Arene residue

Three configurational isomers are possible for a diazoanhydride with the same (substituted) arene residues on both sides the (Z),(Z), the (Z (E), and the (E),(E), as shown in Scheme 5-15, formulas 5.4, 5.5, and 5.6. Kauffmann et al. think that in their product the residues attached to both azo groups are in the (Z)-configuration. However, their arguments are not clearly convincing. 

De Keukeleire, D., Bako, P., and Van der Eycken, E. (2000) Intramolecular ortho and meta photocycloadditions of 4-phenoxybut-l-enes substituted in the arene residue with carbomethoxy, carbomethoxymethyl, and 2-carbo-methoxyethyl groups. Journal of Photochemistry and Photobiology A Chemistry, 133, 135-146 (c) Wender, P.A. and Dore, T.M. (1995) Intra and inter-molecular cycloadditions of benzene derivatives, in CRC Handbook of Organic Photochemistry and Photobiology (eds W.M. Horspool and P-.S. Song), CRC Press, Boca Raton, pp. 280-290. 

Fig. 20. Molecular models of two conformers of 14-mer duplex d(ATACATGGTACATA) ruthenated at N7 of one of the guanine residues with [Ru(ri6-bip)Cl(en)]+ (10). Conformer (a) shows the intercalation of the arene (b) shows the nonintercalated phenyl ring of the arene stacked on a thymine residue.

Histidine residues are, however, generally regarded as major possible binding sites for ruthenium-arene complexes in proteins. To model this interaction, we also studied the reaction of [RuCl(en)(rj6-bip)]+ (10) with L-histidine at 310 K in aqueous solution (91). The reaction was quite sluggish and did not reach equilibrium until 24 h at 310 K, by which time only about 22% of the complex had reacted. Two isomeric imidazole-bound histidine adducts could be discerned, with more or less equal binding of Ne... 

In calix[4]arenes bearing four anthracene moieties on the lower rim (30),(62) changes in fluorescence intensity are observed on binding of alkali metal ions quenching of fluorescence by Na+ may arise from interaction of four anthracene residues brought in closer proximity to one another enhancement of fluorescence by K+ is difficult to explain. 

Purification of Cjq by fractional crystallization in 1,3-diphenylacetone represents another inexpensive method [230]. After three steps, 99.5% pure was obtained with a total yield of 69%. The purity of Cgg can be increased up to 99.99% by adsorption of the residual C7Q fullerene on charcoal. Preferential precipitation of C7Q over Cgo has been obtained by the addition ofp-trihalohomocalix[3]arenes [231]. 

Phanes are compounds with at least one aromatic nucleus and at least one bridge 28 Such structures can incorporate a great number of arenes — carbophanes contain carbocycles such as benzene or naphthalene, heterophanes heteroaromatic rings including metallocenes — and a wide variety of bridges spanning the ring (s) in different positions from one to several simple alkylidene residues (e.g. hexamethylene or... 

The availability of formation constants for a large number of structurally diverse alkylammonium ions also encourages attempts to identify quantitatively those chemical features of a resident ligand species that are responsible for stability and selectivity within complexes of cucurbituril. In order to secure interpretable results, a subset of data was compiled, restricted to mono-substituted ammonium ions carrying exclusively alkyl or thioether residues [9]. Only included were moieties for which internal complexation with cucurbituril was established (NMR evidence) and for which substrate-specific overcrowding (such as with the arenes) was unlikely. A short list consisting of the first 24 guests in Table 1 was... 

Such units, together with methyl derivatives of ferrocene and cyclopentadienyl (r 6-arene)-iron(II), [FeCp(r 6-arene)]+, have been extensively used as dendrimer peripheral units, but examples of dendrimers containing metallocene residues both as a core and as terminal units and as a core are also reported.5a,b 17... 

Firstly, various side reactions result from impurities left in the diazonium tetrafluoroborate (water, sodium nitrite, washing solvents). As already discussed, residual water or alcohols (often used to wash the solid diazonium tetrafluoroborate after filtration) substitute the diazo group in an ionic process to produce phenols or alkoxyarenes as byproducts. Residual alcohol can also lead to arenes through a radical hydrodediazoniation process, especially when electron-withdrawing groups are present, as in 3-fluoro-2-methoxy-5-(methoxyearbonyl)benzenediazo-nium tetrafluoroborate (ArF/ArH 4 1)227 or in 2-methyl-5-nitrobenzenediazonium tetrafluoroborate.240 Such radical phenomena increase when sodium nitrite is present as impurity... 

Table 4 compiles studies in which 4-[3-(trifluoromethyl)-3//-diazirin-3-yl]arenes are incorporated into peptides, either as congeners, or in the form of the amino acid residue,... 

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