Synthesis of new 1,2,3-triazolo[1,2-a]benzotriazoles or 2,3-benzo-1,3a,6,6a-tetraazapentalenes

Some new v-triazolo[1,2-a]benzotriazoles or 2,3-benzo-1,3a,6,6a-tetraazapentalenes were prepared according to previously employed synthetic routes concerning deoxycyclization reactions of appropriate nitrophenyl-1,2,3-triazole derivatives and/or thermal decompositions of appropriate azidophenyl-1,2,3-triazoles. The nitration of 9-phenyl-1,2,3-triazolo[1,2-a]benzotriazoles allowed the isolation of some mononitro- and trinitro-derivatives, whose structures were assigned by chemical and spectroscopic methods.     

Synthesis of 1,2,3-triazolo[1,5-a]pyridine ester derivatives

Lithiation of 1,2,3-triazolo[1,5-a]pyridines 4b and 4c with lithium diisopropylamide (LDA) gave the corresponding lithio derivatives 5b and 5c from which esters 6b and 6c were obtained by treatment with carbon dioxide and then dimethyl sulfate. Lithio derivatives 5a-5c reacted with DMF giving aldehydes 7a-7c. Esters 9a-9c were prepared from aldehydes 7a-7c and carbomethoxymethylenetriphenylphosphorane.     

2,3-Diphenyl-1,2,3-triazolo[1,5-a]pyrimidinium salts

2,3-Diphenyl-1,2,3-triazolo[1,5-a]pyrimidinium salts, the structure of which was confirmed by the PMR spectra, were obtained by condensation of 4-amino-1,5-diphenyl-1,2,3-triazole with -diketones and their analogs in trifluoroacetic acid. The corresponding 4-acylvinylaminotriazoles are formed by the action of alkali on these salts. It was established that the salts with a methyl group in the 7 position do not form polymethine dyes, whereas the 5,7-dimethyl derivative does gives dyes owing to the activity of the methyl group in the 5 position. The ability of the 5,7-dimethyl derivative to undergo cyanine condensations is explained by the betaine cationic structures of the salts obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1422–1424, October, 1978.     

Synthesis of 2,3-Dihydroimidazo[1,2-a]pyridines from 1,3-Diketones

A series of 2-hydroxy-, 2-chloro-, and 2-(2-hydroxyethylamino)-6-aryl-4-polyfluoroalkyl-3-cyanopyridines has been synthesized. The latter react with phosphorus oxychloride to give fluorine containing 2,3-dihydroimidazo[1,2-a]pyridines.     

Synthesis of a new pyrrolo[1,3]diazepine: 4H-pyrrolo[1,2-a]thieno[2,3-e][1,3]diazepine

The 4H-pyrrolo[1,2-a]thieno[2,3-e][1,3]diazepine (20) was synthesized by the one-pot intramolecular cyclization of the appropriate nitroaldehyde 13 . This key intermediate 13 was obtained by two pathways from methyl 3-bromomethylthiophene-2-carboxylate (6).     

Synthesis of substituted pyrrolo[1,2-a][1,3]diazepine. A correction

The structure of a formerly described pyrrol[1,2-a][1,3]diazepine is corrected by synthesis. The correction is discussed by comparing physicochemical data and synthetic procedures for both substances.     

Synthesis of a 1,2,3-triazolo[1,5-a]-1,3,5-triazine. A new heterocyclic system

The synthesis of 3-methyl-7-oxo-5-thioxo-4H,6H-1,2,3-triazolo[1,5-a]-1,3,5- triazine (a new bicyclic system) is described. The key step involves reaction of 4-amino-5-methyl-1,2,3-triazole with carbethoxyisothiocyanate followed by cyclization with alkali.     

Synthesis and transformations of 2,3-dioxo-2,3-dihydroimidazo [1,2-a]-benzimidazole derivatives

9-(H)Alkyl-2,3-dioxo-2,3-dihydroimidazo[1,2-a]benzimidazoles were synthesized by the action of oxalyl chloride on 2-amino-1(H)alkylbenzimidazoles and subsequent cyclization of the resulting 2-amino-1-(H)alkyl-3-chlorooxalylbenzimidazolium chlorides in the presence of triethylamine. The behavior of the synthesized benzimidazoles with respect to the action of alkalis, lithium aluminum hydride, and ethylmagnesium bromide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1391–1395, October, 1976.     

Synthesis of isoxazolo[2,3-a]quinoxalines and pyrrolo[1,2-a]quinoxalines by 1,3-dipolar cycloaddition reaction

The isoxazolo[2,3-a]quinoxalines 11a,b and pyrrolo[1,2-a]quinoxalines 12a,b were selectively synthesized from the 2-substituted 6-chloroquinoxaline 4-oxides 10a,b . The pyrrolo[1,2-a]quinoxalines 12a,b were clarified to be produced by the ring transformation of the isoxazolo[2,3-a]quinoxalines 11a,b . The pyrrolo[1,2-a]quinoxalines 14a,b were obtained from both 2,6-dichloroquinoxaline 4-oxide 9 and compounds 12a,b .     

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.     

Fluorescence studies of some 1,2,3-triazolo[1,5-a]pyridine and imidazo[1,2-a]pyridine esters and their vinylogues

The relative fluorescence intensity of a number of 1,2,3-triazolo[1,5-a]pyridine esters 6 and 7 and imidazo-[1,2-a]pyridine esters 10 and 11 were determined and compared with methyl imidazo[1,2-a]pyridine-5-carboxylate 2 and 4 -methylumbelliferone 3 .     

Preparation of some substituted imidazo[1,2-a]pyridine derivatives

2-Bromopyridine derivatives 2a-2c were prepared. Compounds 2b and 2c and ammonia yielded aminopyridines 3b and 3c which were converted to imidazo[1,2-a]pyridine derivatives 4b and 4c . Compound 4b was nitrated giving the analogue 5b of metronidazole 1 .     

Synthesis of pyrrolo[1,2-a]pyrimidine derivatives

8-Cyanopyrrolo[1,2-a]pyrimidines, the cyano group of which is eliminated when they are heated with phosphoric acid, were obtained by reaction of 2-amino-3-cyanopyrroles with acetylacetone.Compounds Ia, c-g were described earlier in [3], while Ib, h are described in the present work.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1677–1681, December, 1976.     

Thienoquinolizidinones. Synthesis and rearrangement into new piperidino[1,2-a][1,3] or [1,4]diazepinones fused to a thiophene ring

A convenient route to thienoquinolizidinones is described starting from ethyl pipecolinate and suitable halogenomethylthiophenes or 3-chloromethylbenzothiophene. The Schmidt reaction and the Beckmann rearrangement of oximes of these ketones led to piperidino[1,2-a][1,3] or [1,4]diarepines fused to a thiophene ring.