1,2,3,9a-Tetrahydro-9H-imidazo[1,2-a]indoles

When derivatives of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one or 1-carbamoylmethyl-2-methylene-2,3-dihydroindole are reacted with lithium aluminum hydride, derivatives of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indole are formed. Under the same conditions 1-(N-phenylcarbamoylmethyl)-2-methylene-2,3-dihydroindole is not cyclized to an imidazo[1,2-a]indole. WHen treated with proton acids imidazo[1,2-a]indoles are converted to 3H-indolium salts. Opening of the imidazolidine ring is also found when imidazo[1,2-a]indole is acylated with benzoyl chloride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 227–230, February, 1987.     

An efficient synthesis of indolo[3,2-a]carbazoles via the novel acid catalyzed reaction of indoles and diaryl-1,2-diones

A mild and efficient one pot method for the synthesis of indolo[3,2-a]carbazole derivatives by the para-toluenesulfonic acid catalyzed condensation of indole with acyclic 1,2-diones is described. With cyclobutene-1,2-diones the reaction afforded indole substituted carbazole derivatives in good yield.     

Novel Synthesis of 1,2,3,4-Tetrahydropyrazino[1,2-a]indoles

Condensation of 2-(3-methyl-1H-indol-1-yl)ethylamine (7) with benzotriazole and formaldehyde gave 2-(1H-1,2,3-benzotriazol-1-ylmethyl)-10-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indole (8) in 96% yield. Nucleophilic substitutions of the benzotriazolyl group in 8 with NaBH(4), NaCN, triethyl phosphite, allylsilanes, silyl enol ether and Grignard reagents afforded novel 10-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indoles 9a-i in 78-95% yields.     

An efficient synthesis of new polyfunctional hexahydro pyrido[1,2-a]pyrazin-1-ones

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Syntheses of 2-spiroindoles and pyrrolof[1,2-a]indoles

C-alkylated products obtained from methyl 3-hydroxyindole-2-carboxylate afford either spiro compounds, such as an indolic analogue of nitramine, or tricyclic products with a pyrrolo[1,2-a]indole framework. Di-C-alkylated derivatives give access to tetracyclic compounds.     

Cyclisations intramoléculaires: Accés aux 9-oxo-4H,9H-pyrrolo[1,2-a]thieno[2,3-d]pyridine et 4-oxo-4H,9H-pyrrolo[1,2-a]thieno[2,3-d]pyridine. Synthèse des pyrrolo[1,2-a]thieno[3,2-e][1,4]diazepine et pyrrolo[1,2-a]thieno[2,3-e][1,4]diazepine

Synthesis of 1-(2- or 3-thienylmethyl)methyl)pyrrole and some derivatives are described from halogenomethylthiophenes. The intramolecular cyclisation of carboxylic acid 19 and 20 leads to pyrrolothienopyridines 22 and 23. On the other hand azide-aldehydes 29 and 30 in aqueous acid mixture gave the pyrrolo[1,2a]thieno[2,3-e][1,4]diazepine.     

Expedient synthesis of pyrrolo[1,2-a]indoles: preparation of the core of yuremamine

Pyrrolo[1,2- a]indoles are conveniently prepared from tetrahydro-1,2-oxazines, which in turn are generated through the reaction of nitrones with 1,1-cyclopropanediesters. The synthetic route proves to be highly diastereoselective and provides access to the core of the recently discovered pyrrolo[1,2- a]indole natural product yuremamine.     

A facile synthesis of pyrrolo[1,2-a]pyrimidines and pyrrolo[1,2-a]imidazoles

The one-step synthesis of 8-t-butoxycarbonyl-6,7-dimethyl-2-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrimidine from acetyl methyl carbinol, 3-aminopropionic acid, and t-butyl cyanoacetate is reported. Utilizing a similar technology under basic conditions, 7-substituted 5,6-dimethyl-2-oxo-2,3-dihydro-(1H)-pyrrolo[1,2-a]imidazole is synthesized from acetyl methyl carbinol, ethyl glycinate, and the appropriate acetonitrile.     

Fused indoles. 2. Synthesis and reactions of imidazo[1,2-a]- and pyrimido[1,2-a]-indoles

The alkylation of 2-chloroindole-3-carboxaldehyde ( 1 ) and 3-acetyl-2-chloroindole ( 5 ) with 3-chloro-N,N-dimethyl-1-propylamine, 3-chloro-N,N-diethyl-1-propylamine and 2-chloro-N,N-dimethyl-1-ethylamine is described. Following alkylation, demethylation occurs and furnishes imidazo[1,2,-a]- and pyrimido[1,2-a]indoles ( 3a,6,8,10 ). Pyrimido-indole 3a , on treatment with lithium aluminum hydride, furnishes the bis-indole 12 . Analogous reaction with diborane affords the reduced product 14 , while reaction with methyllithium yields the deformylated product 13 . Spectral data of the resulting compounds are also discussed.     

Microwave-assisted combinatorial synthesis of polysubstituent imidazo[1,2-a]quinoline, pyrimido[1,2-a]quinoline and quinolino[1,2-a]quinazoline derivatives

A series of unusual fused heterocyclic compound derivatives, consisting of a pyridine and a imidazole or pyrimidine core, with a bridgehead nitrogen, were successfully synthesized by a microwave-assisted, three-component domino reaction of aldehydes, enaminones, and malononnitrile. In this one-pot reaction, up to five new bonds were formed accompanied by generating the lactam group. This method has the advantages of short synthetic route, operational simplicity, increased safety for small-scale high-speed synthesis, and minimal environment impact.     

A convenient synthesis of 9H-dibenz[c,f]imidazo[1,2-a]azepin-9-ones

A convenient three step synthesis of 9H-dibenz[c,f]imidazo[1,2-a]azepin-9-ones from readily available 2-phenylimidazoline and a methyl benzoate is described.     

The synthesis of novel heteroaryl-fused 7,8,9,10-tetrahydro-6H-azepino[1,2-a]indoles, 4-oxo-2,3-dihydro-1H-[1,4]diazepino[1,7-a]indoles and 1,2,4,5-tetrahydro-[1,4]oxazepino[4,5-a]indoles. Effective inhibitors of HCV NS5B polymerase

Three synthetic approaches have been developed that allow efficient access to novel heteroaryl fused indole ring systems, including: 7,8,9,10-tetrahydro-6H-azepino[1,2-a]indoles, 4-oxo-2,3-dihydro-1H-[1,4]diazepino[1,7-a]indoles and 1,2,4,5-tetrahydro-[1,4]oxazepino[4,5-a]indoles. Each strategy is fully exemplified and the relative merits and limitations of the approaches are discussed. The hepatitis C virus (HCV) non-structural 5B (NS5B) polymerase inhibitory activities of select examples from each molecular class are briefly presented.     

Catalytic asymmetric dipolar cycloadditions of indolyl delocalized metal-allyl species for the enantioselective synthesis of cyclopenta[b]indoles and pyrrolo[1,2-a]indoles

The development of novel synthons and efficient methods to synthesize chiral polycyclic indoles has been a hot topic in organic synthesis and medicinal chemistry owing to their broad applications in medicines, pesticides, and other functional molecules.Here, we disclosed novel indolyl substituted metal-allyl zwitterionic intermediates through the decarboxylation of conveniently available vinyl indoloxazolidones, which could be regarded as two types of dipolar species through the anionic delocalization.The palladium-π-allyl species tended to serve as an all-carbon 1,3-dipole in the asymmetric [3+2] cycloaddition with electrondeficient alkenes, which furnished polysubstituted cyclopenta[b]indoles with high regio-and stereoselectivities. Meanwhile, the iridium-π-allyl species was recognized as an aza-1,3-dipole in asymmetric [3+2] cycloaddition with in situ generated C1 ammonium enolates, affording pyrrolo[1,2-a]indoles with high diastereo-and enantioselectivities. In addition, the dipolar cycloadditions could be easily scaled-up and several synthetic transformations of the cycloadducts were demonstrated for the rapid synthesis of diverse chiral polycyclic indoles.