Pyrrolothienopyrazines: Synthèse de la pyrrolo[1,2-a]thieno[3,2-e]pyrazine et de la pyrrolo[1,2-a]thieno[2,3-e]pyrazine

The synthesis of pyrrolo[1,2-α]thieno[3,2-e]pyrazine and pyrrolo[1,2-α]-thieno[2,3-e]pyrazine is described. These syntheses could be achieved by intramolecular cyclization of 2- (and 3-) (1-pyrrolyl)-3- (and -2)-thienyl-amines obtained by hydrolysis of carbamates or by cleavage of the corresponding ureas. An original way giving better results was also studied via a Curtius rearrangement by reaction between the azide and aldehyde groupings. The synthesis of 2- (and -3)-2-formyl-1-pyrrolyl)-2- (and -3)-thenoylazide is described.     

Pyrrolothienopyrazines: étude chimique de la pyrrolo[1,2-a]-thiéno[3,2-e]pyrazine

The reactivity of pyrrolol[1,2-a]thienol[3,2-e]pyrazine towards quaternisation, bromination, nitration, sulfonation, Friedel Crafts, Vilsmeier Haack and Reissert's reactions is studied. Assisgnment of structures to the products is based on ir, nmr and mass spectral studies or on unequivocal syntheses.     

Mass spectra of pyrrolo [1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives

The closeness of the electronic structures of the ions formed in the first act of disintegration of the ions is responsible for the monotypic character of the subsequent fragmentation of pyrrolo[1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives. The mass-spectrometric disintegration of the investigated systems has something in common with the fragmentation of thiazolo[3,2-a]benzimidazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1124–1127, August, 1975.     

Synthesis of 5H-imidazo[2,1-c]pyrrolo[1,2-a][1,4]benzodiazepine

We have synthesized 5H-imidazo[2,1-c]pyrrolo[1,2-a][1,4]benzodiazepine 1 in five steps from 1-(2-amino-methylphenyl) pyrrole 4 . Amidino derivatives 11-12 have also been prepared.     

Synthesis of 1H-imidazo[1,2-a]imidazole

The synthesis and structure analysis of the unknown 1H-imidazo[1,2-a]imidazole ( 1 ) is described. The preparation involves alkylation of 2-aminoimidazole with bromoacetaldehyde diethyl acetal and subsequent hydrolysis and cyclization with hydrochloric acid. The structure was characterized by mass spectrometry and by ¹H-, ¹⁵N- and ¹³C-nmr of 1 and by ¹H-nmr of its 1-benzyl derivative 8 . An independent synthesis of 8 was accomplished via cyclization of 2-(N-dichloroethyl-N-benzyl)aminoimidazole ( 11 ).     

Electronic spectra of pyrrolo[2,1-a]isoquinolines and pyrrolo[1,2-f]phenanthridines

The electronic absorption spectra of dioxo-compounds of the pyrroto[2,1-a]isoquinoline and pyrrolo[1,2-f]phenanthridine series and products of their condensation with o phenylenediamine were studied. The influence of substituents was demonstrated; halochromic phenomena in sulfuric acid medium were described; the fluorescence spectra are discussed.Institute of Technical Chemistry, Urals Branch of the Russian Academy of Sciences, Perm' 614600. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 650-653, May, 1995. Original article submitted March 14, 1995.     

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.     

Furo[3,2-e]pyrrolo[1,2-α][1,4]diazepine and derivatives

The 5,10-dihydro-4H-furo[3,2-e]pyrrolo[1,2-α][1,4]diazepin-5-one ( 7 ) and furo[3,2-e]pyrrolo[1,2-α][1,4]diaze-pine ( 10 ) are synthesized from suitable isocyanates 3a,b in acetic acid. The reactivity of 10 (C- and N-alkyla-tion) is investigated.     

One-pot multicomponent cascade reaction of N,S-ketene acetal: solvent-free synthesis of imidazo[1,2-a]thiochromeno[3,2-e]pyridines

Unprecedented imidazo[1,2-a]thiochromeno[3,2-e]pyridines have been synthesized via a three-component cascade reaction under solvent-free conditions. This one-pot transformation involving multiple steps and not requiring the use of transition metal catalysts constructs three new C-C bonds, two C-N bonds, one C-S bond, and three new rings with all reactants efficiently utilized.     

A novel practical synthesis of pyrrolo[1,2-a]thieno[2,3-e][1,4]diazepines

In an investigation of new heterocyclic systems, a novel way to obtain pyrrolo[1,2-a]thieno[2,3-e][1,4]diazepine 8 was effected by ring closure to the appropriate nitroaldehyde compound which was synthesized in five steps from 3-bromomethyl-2-nitrothiophene 1 .     

Phosphorylated imidazo[1,2-a]pyridines

The reaction of phosphorus(III) halides with imidazo[1,2-a]pyridines in the presence of bases leads to the formation of 3-phosphorylated imidazo[1,2-a]pyridines. The reaction proceeds in high yield and requires no catalysts. In the compounds obtained, in contrast to phosphorylated indolizines, the phosphorus–heterocycle bond is stable and not cleaved by dry hydrogen chloride, alcohols, or water. Imidazo[1,2-a]pyridines with the phosphinic and phosphinous groups can be alkylated both at the phosphorus and at the nitrogen atom of the heterocycle, the alkylation direction being dependent on the strength of the alkylation reagent used. © 1995 John Wiley & Sons, Inc.     

First synthesis of 4H-furo[3,2-f]pyrrolo[1,2-a][1,4]diazepines

The synthetic pathway leading to 4-H-furo[3,2-f]pyrrolo[1,2-a][1,4]diazepines is described in five steps starting from 2-hydroxyketones via 2-amino-3-furonitriles.     

Acylation of pyrrolo[1,2-a]pyrazines

The acylation of pyrrolo[1,2-a]pyrazines with acetic anhydride and the acid chlorides of various carboxylic acids has been studied. It has been shown that pyrrole[1,2-a]pyrazines are selectively acylated at the α-position of the pyrrole ring when it is free. Products of the condensation of 1-methylsubstituted pyrrolo[1,2-a]pyrazines have been obtained for the first time in the process of acetylation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 263–272, February, 2008.     

Synthesis and reactivity of furo[2,3-e]pyrrolo[1,2-a][1,4]diazepin-9-one

A convenient method for the synthesis of furo[2,3-e]pyrrolo[1,2-a][1,4]diazepin-9-one is described. It has been C-alkylated with amine (piperidine, morpholine, 4-methylpiperazine) and N-alkylated with alkyl halides (methyl iodide and benzyl chloride).     

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.     

Synthese de pyrrolo[1,2-a]quinoleines

A-Acetoxypyrrolo[1,2a]quinolines 26-30 were synthesized by cyclization of 2-(1-pyrroly)phenylacetic acids 21-25 with acetic anhydride. The structures of the new compounds were determined by ¹H-nmr spectroscopy.     

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.     

Pyrrolo[1,2-a]thiéno[2,3-e]pyrazine. Etude chimique de la dihydro-4,5 oxo-5 pyrrolo[1,2-a]thiéno[2,3-e]pyrazine

The 4,5-dihydropyrrolo[1,2-e]pyrazin-5-one (1) exhibits lactam-lactim tautomerism. N-Electrophilic substitutions could be achieved via the intermediate of the substitutions could be achieved via the intermediate of the sodium salt la. The 5-chloropyrazine 11 obtained by chlorodehydroxylation of pyrazinone 1 allowed nucleophilic substitution. Thionation of the pyrazinone 1 afforded the thioxopyrazine 27 wich gave studied and the tautomerism of the hydrazinopyrazine 14 and its derivatives are discussed in terms of hydrazone and azine structures