Synthesis of quinoxaline derivatives through condensation of 1,2-diaminobenzenes with β-keto sulfoxides

The reaction of o-phenylenediamine with α-methylsulfinylcyclohexanone and α-methylsulfinylcyclopentanone in the presence of acetic acid afforded 1,2,3,4-tetrahydrophenazine and 2,3-dihydro-1H-cyclopenta[b]-quinoxaline, respectively. 3,4-Diaminotoluene and 3,4-diaminochlorobenzene were reacted with α-methyl-sulfinylacetophenone to give a mixture of the corresponding 6- and 7-substituted 2-phenylquinoxaline. Condensation of 3,4-diaminomethoxybenzene with α-methylsulfinylacetophenone gave 7-methoxy-2-phenylacetophenone, whereas, the same reaction between 3,4-diaminonitrobenzene and α-methylsulfinylacetophenone yielded 6-nitro-2-phenylquinoxaline.     

Synthesis of furazano[3,4-b]pyrazine derivatives

Various furazano [3, 4-b] pyrazine derivatives were synthesized by condensation of 3, 4-diaminofurazan with substituted phenylglyoxals, cyclic di- and triketones, and diethyl acetylenedicarboxylate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 613–615, May, 1978.     

Chemistry of furazano[3,4-b]pyrazine. 1. Synthesis and thermodynamic appraisal of 4,8-dihydrodifurazano[3,4-b,e]pyrazine and its derivatives

The thermodynamic stability of the antiaromatic 4,8-dihydrodifurazano[3,4-b,e]pyrazine (I) was studied by a quantum-chemical method. The molecular structure was investigated by x-ray crystallographic analysis, and the aromaticity index of the compound was calculated. It was shown that the oxidation or nitration of compound (I) leads to a stable aromatic radical.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 250–264, February 1997.     

Chemistry of furazano[3,4-b]pyrazine. 4. 5,6-Dichlorofurazano[3,4-b]pyrazine in cyclization reactions

A method was developed for the production of polycyclic compounds containing the furazano[3,4-b]pyrazine fragment by the reaction of difunctional nucleophiles with 5,6-dichlorofurazano[3,4-b]pyrazine. It was shown that the reaction is affected by the hydrogen chloride acceptor (triethylamine). For Communication 3, see [1]. Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11. pp. 1561–1564, November, 1997.     

Reaction of 5-aminopyrazoles with β-dimethylaminopropiophenones. Synthesis of new pyrazolo[3,4-b]pyridines

Several new pyrazolo[3,4-b]pyridines were obtained from the reaction of 5-amino-1-aryl-3-methylpyrazoles 1 with β-dimemylaminopropiophenones 2 in pyridine. The structure elucidation of 4,5-dihydropyrazolo[3,4-b]pyridines 3 is based on nmr measurements and X-ray diffraction. The treatment of compounds 3 with N-bromosuccinimide led to the formation of pyrazolo[3,4-b]pyridines 4 .     

Chemistry of furazano[3,4-b]pyrazine 6. 1,2,3-triazolo[4,5-b]furazano[3,4-b]pyrazines

The reduction of 1,2,3-triazolo[4,5-e]furazano[3,4-b]pyrazine 6-oxide was investigated. By means of data from x-ray crystallographic analysis it was shown that there is a relation between the aromaticity and the structure of the obtained triazoles.For communication 5, see [1].Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1259–1264, September, 1998.     

Reactions of acetylenic β-keto cyanides and β-keto esters with different ammonia derivatives

Different aryl substituted acetylenic β-keto cyanides (IAa-o) and β-keto esters (IBa-o) reacted with each of hydrazine hydrate, phenylhydrazine, hydroxylamine hydrochloride and semicarbazide hydrochloride in boiling alcohol to give the same heterocyclic nucleus for each type of ammonia derivative. In certain cases, intermediate acetylenic hydrazides were isolated at room or zero temperatures and cyclized to give the appropriate pyrazol-5-one compounds when healed above their melting points. It is concluded that Michael addition is favoured at elevated temperatures and Claisen addition is favoured at lower temperatures.     

Chemistry of furazano[3,4-b]pyrazine. 5. 1,2,3-Triazolo[4,5-e]furazano[3,4-b]pyrazine 6-oxides

New representatives of a little-investigated class of compound-1,2,3-triazole 2-oxides — were obtained by a nonphotochemical method. Mononitroamines and dinitroamines are produced during their formation as intermediate products. For Communication 4, see [1]. Latvian Institute of Organic Synthesis Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii. No. 11, pp. 1565–1570. November, 1997.     

Synthesis of pyrido[3,4-b]pyrano[3,4-b]indoles

The synthesis of some pyrido[3,4-b]pyrano[3,4-b]indoles ( 3 ) from 3-hydroxy-4-(3-indolyl)piperidines ( 6 ) is reported.     

Synthesis of stable seleno[3,4-b]quinoxaline derivatives

[reaction: see text]. The unstable seleno[2,3-b]quinoxoline was generated and functionalized in situ to give the stable dialdehyde and diester derivatives. The dicyano compound was made in several steps from biscyanomethyl selenide and was found to be very stable.     

Synthesis of 17β-hydroxy-1′-H-5α-androst-2-eno[3,2-b]pyrrole and 17β-hydroxy-1′-H-5α-androst-3-eno[3,4-b]pyrrole from O-(2-hydroxyethyl)ketoxime precursors

Pyrrolosteroids such as 17β-hydroxy-1′-H-5α-androst-2-eno[3,2-b]pyrrole ( 1 ) and the novel 17β-hydroxy-1′-H-5α-androst-3-eno[3,4-b]pyrrole ( 12 ) can be synthesized from the corresponding O-(2-hydroxyethyl)ketoxime precursors. In the case of 1 , yields compare favourably with previously reported literature methods.     

The chemistry of furazano-[3,4-b]pyrazine. 7. Properties of 5,6-diamino- and 5,6-dihydrazino-furazano[3,4-b]pyrazine

The reactions of 5,6-diamino- and 5,6-dihydrazinofurazano[3,4-b][yrazine that produce polycyclic or highly reactive compounds are reviewed. The furazan ring has a deactivating effect on the amine functions of these compounds. Dedicated to Professor Henk van der Plas on his 70th birthday. For No. 6, see [1]. Latvian Institute of Organic Synthesis, Riga LV-1006 Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 564–573, April, 1999.     

Synthesis of tetrahydroimidazo[1,5-b]-β-carboline derivatives with complex basic substituents

Novel tetrahydroimidazo[1,5-b]-β-carbolines derivatives 6 bearing complex basic chains as substituents on the imidic nitrogen have been prepared in a one-pot reaction. This simple experimental procedure overcomes the direct handle of isocyanates which can be favorably generated “in situ” from carbonyldiimidazole (CDI) and different amines. The stereochemistry of the novel compounds was determined by nmr experiments.     

Synthesis and photovoltaic properties of thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole‐containing conjugated polymers

Novel conjugated polymers composed of benzo[1,2‐b:4,5‐b′]dithiophene and thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole units are synthesized by Stille polycondensation. The resulting polymers display a longer wavelength absorption and well‐defined redox activities. The effective intramolecular charge‐transfer and energy levels of all polymers are elucidated by computational calculations. Bulk‐heterojunction solar cells based on these polymers as p‐type semiconductors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as an n‐type semiconductor are fabricated, and their photovoltaic performances are for the first time evaluated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1067–1075     

Electrochemical properties of pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazine and pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxaline derivatives

The peak potentials (Ep) of 3-substituted pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazine and pyrido[1′,2′:1,2]-imidazo[4,5-b]quinoxaline derivatives are sufficiently correlated with Hammett substituent constant ～_m and with the PM3 calculated LUMO energy levels, and the linear relationship between electron potentials of 9-substituted pyridoimidazoquinoxalines and the LUMO energy levels is also found out.     

Modification and application of 1,2,5-oxadiazolo[3,4-b]pyrazine derivatives: highlights and perspectives

Russian Chemical Bulletin - The review summarized and classified the data on the construction of [1,2,5]oxadiazolo[3,4-b]pyrazine scaffold and its further modifications published over the past 20...     

Synthesis and transformation of N-oxides of some imidazo[4,5-b]pyrazine derivatives

The Böckelheide reaction was accomplished with a number of imidazo[4,5-b]pyrazine N-oxides, and the N-oxidation of the resulting acetoxy(hydroxy)methyl derivatives of imidazo[4,5-b]pyrazine and 6-bromo-1-methylimidazo[4,5-b]pyrazine was studied. The hydrolytic cleavage of 6-bromo-1-methylimidazo[4,5-b]pyrazine and its 4-N-oxide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 690–693, May, 1975.     

Synthesis of trans‐dihydrodiol derivatives of phenanthro[3,4‐b]‐thiophene and phenanthro[4,3‐b]thiophene

The present study describes the synthesis of phenanthro[3,4‐b]thiophene (3) , phenanthro[4,3‐b]thiophene (4) and its potential dihydrodiol metabolites, trans‐6,7‐dihydroxy‐6,7‐dihydrophenanthro[3,4‐b]thiophene (5) and trans‐8,9‐dihydroxy‐8,9‐dihydrophenanthro[3,4‐b]thiophene (6) , trans–6,7‐dihydroxy‐6,7‐dihydro‐phenanthro[4,3‐b]thiophene (7) and trans‐8,9‐dihydroxy‐8,9‐dihydrophenanthro[4,3‐b]thiophene (8) from Suzuki coupled intermediates. The UV spectra of these dihydrodiols are presented. These spectra are useful tools for identifying these dihydrodiols among unknown metabolites of 1 and 2 produced in vitro or in vivo.     

Mass spectra of selected beta-carbolines [β-9H-pyrido(3,4-b)indoles]

The mass spectra of fifteen β-carbolines have been interpreted and proposed fragmentations have been substantiated by means of deuterium-labeling and accurate mass determinations. Most decompositions were predictable. An interesting fragmentation was observed in the spectra of 1-alkyl-1,2,3,4-tetrahydro-β-carbolines, which rearrange to expel an alkylamino (RNH) radical from the molecular ion.