Electron aryl derivatives

Mass spectral fragmentation patterns of alkyl and phenyl hydantoins have been investigated by means of labeling techniques (28—30), and similar studies have also been carried out for thiohydantoins (31,32). In all cases, breakdown of the hydantoin ring occurs by a-ftssion at C-4 with concomitant loss of carbon monoxide and an isocyanate molecule. In the case of aryl derivatives, the ease of formation of Ar—NCO is related to the electronic properties of the aryl ring substituents (33). Mass spectrometry has been used for identification of the phenylthiohydantoin derivatives formed from amino acids during peptide sequence determination by the Edman method (34). 

Thiophene [110-02-1] and a number of its derivatives are significant in fine chemical industries as intermediates to many products for pharmaceutical, agrochemical, dyestuffs, and electronic appHcations. This article concentrates on the industrial, commercial, and economic aspects of the production and apphcations of thiophene and thiophene derivatives and details the main synthetic schemes to the parent ring system and simple alkyl and aryl derivatives. Functionalization of the ring and the synthesis of some functional derivatives that result, not from the parent ring system, but by direct ring cyclization reactions are also considered. Many good reviews on the chemistry of thiophene and thiophene derivatives are available (1 7). 

Another multicomponent synthesis giving N-3-substituted compounds 28 consisted of the sequential reaction of metallated phosphonoacetates, in one pot, with a nitrile then an aldehyde and finally an isocyanate. This was an extensive study of the scope and limitations of the different substituents on all the components. The most important feature was that, for good yields, the isocyanate should bear an electron-withdrawing group - tosyl was the most successful. However, an exchange reaction could be carried out by reaction of the tosyl products with aryl isocyanates under microwave irradiation, giving the N-3-aryl derivatives 29 <06CEJ7178>. 

Aryl derivatives of 101 (R=Ar) are planar, and the bond lengths indicate a fully delocalized 10 re-electron aromatic system. By contrast, the (dimethyl-amino) derivative 102 adopts a folded structure. Dithiatetrazocines with exo-cyclic N(Me)Bu groups exhibit both cisltrans and ring inversion isomerism.257... 

The synthetically most valuable intermediate in heterofullerene chemistry so far has been the aza[60]fulleronium ion C59N (28). It can be generated in situ by the thermally induced homolytic cleavage of 2 and subsequent oxidation, for example, with O2 or chloranil [20-24]. The reaction intermediate 28 can subsequently be trapped with various nucleophiles such as electron-rich aromatics, enolizable carbonyl compounds, alkenes and alcohols to form functionalized heterofullerenes 29 (Scheme 12.8). Treatment of 2 with electron-rich aromatics as nucleophilic reagent NuH in the presence of air and excess of p-TsOH leads to arylated aza[60]fullerene derivatives 30 in yields up to 90% (Scheme 12.9). A large variety of arylated derivatives 30 have been synthesized, including those containing cor-annulene, coronene and pyrene addends [20, 22-25]. 

X-Ray crystal structures of aryl derivatives of pyrrolo[2,3- ]pyridines, 29, confirm that steric interactions between the annelated ring and the electron-withdrawing substituent on the 4-position of the pyridine ring cause the pyridine ring to twist out of coplanarity <2006JOC3494>. 

Reissert compounds (l-acyl-l,2-dihydro-2-quinolinecarbonitriles) have been prepared on cross-linked polystyrene and C-alkylated in the presence of strong bases (Entry 8, Table 15.25). Treatment of polystyrene-bound C-alkylated Reissert compounds with KOH leads to the release of isoquinolines into solution (Entry 9, Table 15.25). The reaction of support-bound quinoline- and isoquinoline /Y-oxides with acy-lating agents followed by treatment with electron-rich heteroarenes and enamines has been used to prepare alkylated and arylated derivatives of these heterocycles (Entry 10, Table 15.25 see also Table 15.26). 

Among 6-alkyl and 6-aryl derivatives of salts 228a,b, the location of the maximum (Amax = 652-720 nm) exhibits little dependence on the nature of the heteroatom (2-position) or the substituent at C-6 (68ZOR907 69ZOR961), but rather is determined by the azulene moiety—i.e., by the electronic contribution of heteronium structures like 341b (see Scheme 88). 

Electronic spectra of 1,6,6a SIV-trithiapentalenes are characterized by strong absorption bands near 500 m/a in the visible and near 260 mp. in the ultraviolet. The 500 m/a band is responsible for the orange to red color of trithiapentalenes. The parent compound and its alkyl derivatives may show shoulders of the 260 m/a band near 300 and 230 m/a. Aryl derivatives exhibit a shift of the 500 m/a band toward 470 m/a and the spreading of the 260 m/a band.38,49,92... 

Neutral thiazole and its simple alkyl or aryl derivatives are not reduced polarographically but introduction in the ring of electron-attracting groups may cause the nucleus to undergo reduction <70AHC(12)213>. 

Copper diacetate-catalyzed arylation of heterocyclic amines such as piperidine, tetrahydroisoquinoline 76101 or 1,6-diazacyclodecane 77104 by aryllead triacetates gave only modest to moderately good yields of the iV-aryl derivatives (Equation (76) and (77)). The reactions with aliphatic amines lead to particularly poor yields of the derived anilines101 (Equations (78) and (79)), although the arylation of cyclooctylamine 78 with an electron-rich aryllead triacetate afforded the aniline derivative 79 in a moderately good yield (52%) (Equation (80)).1O5 1O5a... 

Very few data are at present available regarding the basic strength of the isotrithiones. Like the isodithiones (243), they are soluble and stable in strong acids. From the close resemblance of the electronic spectra and of the H-5 shifts in the NMR spectra of the 4-aryl derivatives (253) in carbon disulfide and in trifluoroacetic acid, it is tentatively concluded that the neutral molecule predominates in the equilibrium between 253 and 254.151,156b... 

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