Aryl groups, functionalization

The second family of reactions are those in which the aryl group acts as a sub stituent and affects the reactivity of a functional unit to which it is attached... 

A reaction of aryl diazonium salts that does not involve loss of nitrogen takes place when they react with phenols and arylamines Aryl diazonium ions are relatively weak elec trophiles but have sufficient reactivity to attack strongly activated aromatic rings The reaction is known as azo coupling two aryl groups are joined together by an azo (—N=N—) function... 

Fig. 10. Functional groups oxidi2ed by potassium permanganate. Ar is an aryl group.

Although bulky aryl groups, e.g., mesityl, are not effective in stabilizing arylselenium (II) azides, the use of intramolecular coordination in 2-Mc2NCH2C6H4SeN3 has enabled the first structural characterization of this reactive functionality. The Se-Ns (azide) bond length is 2.11 A, while the intramolecular Se N distance is 2.20 A, cf. 2.14 A in the arylselenium bromide 15.5, and 2.13 A and 2.17 A, respectively, in the corresponding chloride and iodide. This... 

The Wolff rearrangement is a versatile reaction R can be alkyl as well as aryl most functional groups do not interfere. The generally mild reaction conditions permit an application to sensitive substrates. 

It is thus clear that P-aryl groups can function as neighboring groups. Much less work has been done on aryl groups located in positions farther away from the leaving group, but there is evidence that these too can lend anchimeric assistance. ... 

It is used to prepare symmetrical RR, where R is straight or branched chained, except that little or no yield is obtained when there is a branching. The reaction is not successful for R = aryl. Many functional groups may be present, though many others inhibit the reaction." Unsymmetrical RR have been made by coupling mixtures of acid salts. 

Table 3 summarizes the scope and limitation of substrates for this hydrogenation. Complex 5 acts as a highly effective catalyst for functionalized olefins with unprotected amines (the order of activity tertiary > secondary primary), ethers, esters, fluorinated aryl groups, and others [27, 30]. However, in contrast to the reduction of a,p-unsaturated esters decomposition of 5 was observed when a,p-unsaturated ketones (e.g., trans-chalcone, trans-4-hexen-3-one, tra s-4-phenyl-3-buten-2-one, 2-cyclohexanone, carvone) were used (Fig. 3) [30],... 

The anodic oxidation reaction of sulphoxides was not much studied, and just a few reports are available so far. The conversion into the corresponding sulphones of some phenyl alkyl and diaryl sulphoxides (oxidation potential for 86 + 2.07 V vs. SCE in acetonitrile/NaC104 electrolyte, Pt anode) has been reported. Similarly, diphenyl suiphoxide was long known to be transformed in a quantitative yield into the sulphone (Pt anode, solvent glacial acetic acid). Additional examples of the oxidation of a suiphoxide function attached to aryl groups are available . 

The term "alkylation covers a variety of techniques in which an active hydrogen atom is replaced in a chemical reaction by an alkyl or, sometimes, an aryl group [436,441,446,448,496]. Functional groups which cem be alkylated are shown below ... 

In our retro-synthetic analysis, we envisioned the pyrrolidinylethanol side chain could be installed via the Ullmann ether formation or the analogous reachons from the aryl-iodide functional group. The key intermediate 9 (cis) in the Medicinal Chemistry route was not stable under strongly acidic or basic conditions since it was easily isomerized to the thermodynamically more stable trans-isomer 9a via... 

Modes of attachment of functional groups to crosslinked polystyrene are discussed ( 1). Attention is drawn to improved stability and activity of polymer-bound reagents and catalysts incorporating dimethylene spacer between polystyrene aryl and functional group heteroatom, and the simplicity and versatility of their synthesis through high-conversion functional group modifications. 

The migratory insertion reactions of the Ta-C functionalities in complexes 113-115 are presented in Scheme 22.9 In the reaction of 113-115 with both CO or Bu NC, the migration, under mild conditions (i.e., room temperature), of both alkyl or aryl groups to form r 2-ketones 116-118 and T 2-imino derivatives, 119-121, has been observed. Unlike the case of [Cp2M] or polyphenoxo derivatives of Ta, migration of the second alkyl or aryl group to the intermediate r 2-acyl or T 2-iminoacyl derivatives is very fast, which prevents the interception of the... 

Reaction of 2-amino-benzyl alcohol and 2-chloroH-phcnylaminopyrimidinc forms the intermediate cation 204, which contains ene and iminium functionalities and undergoes electrocyclic rearrangement to the 2-phenylamino-6//-pynmido[2,l-2 ]quinazoline 205 (Scheme 32). The cation 204 is stabilized by the aryl groups. The 2-NHPh stmcture of the product was confirmed by 111 NMR spectroscopy <2002TL1303>. 

Modified CNTs feature various spectral changes depending on the methods and the location of modifications. These changes include variations in band frequencies, width, and intensities. For example, aryldiazonium salts [139] were used to modify individual sodium dodecyl sulphate (SDS) coated SWNTs with aryl group. The Raman spectrum of functionalized (SDS-free) SWNTs shows a disorder mode much higher than pristine SWNT the radial breathing modes are nearly unobservable. 

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