Arenes table

Homo- and heterobimetallic complexes of the lanthanides are routinely observed with the large calix[8]arene [191]. However, this extended highly functionalized cavity can also accommodate just one lanthanide ion as shown in [Eu(H6L)(N03XDMF)4] 3DMF (H8L = p-tert-butylcalix[8]arene, Table 13) [192]. Only two adjacent phenolic OH groups were deprotonated according to... 

The structural characterization of a mononuclear Eu-calix[6]arene complex reveals a more unusual complexation mode. In Eu(H4LXOHXDMF)6 (H6L = p-tm-butylcalix[6]arene Table 13) the Eu cation is placed outside the cavity forming only one monodentate bond to the calixarene ligand [193]. Six DMF molecules and most likely a hydroxyl group accomplish 8-coordination. The smaller sized calix[4]arene [194] and ether-extended bis(homooxa)-p-tert-... 

C-H Transformation at Arenes Table 3. Alkene generality of intermolecular coupling of azoles and 3. 

Carbon-centred free radicals may be formed readily either directly from [bis(acyloxy)iodo]arenes, thermally or photochemically, or from added precursors such as alkyl iodides, acids and alcohols, mediated by DIB, BTI or a [bis(acyloxy)iodo]arene. Table 4.7 presents approaches applied for the generation of free radicals in this way. 

The reaction also occurs with a wide variety of substituted arenes (Table V). Electron-donating substituents attached to either the cyclopentadienyl or the arene ring have been shown to enhance the reaction, whereas electron-accepting substituents hinder the reaction 316). The following intramolecular exchange reaction has also been observed 268) ... 

Another factor to be considered is that the hydrogen transfer from Z MH to R is generally faster than R addition onto arene (Table 9.1) [38]. For example, as mentioned earlier (see Section 9.1), the rate of addition of the phenyl radical to benzene is 4.5 x 10 [5]. Therefore, in order to avoid hydrogen transfer competition, the hydride is often added to the reaction mixture slowly (thereby lowering its concentration) by a syringe pump, together with the radical initiator. 

Medium effects on adduct formation are best analysed by considering the solvation properties of the species involved. Thus, using transfer thermodynamic data for p-terr-butylcalix[4]arene (Table I), corresponding values for triethylamine from benzonitrile to nitrobenzene (A(G° = -1.11 kJ mol, Ajl = 1.67 kJ mol and AtS = 9.3 J mol ) combined with the complexation data in these solvents given in Table IV, the thermodynamic parameters for the transfer of the triethylamine-p-tert-butylcalix[4]arene adduct [R3N-calix[4]] between these two solvents are calculated by inserting the appropriate quantities in the following cycle, where P = G, H or S. 

One example has already been encountered in the form of the binding constants in Table 3.2. These data form one of the first examples of compelling evidence for the involvement of attractive arene -arene interactions in determining the outcome of enantioselective catalysis. These attractive interactions have been frequently invoked as explanations for the observed enantioselectivities of... 

Carbon-hydrogen stretching vibrations with frequencies above 3000 cm are also found m arenes such as tert butylbenzene as shown m Figure 13 33 This spectrum also contains two intense bands at 760 and 700 cm which are characteristic of monosub stituted benzene rings Other substitution patterns some of which are listed m Table 13 4 give different combinations of peaks... 

Many aldehydes and ketones are made m the laboratory from alkenes alkynes arenes and alcohols by reactions that you already know about and are summarized m Table 17 1... 

The two mam methods for the preparation of aryl halides halogenation of arenes by electrophilic aromatic substitution and preparation by way of aryl diazomum salts were described earlier and are reviewed m Table 23 2 A number of aryl halides occur natu rally some of which are shown m Figure 23 1... 

NaH should serve as an efficient template ion to yield cone conformers. Conformer distribution for the reaction of p-tert-h Wy calix[4]arene and ethyl bromoacetate is given in Table I. 

Table 1 Conformer Distribution for the Reaction of p-Zerz-Butyl Calix[4]arene and Ethyl Bromoacetate [16]...

Selective extraction experiments were then performed to see transference of some transition elements (Cu ", Ni ", Co ", and Fe " ) from the aqueous phase to the organic phase by the synthesized polymeric calixarenes. Phase-transfer studies in water-chloroform confirmed that polymer 2b and 3b were Fe ion-selective as was its monomer (1). Extraction of Fe " cation with 2b and 3b was observed to be maximum at pH 5.4. Only trace amounts of other metal cations such as Cu, Ni ", and Co " were transferred from the aqueous to the organic phase (Table 3). Furthermore, the extracted quantities of these cations remained unaffected with increasing pH. The effect of pH on the extraction of 3b was lower and 56% extraction was accomplished even at pH 2.2. The extraction experiments were also performed with calix[4]arene (1) the ratio was 8.4% at pH 2.2. The polymeric calix[4]arenes were selective to extract Fe " from an aqueous solution, which contained Cu +, Ni, Co ", and Fe " cations, and it was observed that the... 

What are the reasons for the reactivity differences observed in Table 11.1 Why do some reactants appear to be much more "nucleophilic" than others The answers to these questions aren t straightforward. Part of the problem is that the term micleophilicit > is imprecise. The term is usually taken to be a measure of the affinity of a nucleophile for a carbon atom in the SN2 reaction, but the reactivity of a given nucleophile can change from one reaction to the next. The exact nucleophilicity of a species in a given reaction depends on the substrate, the solvent, and even the reactant concentrations. Detailed... 

Table 2. 1,4-Diazocine Derivatives by the Condensation of 1,2-Dicarboxylic Acid Derivatives with Arene-1.2-diamines...

The nucleophilic substitution of the nitro group in nitro-arene complexes works almost as well as that of Cl" and such substitutions were achieved by Chowdhurry et al. with O, S, and N nucleophiles and with stabilized carbanions [97,98] Eq. (28) and Table 8. 

When the nucleophile is a stabilized carbanion such as the enolate of acetylacetone, 1-benzoylacetophenone, diethylmalonate, or ethyl acetatoacetone, the reaction proceeds similarly. The monosubstituted complex is isolated as long as it contains an acidic hydrogen in the benzylic position. In addition, for the case of diketones CH2(COR)2 (R = Me, Ph, OEt), a deacetylation is observed in an acidic medium [92,93]. These features are the same as described above in the case of the substitution of Cl by stabilized carbanions in monochloroaromatics (the second chlorine being an inert arene substituent [99] Scheme XVII, Eq. (31) and Tables 10 and 11. 

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