Thermal reactions of N‐alkyl‐2‐benzylaniline and N‐alkyl‐N′‐phenyl‐o‐phenylenediamine: An unusual route to 2‐phenylindole and 2‐phenylbenzimidazole

A new simple approach to 3‐(2‐acylvinyl)‐2‐(hetero)arylindoles has been developed. The method is based on the acid‐catalysed interaction of 2‐(2‐aminophenyl)furans with(hetero)aromatic aldehydes. The reactions proceed under very mild conditions and lead to indoles containing a reactive α,β‐unsaturated ketone moiety, which is suitable for further transformations, in moderate to good yields.

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Microwave‐assisted Cadogan reaction for the synthesis of 2‐aryl‐2H‐indazoles, 2‐aryl‐1H‐benzimidazoles, 2‐carbonylindoles, carbazole, and phenazine

Creencia

Kosaka

Muramatsu

et al. 2009

Journal of Heterocyclic Chem

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The Cadogan reaction, a widely accepted route for the synthesis of nitrogen containing heterocycles, is modified by using microwave radiation as the source of heat instead of the conventional heating by reflux in a nitrogen atmosphere for several hours. Appropriate starting materials were mixed with triethyl phosphite or triphenylphosphine and irradiated with microwaves for several minutes at a specific power to give the desired products. The indazoles were prepared by irradiating N‐(2‐nitrobenzylidene) anilines with triethyl phosphite at 200 W for 12–14 min to give 85–92% product yields. Irradiation of the mixture of N‐benzylidene‐2‐nitroanilines and triphenylphosphine at 200 W for 3–5 min yielded 93–96% of the benzimidazoles. The carbonylindoles were obtained in 61–68% yields by irradiating 2‐nitrochalcone or alkyl 2‐nitrocinnamates and triphenylphosphine with microwaves at 80–200 W for 8–11 min. The mixture of 2‐nitrobiphenyl and triphenylphosphine yielded 96% of carbazole when irradiated with microwaves at 200 W for 2 min while 75% of phenazine was obtained by irradiating the mixture of 2‐nitrodiphenylamine and triphenylphosphine with microwaves at 200 W for 3.5 min. These results show that microwave‐assisted Cadogan reactions gave better product yields at shorter reaction times. J. Heterocyclic Chem., (2009).

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Thermal reactions of N‐alkyl‐2‐benzylaniline and N‐alkyl‐N′‐phenyl‐o‐phenylenediamine: An unusual route to 2‐phenylindole and 2‐phenylbenzimidazole

Cited by 7 publications

References 37 publications

ChemInform Abstract: Thermal Reactions of N‐Alkyl‐2‐benzylaniline and N‐Alkyl‐N′‐phenyl‐o‐phenylenediamine: An Unusual Route to 2‐Phenylindole and 2‐Phenylbenzimidazole.

ChemInform Abstract: Thermal Reactions of N‐Alkyl‐2‐benzylaniline and N‐Alkyl‐N′‐phenyl‐o‐phenylenediamine: An Unusual Route to 2‐Phenylindole and 2‐Phenylbenzimidazole.

Furan Ring‐Opening/Indole Ring‐Closure: Pictet–Spengler‐Like Reaction of 2‐(o‐Aminophenyl)furans with Aldehydes

Microwave‐assisted Cadogan reaction for the synthesis of 2‐aryl‐2H‐indazoles, 2‐aryl‐1H‐benzimidazoles, 2‐carbonylindoles, carbazole, and phenazine

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