(C6F5)4]−. A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine. 相似文献
p-tert-Calix[6]-1,4-2,5-biscrown-4 was subjected to functionalization by benzyl bromide or ethyl bromoacetate. Two pairs of disubstituted calix[6]biscrown stereoisomers were obtained. Their structures had been deduced from 1H NMR and ESI-MS (electrospray ionization mass spectroscopy). One of the bisethyloxycarbonylmethylated derivatives 3a was further investigated by X-ray crystallographic analysis. Two-phase extraction experiments indicated that bisethyloxycarbonylmethylated derivatives exhibited high Cs+/Na+ selectivity. By ESI-MS and 1H NMR experiments it was confirmed that 3a formed 1:1 complex with Cs+. 相似文献
Abstract The cyclopolymerizations of 1,2:5,6-dianhydro-3,4-di-O-pentyl-D-mannitol (1b) and 1,2:5,6-dianhydro-3,4-di-O-decyl-D-mannitol (1c) were carried out using BF3OEt2 and t-BuOK. All the resulting polymers consisted of cyclic constitutional units, i.e., the extent of cyclization was 100%. The polymer structures for the polymerization with t-BuOK were (1→6)-2,5-anhydro-3,4-di-O-pentyl-D-glucitol (2b) and (1→6)-2,5-anhydro-3,4-di-O-decyl-D-glucitol (2c), whereas those with BF3O-decyl2 comprised 2,5-anhydro-D-glucitols as major units along with other cyclic ones. These polymers were soluble in n-hexane, CHCl3, and THF, but insoluble in water, which differs from the amphiphilic solubility of (1→6)-2,5-anhydro-3,4-di-O-methyl-D-glucitol (2a). The cation-binding properties of 2b and 2c were examined using alkali-metal picrates in order to compare them with those of 2a. The extraction yields for each cation decreased in the order of 2c < 2b < 2a. Every polymer exhibited a similar cation-binding selectivity in the order Cs+ > Rb+ > K+ ? Na+ > Li+. The ratio of K+ and Na+, K+/Na+, was 4.6 for 2a, 5.1 for 2b, and 7.1 for 2c in the increasing order 2a < 2b > 2c. 相似文献