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Indoles diazo-coupling

Diazo coupling occurs very readily between pyrroles and indoles and benzenediazonium salts. Reaction is much more rapid in alkaline solution when the species undergoing reaction... [Pg.55]

Indolizine is much more basic than indole (p Ta = 3.9 vs. —3.5), and the stability of the cation makes it less reactive and resistant to acid-catalyzed polymerization. Protonation occurs at C-3, although 3-methylindolizine protonates also at C-l. Introduction of methyl groups raises the basicity of indolizines. Electrophilic substitutions such as acylation, Vilsmeyer formylation, and diazo-coupling all take place at C-3. Nitration of 2-methylindolizine under mild conditions results in substitution at C-3, but under strongly acidic conditions it takes place at C-l, presumably via attack on the indolizinium cation. However, the nitration of indolizines often can provoke oxidation processes. [Pg.370]

As in the reaction of imidazole, no major isotope effect has been observed 3-deuterioindole reacts at about the same rate as indole. The diazo coupling of five-membered heteroaromatic substrates therefore appears similar to that of homocyclic compounds where, in the absence of steric hindrance, slow attack of the diazonium ion is followed by a fast proton loss.165... [Pg.261]

Indole, like benzothiophene, reacts with electrophiles to give preferentially -substituted products. Bromination241-243 in dioxane or pyridine, nitration by ethyl nitrate,244 chlorination by sulfuryl chloride,245 iodination in aqueous solution,246, 247 Vilsmeier and Reimer-Tiemann formylations,248-261 diazo coupling,252 thio-cyanation,263 and nitrosation254 all give the 3-substituted indoles, practically free from other isomers. [Pg.290]

Diazo coupling occurs readily between pyrroles and indoles and benzenediazonium salts. Reaction is much more rapid in alkaline solution when the species undergoing reaction is the N-deprotonated heterocycle. Depending on the conditions, pyrrole yields either 2-azo or 2,5-bis(azo) derivatives, e.g., 140 or 141, and indole gives a 3-substituted... [Pg.416]

Acylation and metallation studies on monomers, dimers, trimers, and tetramers containing linked thiophen, pyridine, pyrimidine, furan, benzofuran, benzothiophen, and indole moieties have been published/ Deuteriation, halogenation, and diazo-coupling reactions of 2-oxo- and 2-thioxo-l,2-dihy-dropyrimidinium salts have been studied and compared with results for 2,2-dialkyl-1,2-dihydropyrimidinium and 2,3-dihydro-1,4-diazepinium salts in order to demonstrate the effect of an adjacent 0x0- or thioxo-group on the properties of a 1,5-diazopentadienium system/ Vilsmeier formylation of, and tautomerism in, 2-hydroxypyrazolo[5,l-h]quinazolone and l-phenylpyrazolo[5,l-A]-quinazoline-2,9-dione have been studied/ The pyrazolo[3,4-c]pyrazole (71) has been methylated and acetylated, the major products being (72)/ ... [Pg.283]


See other pages where Indoles diazo-coupling is mentioned: [Pg.831]    [Pg.240]    [Pg.299]    [Pg.362]    [Pg.831]    [Pg.240]    [Pg.299]    [Pg.362]    [Pg.831]    [Pg.831]    [Pg.290]    [Pg.296]    [Pg.93]    [Pg.287]    [Pg.175]    [Pg.147]    [Pg.381]    [Pg.607]    [Pg.9]   
See also in sourсe #XX -- [ Pg.47 , Pg.209 ]




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