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.     

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.     

A new method for the synthesis of pyrrolo[1,2-a]pyrazines and pyrrolo[1,2-a] quinoxalines

A new method is proposed for the synthesis of pyrrolo[1,2-a]pyrazines and pyrrolo[1,2-a]-quinoxalines. By the alkylation of sodium derivatives of 2-acylpyrroles with -bromo carbonyl compounds or their acetals and subsequent treatment of the reaction products with ammonium acetate in acetic acid, a number of derivatives of pyrrolo[1,2-a]pyrazine, including the first member of the class, pyrrolo[1,2-a]pyrazine itself, have been obtained. Similarly, from 2-benzoylpyrrole and the dimethyl ketal of -bromocyclohexanone was obtained 4-phenyltetrahydropyrrolo[1,2-a]quinoxaline, which readily dehydrogenates in the presence of Raney nickel to form 4-phenylpyrrolo[1,2-a]quinoxaline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp.1048–1050, August, 1970.     

A novel synthesis of pyrrolo[1,2-d][1,4]diazocines from tetrahydropyrrolo[1,2-a]pyrazines using activated alkynes in pyrazine ring expansion

A novel and efficient one-pot synthesis of pyrrolo[1,2-d][1,4]diazocines based on tandem transformation of tetrahydropyrazine ring was elaborated.     

First Total Synthesis of (Z)-11-(2-oxopropylidene)-2,3,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-5(10H)-one

The first total synthesis of naturally occurring (Z)-11-(2-oxopropylidene)-2,3,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-5(10H)-one,a unique cycloanthranilylproline derivative, has been achieved from readily available anthranilic acid in five steps.     

Recyclization of pyrrolo[1,2-a]pyrazinium to 8-aminoindolizine. A new synthesis of the indolizine ring

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, p. 424, March, 1989.     

A new approach to the synthesis of pyrrolo[1,2-a]indole derivatives

Reactions of 2-(3,3-diamino-2-cyanoprop-2-enylidene)indolin-3-ones with amide acetals afforded derivatives of 3-aminomethyleneamino-2-cyano-9-oxo-9H-pyrrolo[1,2-a]indole and 3-amino-2-cyano-9-oxo-9H-pyrrolo[1,2-a]indole. The rate and pathway of the reaction depend on the reagents and solvents. The formation schemes for the compounds obtained were proposed. Their structures were proven by IR and ¹H NMR spectroscopy and mass spectrometry and confirmed by independent syntheses. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2186–2192, December, 2006.     

Photochemical synthesis of 7H-indolo[1,2-a]quinolinium salts - a new ring system

Photodehydrocyclization of 1-phenyl-2-/2-arylethenyl/-3,3-dialkyl-3H-indolium cations leads in very good yield to 7H-indolo[1,2-a]quinolinium cations.     

A one-pot coupling/hydrolysis/condensation process to pyrrolo[1,2-a]quinoxaline

CuI/L-proline-catalyzed coupling of 2-halotrifluoroacetanilides with pyrrole-2-carboxylate esters in DMSO at 80-90 degrees C followed by in situ hydrolysis at 60 degrees C afforded pyrrolo[1,2-a]quinoxalines. Indole-2-carboxylate esters underwent the same process smoothly to provide the corresponding tetracyclic products.     

Synthesis and properties of pyrrolo[1,2-a]pyrazines (review)

The synthesis and properties of pyrrolo[1,2-a]pyrazines are reviewed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1311, October, 1991.     

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.     

Cyclization of 1-benzyl-1,2-dihydro-2-(substituted methylene)quinolines to pyrrolo[1,2-a]quinoline derivatives

1-Alkyl-2-alkylthioquinolinium salts were prepared from 1-alkyl-2(1H)-quinolones via 1-alkyl-2(1H)-thioquinolones in two steps. Under mild conditions, the reaction of 1-alkyl-2-alkylthioquinolinium iodides with active methylene compounds in the presence of sodium hydride afforded 1-alkyl-1,2-dihydro-2-(substituted methylene)quinolines in good yields. The cyclization of 1-benzylquinolines using acetic anhydride produced the corresponding pyrrolo[1,2-a]quinoline derivatives.