Pyrrolo- and pyrido[1,2-a]indoles via an intramolecular wittig reaction

Several pyrrolo- and pyrido[1,2-a]indoles were prepared via an intramolecular Wittig reaction in good yields. This reaction sequence represents a facile entry into the mitosene ring system.     

Reaction of pyrido[1,2-a]benzimidazole and tetrahydropyrido[1,2-a]benzimidazole with acetylenedicarboxylic ester

Previously unknown polynuclear condensed systems with bridgehead nitrogen atoms have been obtained by treating acetylenedicarboxylic ester with pyrido[1,2-a]-benzimidazole and tetrahydropyrido[1,2-a]benzimidazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–241, February, 1986.     

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.     

One-pot synthesis of pyrrolo[1,2-a]quinoxalines

A transition metal-free process for the regioselective synthesis of pyrrolo[1,2-a]quinoxalines under mild conditions in one-pot is described. The reaction afforded a variety of products in good to excellent yields. Indolo[1,2-a]quinoxalines were also synthesized from indole-2-carboxamides under the same conditions.     

Efficient electrochemical synthesis of pyrido[1,2-a]benzimidazoles

Electrochemical reduction of N-(2-nitroaryl)pyridinium chlorides in alcohol—dilute HCl mixtures gave pyrido[1,2-a]benzimidazoles in high yields in both divided and undivided cells. According to cyclic voltammetry measurements and DFT calculations (B3LYP/6-31+G(d)), the reaction involves intermediate formation of the corresponding hydroxylamine derivative followed by its heterocyclization.     

Synthesis of 3-dimethylphenylsilyl-substituted pyrido[1,2-a]benzimidazoles

Reductive cyclization of 1-(2,4-dinitrophenyl)-3-methyl-4-dimetkylphenyisililpyridinium chloride by the action of phenylkydrazine or hydrogen in the presence of Pd/C gave, for the first time, 7-nitro (amino)-3 dimethylphenylsilylpyrido[l, 2-affienzimidazoles.Russian University of the Friendship of Nations, Moscow, 117923. Translated from Khimiya Geterots ikl icheskikh Soedinenii, No, 3, pp. 338–341, March, 1996. Original article submitted November 27, 1995.     

Synthesis and characterization of pyrido[1,2-a]quinoline palladacycles

Palladacycles of pyrido[1,2-a]quinoline complexes were synthesized via a one pot reaction of quinolines with XyNC (Xy = 2,6-Me ₂C₆H₃) in the presence of Pd(dba)₂ (4:1). These palladacycles were also obtained via reaction of quinolines with Pd(dba)₂ in the presence of PPh ₃ (1:2) in acetone to give the intermediate complexes of dinuclear palladaphosphaquinoline complexes. Dinuclear complexes were converted into palladacycles via reaction with XyNC in CH₂Cl₂. The crystal structure of the dinuclear palladium complex was determined by X-ray diffraction studies. Correspondence: Abdel-Sattar S. Hamad Elgazwy, Department of Chemistry, Faculty of Science, University of Ain Shams, Abbassia 11566, Cairo, Egypt.     

One-pot multicomponent synthesis of polysubstituted indolizines

Concise and efficient four-component tandem approaches to polysubstituted indolizines have been developed under metal-free and mild aerobic conditions in refluxing acetonitrile. The mechanism of the novel reactions was proposed involving the formation of pyridinium ylides and α,β-unsaturated ketones with subsequent 1,3-dipolar cycloaddition and aromatization reaction.     

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.     

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.     

Efficient One-pot Synthesis of Pyrrolo[2,1-a]isoquinoline and Pyrrolo[1,2-a]quinoline Derivatives

A one-pot sequential reaction for efficient synthesis of pyrrolo[2,1-a]isoquinoline and pyrrolo[1,2-a]-quinoline derivatives has been developed. The reaction included firstly the Cu-catalyzed three-component reaction of isoquinoline(quinoline), acetylenedicarboxylate and alkynylbenzene and then Cs₂CO₃-promoted intramolecular cyclization reaction of initially formed 1-alkenyl-2-alkynyl-1,2-dihydroisoquinoline(1,2-dihydroquinoline).     

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.     

One-pot synthesis of imidazo[1,2-b]pyrazole,imidazo[1,2-b]-1,2,4-triazole,imidazo[1,2-a]pyridine,imidazo[1,2-a]pyrimidine,imidazo[1,2-a]benzimidazole,and 1,2,4-triazolo[4,3-a]benzimidazole derivatives

Hydrazonoyl bromides 1a-c react with 5-amino-3-phenyl-1H-pyrazole, 5-amino-1H-1,2,4-triazole, 2-aminopyridine, and 2-aminobenzimidazole to afford the corresponding imidazol[1,2-b]pyrazoles 10, imidazo[1,2-b]-1,2,4-triazoles 11, imidazo[1,2-a]pyridines 16, imidazo[1,2-a]pyrimidines 17, and imidazo[1,2-a]benzimidazoles 20, respectively. Compounds 1a-c reacted also with 2-methylthiobenzimidazole to give 1,2,4-triazolo[4,3-a]benzimidazole derivatives 21. © 1997 John Wiley & Sons, Inc.     

An efficient synthesis of 9H-pyrrolo[1,2-a]indoles

A novel and effective method has been developed for the synthesis of 9H-pyrrolo[1,2-a]indoles by treatment of 3-substituted-4,6-dimethoxyindoles with chalcones in the presence of hydrochloric acid.