Electrophylic substitutions

The reaction network may be explained within the concept of the electrophylic substitution in the aromatic ring and the formation of a chemisorbed atomic oxygen species stabilized on strong Lewis acid sites, as it has been proposed in our previous papers [7, 10] ... 

Also, the aromatic polyketones are produced [334] by the reaction of electrophylic substitution (in dispersion) of copolymer of aliphatic vinyl compound (1 -acosen) with N-vinylpirrolydone, at ratio of their links close to equimolar. 

The meaning of stability was recently reviewed [35]. This term refers to three different phenomena. First, aromatic compounds are stable thermodynamically, as they have exceptionally low energy among their isomers. It is well known that benzene is the most stable isomer among the CgH isomers, and so does triphosphabenzene on the C3P3H3 potential energy surface. Second, they are stable kinetically as they do not easily isomerize. Third, they are less reactive than their isomers and their preferred reactions preserve the aromatic moiety of the compounds. Indeed, benzene prefers the electrophylic substitution reactions. 

Further we learned electrophylic substitution reactions of pyrroloindoles. Pyrroloindoles are representatives of n- redimdant aromatic systems. For this reason for them are characteristic reactions with weak and moderate elecrophyles, such as Marmich, Vilsmeier, azo-coupling and other [10-14],... 

Continuing the study of electrophylic substitution in pyrroloindoles ring we decided to learn Vilsmeier reaction in this series. 

In lH,6H-pyrrolo[2,3-e]indole (1), the reactivity of the P-positions in the two different pyrrole rings are not the same. Substitution in the 8-position is difficult owing to shielding by the neighbouring pyrrole ring. It was interesting to elucidate how these factors influence the electrophylic substitution reaction for an equimolar reactant ratio. It was established that three monosubstituted products are formed 3-, 8- and 2-formylpyrroloindoles 34-36 (Scheme 8) [16]. 

Recently Barton et al. (98) reported extremely selective high-yield reactions at —78°C in CFCl3 between fluorine and adamantane and substituted adamantanes. 1-Fluoroadamantane is produced in 84% yield from adamantane, and 3-fluoro-/V-trifluoroacetyl adamantane is produced from /V-trifluoro-acetyladamantane in 83% yield (98). In addition, Barton, Hesse and coworkers reported regioselective reactions of a number of steroids with yields ranging from 25 to 75% (99). Some of the selectivity in the steroids is rather remarkable and is thought to result from electrophyllic reactions that are strongly influenced by polar substituents on the molecules and by solvents (98,99) p. 73. Although the yields are very impressive in these reports, no information is provided on the conversion or the scale. 

The methyl-substituted polyarylesteiketones have been produced in Ref [375] be means of electrophylic polymerization of 4,4 bis-(0-methylphe-noxy)bisphenylketone or l,4-bis(4-(methylphenoxy)benzoyl)benzene with terephthaloyl or isophthaloyl chloride in 1,2-dichloroethane in the presence of dimethylformamides and AICI3. llie polymers have glassing temperature and melting point 150-170 °C and 175-254 °C. 

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