Cyclophanes aromatic compounds

To date the structure and reactivity of numerous complexes derived from aromatic compounds and nitrosonium cation have been studied (5, 56-63). However, relatively few studies are available on the nitrosonium complexes of cyclophanes (5, 57, 59, 61, 62), cf ref. (63). The interaction of [2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by H and 13C NMR spectroscopy using deuterium isotope perturbation technique (64). It was found that the resulting nitrosonium complexes containing one (25) or two NO groups (26) are involved in fast interconversion (on the NMR time scale) (Scheme 17). 

Cyclophanes are known to be efficient receptors for aromatic compounds in protic solvents. Thus, linking a cyclophane unit to a porphyrin, like in 193, provides an excellent way to study the oxidation of aromatic hydrocarbons [117]. The synthesis of 193 took advantage of an earlier protocol for the preparation of strapped porphyrins [118] using the bis-dipyrromethane 194 already linked to the cyclophane as a valuable precursor for an acid catalyzed condensation leading to the porphyrin in 9% yield (Fig. 32). 

The discrepancy between physicochemical and reactivity criteria for aromaticity was known long ago. Yet the data procured by the studies of compounds like 186 or 189 shed a new light on this problem. The observed deviation from planarity did not cause any substantial changes in the spectral parameters of these compounds. Thus they still should be considered aromatic from the point of view of physical chemists. At the same time, this distortion of geometry so dramatically affected their reactivity pattern that, in accordance with this criterion, cyclophanes 186 or 189 should best be referred to as non-aromatic compounds, derivatives of 1,3,5-cyclohexatriene. ... 

Bipyridinium salt-based cyclophane forms stable inclusion complex with dialkoxy aromatic compounds via CT interaction. A few groups ob-... 

Dienes 19 and 20 only react with A-phenylmaleimide (21) when the reactions are activated by high pressure cycloadditions with the more reactive dienophile 1 also occur under thermal conditions, but in lower yield. The reactions are totally a ft-(with respect to the unsubstituted benzene ring of the para-cyclophane unit ) enc/o-diastereoselective. DDQ oxidation of cycloadduct 24 led to the aromatized compound 26 while the aromatization of 23 and 25 failed. Interestingly, the cycloaddition between 1 and 19 led to the aromatized compound 22 this clearly indicates that 1,4-benzoquinone also acts as an oxidant. 

Water-soluble cyclophanes QCP 44 or QCP 66 were impregnated as a carrier into the pores of membrane support. The SLMs showed isomer-selectivity for methylnaphthalenes (MNs), ethylnaphthalenes (ENs), dimethylnaphthalenes (DMNs), and three-ring aromatic compounds. The isomer selectivity of QCP 44 was completely opposite to that of QCP 66 the flux order of QCP 44 was 2-MN > 1-MN, 2-EN > 1-EN, 2,6-DMN > 1,5-DMN, and anthracene > phenanthrene and that of QCP 66 was 1-MN > 2-MN, 1-EN > 2-EN, 1,5-DMN and phenanthrene > anthracene. Cyclophanes exhibited facilitated transport for aromatic but not for... 

The coupling reaction between p-toluenesulfonamide and the appropriate bis(halomethyl)aromatic compound, followed by removal of the tosyl groups, was developed as a simple and general route to the peraza-cyclophanes (Bot-tino et al., 1988 Takemura et al., 1984). In this reaction, carried out under... 

In this chapter, the intermolecular multicomponent aromatic ring construction reactions and intramolecular single-component aromatic ring construction reactions are described. Among them, the [2+2+2] cycloaddition and intramolecular hydroarylation reactions are the most widely employed and reliable method. Various polycyclic and sterically hindered aromatic compounds have been synthesized by this method. In the past 10 years, the asymmetric [2+2+2] cycloaddition and intramolecular hydroarylation reactions have been developed, which enabled the enantioselec-tive synthesis of sterically hindered chiral aromatic compounds, such as axially chiral biaryls, planar chiral cyclophanes, and helically chiral heUcenes. Details of the transition metal-mediated aromatic ring construction reactions are comprehensively covered in the recently published book... 

Cyclophanes, which are bridged aromatic compounds, are probably the most investigated class of host molecules in Supramolecular Chemistry [1]. Among them, the cyclic oligomers derived from the condensation of phenols and formaldehyde, and recently named calixarenes [2], occupy a special place as proved by several books and review articles devoted to the chemistry of these macrocycles [2-6]. The reason for the interest in calixarenes is based on the fact that these compounds can be easily... 

Annulene and dehydro[22]annulene are also diatropic. A dehydroben-zo[22]annulene has been prepared that has eight C=C units, is planar and possesses a weak induced ring current. In the latter compound there are 13 outer protons at 6.25-8.45 8 and 7 inner protons at 0.70-3.45 5. Some aromatic bridged [22]annu-lenes are also known. The [26]annulene has not yet been prepared, but several dehydro[26]annulenes are aromatic.Furthermore, the dianion of 1,3,7,9,13,15, 19,21-octadehydro[24]annulene is another 26-electron system that is aromatic. Ojima and co-workers prepared bridged dehydro derivatives of [26], [30], and [34]annulenes. All of these are diatropic. The same workers prepared a bridged tetradehydro[38]annulene, which showed no ring current. On the other hand, the dianion of the cyclophane 89 also has 38 perimeter electrons, and this species is diatropic. ... 

Multilayered cyclophanes having three aromatic rings fixed in parallel planes above one another exhibit properties intermediate between those of the [2.2]paracyclophanes and the above-mentioned compounds 51 and 52. A cyclic compound of this type, (53), has apparently been isolated by Hubert 77>. The tetracyanoethylene complex of... 

Tertiary and aromatic nitroso compounds react with aryl Grignard or aryl-lithium reagents giving the corresponding hydroxylamines . This reaction is useful for preparation of alkyl- and aiylhydroxylamines (e.g. 109, equation 80 and 110, equation 81) and can be considered as complementary to arylation of hydroxy lamines with activated aryl halides. It has been used for functionalization of cyclophanes with the hydroxy amino group. The main limitation of the reaction is the relatively restricted choice of available aliphatic nitroso components, so most of reactions were done with 2-nitroso-2-methylpropane. There is no literature data about the possibility of removal of the tert-butyl group from these compounds. 

There is no uniformly accepted definition of cyclophanes. Usually one understands under this name a macrocyclic or macrobicyclic compound having built-in aromatic rings. However, IUPAC rules define (cyclo)phanes much more broadly they include linear molecules containing rings that are not necessarily... 

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