19013-50-4Relevant academic research and scientific papers
Rapid and general protocol towards catalyst-free friedel-crafts C-alkylation of indoles in water assisted by microwave irradiation
De Rosa, Margherita,Soriente, Annunziata
experimental part, p. 1029 - 1032 (2010/04/25)
An efficient and simplified protocol for uncatalyzed FriedelCrafts alkylation of indoles using microwave irradiation in water is described. A series of functionalized indole derivatives has been synthesized in very short times with moderate to good yields. The combination of microwave irradiation and superheated water offers significant advantages over conventional methods, such as higher selectivities, simplicity, shorter reaction times, and no need for a catalyst.
One-pot synthesis of polysubstituted indoles from aliphatic nitro compounds under mild conditions
Simoneau, Christopher A.,Strohl, Alexis M.,Ganem, Bruce
, p. 1809 - 1811 (2008/02/05)
Polysubstituted indoles can be prepared directly from functionalized nitroalkanes under very mildly acidic conditions in a simple, one-pot, two-stage procedure.
Facile synthesis of 2-benzylindoles
Wiedenau, Paul,Blechert, Siegfried
, p. 2033 - 2039 (2007/10/03)
A wide range of 2-Benzylindoles 2 are conveniently and efficiently prepared by heating N-benzylindoles 1 in polyphosphoric acid. Mechanistic studies suggest an intramolecular rearrangement via the corresponding 3- benzyl intermediates.
Zeolites as Catalysts in the Fischer Indole Synthesis. Enhanced Regioselectivity for Unsymmetrical Ketone Substrates
Prochazka, Michal P.,Eklund, Lars,Carlson, Rolf
, p. 610 - 613 (2007/10/02)
The use of zeolites as catalysts in the Fischer indole synthesis has been studied on five unsymmetrical ketone substrates with 14 different zeolites.Both the corresponding phenylhydrazone and the parent ketone in the presence of phenylhydrazine were used as substrates.Zeolites which catalysed the indolization of the phenylhydrazones were also active in the direct conversion of the parent ketone.For substrates which gave mixtures of isomeric indoles under homogeneous, classical indolization conditions in acetic acid, it was found that the distribution of regioisomersof the indoles formed was altered considerably by zeolite catalysis and that the distribution was dependent on the type of zeolite used.A one-pot synthetic procedure for indole synthesis from the parent ketone and phenylhydrazine is described.
On the Role of Lewis Acid Catalysts and Solvents in the Fischer Indole Synthesis
Prochazka, Michal P.,Carlson, Rolf
, p. 651 - 659 (2007/10/02)
The influence of the Lewis acid catalyst and solvent on the Fischer indole reaction has been studied with regard to the distribution of indole isomers in the reaction of phenylhydrazones derived from unsymmetrical ketones.Five ketones, ten solvents and twelve Lewis acids were studied.A multivariate experimental design based on the principal pproperties of the reactants was used to select test systems (substrate, Lewis acid, solvent).A total of 296 of different systems were studied, of which 162 afforded indoles.Analysis of how the properties of these systems are related to the distribution of isomeric indoles was done by PLS modeling.A three-components model was significant according to cross validation and described 87percent of the variance of the isomer distribution.The model showed that the structure of the phenylhydrazone has a dominant influence on isomer distribution; that solvent properties are only wealky involved; and that the properties of the Lewis acid catalyst does not exert any systematic influence on the regioselectivity of the Fischer indole reaction.
Electrophylic Substitution in Indoles. Part 12. Kinetic Studies of the Rearrangement of 3,3-Disubstituted Indolenines to 2,3-Disubstituted Indoles
Jackson, Anthony H.,Lynch, Patrick P.
, p. 1215 - 1220 (2007/10/02)
The rearrangements of 3-alkyl-3-methylindolenine salts to the corresponding 2-alkyl-3-methylindoles have been studied over a range of temperatures by u.v. methods in isopropyl alcohol containing hydrochloric acid.The relativ migratory aptitudes of the various alkyl groups were as follows: Me, 1; Et, 14; Pri, 120; allyl, 400; p-nitrobenzyl, 188; benzyl, 1520.Attempts to prepare the analogous p-methylbenzyl and p-methoxybenzyl-3-methylindolenines by alkylation of the 3-methylindole Grignard reagent gave only the 2-benzylindoles owing to the much higher migratory aptitude of the methylbenzyl and p-methoxybenzyl groups.Spiro hydrochloride rearranged to tetrahydrocarbazole at ca. 7400 times the rate of rearrangement of 3,3-dimethylindolenine hydrochloride to 3,3-dimethylindole.Thermodynamic parameters for the various reactions were determined in view of their relevance to the mechanism of electrophylic substitution in 3-substituted indoles.
Regioselective Indolization of Unsymmetrical Phenylhydrazones by Reaction, at Room Temperature, with PCl3
Baccolini, Graziano,Bartoli, Giuseppe,Marotta, Emanuela,Todesco, Paolo E.
, p. 2695 - 2697 (2007/10/02)
Unsymmetrical ketone phenylhydrazones (1) (R1 ae R2) react with PCl3, at room temperature to give predominantly one, (2), of the two possible 2,3-disubstituted indoles in good to excellent overall yield.When the R1 and R2 groups are very different (R1 = Ph or Me; R2 = alkyl or H) the reaction is highly regioselective leading to exclusive or prevalent formation of the corresponding 3-R1 indoles (2), whereas when R1 and R2 are very similar (R1, R2 = alkyl chains) the regioselectivity is decreased and the indole having the shorter chain in the 3-position predominates, but only slightly.Inspection of the results enables the direction of indolization to be predicted and the positions of the substituents in the 2,3-disubstituted indoles to be assigned with certainty, features not inherent in the classical Fischer indolization.
