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1.
The metallation reaction of bromo(alkylthio)benzenes is described. The results show the complementarity of these reactions with the metal-hydrogen exchange reaction. In fact, monometallation of bromo(methylthio)benzenes afforded products substituted in para or meta or ortho to the thioethereal function while bimetallation led to αS,para, αS,meta and αS,ortho disubstituted products. Analogously, the monometallation of 4-bromo-(isopropylthio)benzene afforded para-monosubstituted and ortho,para-disubstituted products.  相似文献   

2.
β,β-Difluoro-α-phenylvinylstannane 3 was prepared in 60% yield from the reaction of β,β-difluoro-α-phenylvinylsulfone 2 with tributyltin hydride in refluxing benzene for 5 h. The cross-coupling reaction of 3 with aryl iodides bearing substituents such as proton, fluoro, chloro, bromo, methoxy, methyl, trifluoromethyl, and nitro on ortho, meta, para positions of the benzene ring in the presence of 10 mol % Pd(PPh3)4/10 mol % CuI afforded the corresponding 2,2-diaryl-1,1-difluoroethenes 4 in 22-82% yields.  相似文献   

3.
In SbF5-HF, reaction of bromine with 2,6-dimethylphenol gives the meta bromo compound 1b which is further halogenated to 3,4-dibromo-2,6-dimethylphenol 1c. In the same conditions ether 2a yields successively 2b and 2d. Meta bromination of compounds 1a,2a,2b implies electrophilic attack on the O-protonated substrate, whereas reaction of the neutral phenol 1b leads to the p-bromoderivative 1c. All products are obtained in excellent yields (> 85%).  相似文献   

4.
Carbon-13 NMR data are reported for thirteen para- and meta-substituted phenyltrimethyltin compounds, RC6H4Sn(CH3)3, where R = para-N(CH3)2, para-OCH3, para-OC2H5, para-CH3, meta-CH3, -H, para-F, meta-OCH3, para-Cl, para-Br, meta-F, meta-Cl and para-Sn(CH3)3. In the para-derivatives, correlation coefficients with Hammet σ-constants of greater than ca. 0.9 are obtained with the tin-carbon couplings to methyl, C1 and C4 carbons, and with the carbon-13 chemical shifts δ(C(1)). In the meta-derivatives, the couplings |J(Sn-CH3)|:, |:J(Sn-C(1))|:, |:J(Sn-C(3))|: and |:J(Sn-C(6))|:, and the shifts δ(C(1)) and δ(C(5)) correlate well with Hammett σ. In the para-derivatives, sensitivity to change in substituent falls off C(4) > C(3, 5) > C(1) > C(2, 6) > CH3 as registered by the δ(C), while in the meta-derivatives δ(C) changes decrease C(3) > C(2), C(4) > C(1) > C(5), C(6) > CH3. The magnitudes of the tin coupling constants decrease C(1) > CH3 > C(3, 5) > C(2, 6) > C(4) in the para-derivatives, while in the meta-series the order is C(1) > CH3 > C(3), C(5) > C(2) > C(6) > C(4). The two sets of one-bond |:J(Sn-CH3)|: and |:J(Sn-C(1)|: values correspond closely to the 0.25/0.33 ratio of coefficients in the LCAO approach, and are interpreted in terms of s-electron redistributions at the tin atom with change in substituent.  相似文献   

5.
Twelve pyridazinones (T1–T12) containing the (2-fluorophenyl) piperazine moiety were designed, synthesized, and evaluated for monoamine oxidase (MAO) -A and -B inhibitory activities. T6 was found to be the most potent MAO-B inhibitor with an IC50 value of 0.013 µM, followed by T3 (IC50 = 0.039 µM). Inhibitory potency for MAO-B was more enhanced by meta bromo substitution (T6) than by para bromo substitution (T7). For para substitution, inhibitory potencies for MAO-B were as follows: -Cl (T3) > -N(CH3)2 (T12) > -OCH3 (T9) > Br (T7) > F (T5) > -CH3 (T11) > -H (T1). T6 and T3 efficiently inhibited MAO-A with IC50 values of 1.57 and 4.19 µM and had the highest selectivity indices (SIs) for MAO-B (120.8 and 107.4, respectively). T3 and T6 were found to be reversible and competitive inhibitors of MAO-B with Ki values of 0.014 and 0.0071, respectively. Moreover, T6 was less toxic to healthy fibroblast cells (L929) than T3. Molecular docking simulations with MAO binding sites returned higher docking scores for T6 and T3 with MAO-B than with MAO-A. These results suggest that T3 and T6 are selective, reversible, and competitive inhibitors of MAO-B and should be considered lead candidates for the treatment of neurodegenerative disorders like Alzheimer’s disease.  相似文献   

6.
Reaction of cyclohexane-1,3-diones with TsCl/Et3N and treatment of the resulting 3-(tosyloxy)cyclohex-2-en-1-ones with aryl- or alkyl thiols and K2CO3 in MeCN gives 3-(arylsulfanyl)cyclohex-2-en-1-ones or 3-(alkylsulfanyl)cyclohex-2-en-1-ones, respectively. These compounds are easily brominated at C-2 by using NBS in MeCN; exposure to DBU in MeCN at room temperature then causes aromatization to afford meta-arylsulfanyl- and meta-(alkylsulfanyl)phenols.  相似文献   

7.
A selective procedure has been developed for the synthesis of 1-chloro(bromo)-substituted borolanes and 2,3-dihydro-1H-boroles by reaction of aluminacarbocycles with boron trihalides BX3 (X = Cl, Br). 3-Substituted 1-chloro(bromo)borolanes and 2,3-dihydro-1H-boroles have been isolated as individual substances, and their structure has been determined.  相似文献   

8.
《Comptes Rendus Chimie》2015,18(3):324-329
The environmental-friendly chlorination reaction of toluene by trichloroisocyanuric acid (TCCA, C3N3O3Cl3) was investigated applying immobilized ionic liquids (ILs) on different supports. Ionic liquids were grafted either on carbon nanofibers (CNF) or encapsulated in zeolites. Their influence on the chlorination activity as well as on the selectivity in different chlorinated products was studied. An unusually high selectivity toward meta-chlorotoluene was achieved, up to 36%. Hence, the selectivity could be tuned to produce either expected ortho-/para-chlorotoluene or meta-chlorotoluene with a proper support choice.  相似文献   

9.
A new strategy based on the use of diethylamine triazenes for stabilization and generation of polymer supported diazonium ions was described. New economical syntheses of four new polymeric supports with 3- and 6-carbon atom spacers and triazene linkers derived from meta- and para-aminophenol were described and compared to the traditional methods. The possible application of the polymer bound triazene masked diazonium salts as supports for immobilization of secondary amines (nortropine and 4-piperidinole and their esterification and oxidation), and as amine scavengers was shown. The new supports with meta-C3-T2 and para-C3-T2 linkers showed higher loadings and typically gave products with good yields and purities.  相似文献   

10.
Proton NMR data at 100 MHz are reported for thirteen para- and meta-substituted phenyltrimethyltin compounds, XC6H4Sn(CH3)3, where X = para-N(CH3)2, para-OCH3, para-OC2H5, para-CH3, meta-CH3, -H, para-F, meta-OCH3, para-Cl, para-Br, meta-F, meta-Cl and para-Sn(CH3)3. Correlation coefficients with Hammett σ-constants of greater than 0.95 are obtained with the methyltin proton chemical shifts and coupling constants to carbon [1J(13C1H)] and tin [2J(SnC1H)]. Solvent effects and other extraneous factors invalidate comparisons of ? values in terms of the relative attenuation of the transmission of substituent effects through homologous carbon, silicon, germanium and tin systems, but coupling constant data reflect a diminution of ca. one tenthfold per bond in the order ?[C(1)Sn] > ? [SnC] > ? [CH]. Satisfactory correlations (r > 0.95) are obtained in this series of closely-related compounds among the conventionally recorded two-bond, 2J(SnC1H) and the constituent, one-bond 1J (Sn13C) and J(13C1H) coupling constants, but the correlation coefficient for the comparison between the two one-bond couplings, 1J(Sn13C) and 1J(13C1H) is lower (r = 0.872). Changes in the couplings at the methyltin carbon bond tin-119 atoms are interpreted in terms of isovalent hybridization; a model based upon effective nuclear charges is tested with respect to both NMR coupling constants and 119Sn Mössbauer Isomer shifts at tin and is invalidated. Proton and carbon-13 NMR, chemical shift and coupling constant data are used to derive a Hammett σ-constant for the para-trimethyltin group of ?0.14, and the significance of this value is discussed.  相似文献   

11.
《Polyhedron》1987,6(6):1399-1405
Visible absorption spectra and the molar-conductance curve for CuBr2 in N,N-dimethylformamide (DMF) as well as the spectra for the Cu(ClO4)2-Et4NBr-DMF and CuBr2-DMF-chlorobenzene systems have been studied. The results indicate the formation of the CuBr3(DMF) complex being the predominating bromo complex of copper(II) in the most concentrated solutions of CuBr2 in DMF. The stability constants of the individual bromo complexes of copper(II) have been determined: log β1 = 3.35, logβ2 = 5.4, and logβ3 = 8.8.  相似文献   

12.
The bromo‐ and iodoaza‐closo‐dodecaboranes HNB11H10Hal (Hal = Br, I), MeNB11H9Br2, and MeNB11H8Br3 are formed from [NB11H11] and MeNB11H11, respectively, by electrophilic halogenation with elementary halogen in the presence of acidic catalysts. Hydrogen in para‐ or in para‐ and meta‐position with respect to the cluster‐N atom is substituted by halogen. With iodine chloride as halogenation agent, all the 11 boron bound H atoms of MeNB11H11 are substituted to give HNB11Cl5I6 with iodine in the para‐ and meta‐ and chlorine in the ortho‐positions, presumably via electrophilic (I) and nucleophilic substitution (Cl). The products are characterized by their NMR spectra, the product HNB11Cl5I6 also by crystal structure analysis.  相似文献   

13.
The reaction of H2PtCl6 with nitrobenzene, o-nitrotoluene, benzoic acid, acetophenone and diphenyl in a CF3COOH/H2O mixture affords the anionic σ-aryl complexes of PtIV. In the case of monosubstituted benzenes, mixtures of meta- and para-platinated isomers were prepared. o-Nitrotoluene also gave rise to two isomers. Electron-witdrawing substituents decrease the rate of introducing the platinum moiety into benzene ring.  相似文献   

14.
A novel isomer of C70(CF3)6 has been isolated by HPLC from a mixture prepared by trifluoromethylation of C70 with CF3COOAg. The X-ray structure revealed an unprecedented arrangement of CF3 groups forming a p3mp ribbon. This result provides additional evidence of the preferable formation of trifluoromethylated fullerene molecules comprising a single continuous ribbon of edge-sharing para- and meta-C6(CF3)2 hexagons.  相似文献   

15.
The transition states of the reaction of electrophilic substitution in a series of ortho-, meta-, and para-carboranes were found by calculations in the B3PW91/6-31G(d,p) and B3LYP/6-31G(d,p) approximations. The key role of catalyst was demonstrated in the reactions of halogenation and alkylation. The reaction selectivity of electrophilic alkylation by CH3Br in the presence of AlCl3 should be lower than that of the chlorination reaction.  相似文献   

16.
Addition of ethylene to the carbanions formed by the metallation of the lithium salts of di- and trimethylphenols by the strongly basic system, n-BuLi-LiK(OCH2CH2NMe2)2 provides a useful synthetic route to a range of alkylphenols. The ease of alkylation of the methyl groups decreases in the order ortho>meta>para while the inclusion of Mg(OCH2CH2OEt)2 in the catalyst restricts alkylation to the methyl groups ortho to the hydroxy group. Dialkylation occurs only at the ortho-methyl groups and only if the adjacent meta-position is unsubstituted. The potential of these products for the synthesis of sterically hindered ligands is outlined.  相似文献   

17.
《中国化学快报》2023,34(7):108042
[1n]metacyclophanes are a class of important building blocks for supramolecular assembly of artificial capsules. Herein we present the preparation and properties of a novel polyfluorinated macrocycle meta-WreathArene, a C2-symmetrical [14]metacyclophane. Adopting a cone conformation in acetone solution, the macrocycle can form dimer capsules through hydrogen bonds induced by chloride anions. Each dimer capsule consists of two meta-WreathArene and two chloride anions, and has been unambiguously characterized both in solution and in solid state.  相似文献   

18.
Two series of new aromatic poly(ester-imide)s were prepared from 1,5-bis(4-aminobenzoyloxy)naphthalene (p-1) and 1,5-bis(3-aminobenzoyloxy)naphthalene (m-1), respectively, with six commercially available aromatic tetracarboxylic dianhydrides via a conventional two-stage synthesis that included ring-opening polyaddition to give poly(amic acid)s followed by chemical imidization to polyimides. The intermediate poly(amic acid)s obtained in the first stage had inherent viscosities of 0.41-0.84 and 0.66-1.37 dl/g, respectively. All the para-series and most of the meta-series poly(ester-imide)s were semicrystalline and showed less solubility. Two of the meta-series poly(ester-imide)s derived from less rigid dianhydrides were amorphous and readily soluble in polar aprotic solvents, and they could be solution-cast into transparent and tough films with good mechanical properties. The meta-series polymers derived from rigid dianhydrides were generally semicrystalline and showed less solubility. Except for one example, the meta-series poly(ester-imide)s displayed discernible Tgs in the range 239-273 °C by DSC. All of these two series poly(ester-imide)s did not show significant decomposition below 450 °C in nitrogen or in air.  相似文献   

19.
《Tetrahedron letters》1986,27(22):2479-2482
Direct diastereoselective chromium complexation of meta-methoxy benzylalcohol derivatives was achieved by the introduction of Me3,Si group, and the benzylic acetoxyl groups of the complexes were substituted with stereochemical retention to lead the key complexes to acorenone and acorenone B.  相似文献   

20.
The regioselective nitration of 25,26,27,28-tetrapropoxythiacalix[4]arene (1,3-alternate) led to the formation of mono- and dinitro derivatives bearing NO2 groups in the meta positions at the same side of the molecule. Their reduction and subsequent condensation with arylisocyanates gave the new types of anion receptors with a so far unknown meta-substitution pattern. In a highly HB-competitive solvent like DMSO, the novel ligands showed good complexation abilities. Moreover, as can be documented by higher complexation constants, achiral receptors 9a, 9b are better preorganized for anion binding than corresponding stereoisomers 10a, 10b. Our results indicate that anion receptors based on meta-substituted thiacalixarenes possess complexation abilities fully comparable with common para-substituted analogues.  相似文献   

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