The first example ot the benzo[b]pyrimido[4,5-f]azocine king system

Base catalyzed cyclization of ethyl 4-[2-(2-amino-4,5-dimethoxyphenyl)ethyl]-2-phenylpyrimidine-5-carboxylate, derived from ethyl 4-methyl-2-phenyl-5-pyrimidinecarboxylate and 3,4-dimethoxy-6-nitrobenz-aldehyde, gave 5,6-dihydro-8,9-dimethoxy-3-phenylbenzo[b]pyrimido[4,5-f]azocine-12(11H)-one, the first reported example of this ring system.     

Transformations of the pyrido[1,2-a]pyrazine ring system into imidazo[1,2-a]pyridines,imidazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes

Transformations of methyl 3-dimethylamino-2-(1-methoxycarbonyl-4-oxo-4H-pyrido[1,2-a]pyrazin-3-yl)acrylate with some cyanomethylenecarbonyl group containing compounds or cyanamide into imidazo-[1,2-a]pyridines, irmdazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes are described.     

Electrophilic substitution of dibenz[b,f]oxepin

Dibenz[b,f]oxepin undergoes nitration and acid-catalyzed deuteration at the 10-position and adds bromine across the 10,11 bond. These reactions contradict predictions made by the SCFMO method. Chemical reactions and NMR spectroscopy suggest that dibenz[b,f]oxepin is only weakly aromatic.     

[1,3,5]Triazino[1,2-a] azepines: A new ring system

The reaction of 2-pyrrolidino-1-aza-1-cycloheptene with aryl isocyanates leads, via 1,4-dipolar cycloaddition, to 1,3-diaryl-10a-pyrrolidinoperhydro[1,3,5]triazino[1,2-a]azepine-2,4-diones. The reaction provides a facile route to the novel [1,3,5]triazino[1,2-a]azepine ring system.     

Formation and amination of dibenz[b,f,-1]azapen-talene dianion: Attempted synthesis of dibenz[b,f,-1]azapentalene

Dibenz[b, f,-1]azapentalene dianion (3) was allowed to react with N,N diethyl - O - mesitylenesulfonylhydroxylamine (4) in order to obtain N,N - diethyl - 5,10 - dihydroindeno[1,2 - b] - indol - 10 - amine (11). The available data indicated that electron transfer processes were involved in the formation of 11. Attempts to obtain dibenz[b, f,-1]azapentalene (1) and 11 by Hofman elimination or by the reaction of 11 with trifluoroacetic acid were unsuccessful.     

Synthesis and properties of novel dibenz[b,f]azocines

5-Acetyl- and 5-trifluoroacetyl-12-hydroxy-11-cyano-5,6-dihydrodibenz[b,f]azocines have been synthesized by intramolecular cyclocondensation of ethyl N-acetyl and N-trifluoroacetyl-N-[1-(cyanomethyl)benzyl]-anthranilates. Spectral data show that the hydroxyl group in 5-acetyl-12-hydroxy-11-cyano-5,6-dihydrodibenz[b,f]azocine takes part in transannular hydrogen bond formation with the acetamide group carbonyl oxygen. A study of the chemical properties of this compound has shown that its alkylation by p, -dibromoacetophenone is accompanied by a Thorpe reaction to form 11-amino-5-acetyl-12-(p-bromo-bemoyl)-5,6-dihydro[b,f]dibenzofuro[2,3-d]azocine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 109–113, January, 1991.     

1,2,4-Triazolo[1,2-a]benzotriazoles: first examples of a novel ring system

-Benzotriazolylamides 6a–d afforded N-(benzotriazol-1-ylmethyl)arylimidoyl chlorides (4a–d), which reacted in situ with potassium tert-butoxide to form 3-aryl-1,2,4-triazolo[1,2-a]benzotriazoles (7a–d) (44–68%), representatives of a novel heterocyclic system. The structure of 7a was confirmed by single crystal X-ray analysis.     

13C NMR studies on dibenz[b,f]azepines

The assignment of the ¹³C nmr resonances of six dibenz[b,f]azepines ( 1-6 ) in dimethylsulfoxide-d₆ was made using chemical shift arguments, coupling to a fluorine substituent, selective proton decoupling, and fully coupled spectra. Exchange of the heterocyclic N-H with deuterium simplified and clarified the coupled spectrum of 1 .     

Substituent-dependent reactivity in the photodimerization of N-substituted dibenz[b,f]azepines

The photoprocesses of a series of N-substituted dibenz[b,f]azepines (iminostilbenes) were studied by absorption and emission spectroscopy, by laser flash photolysis, and by preparative irradiation with NMR analysis. In solutions, 2pi+2pi photodimers of N-cyano and N-acyl dibenzazepines are formed via the triplet state upon acetone- or benzophenone-sensitized energy transfer. T-T absorption spectra were measured and absorption coefficients were determined. The triplet energy transfer is equally efficient for N-alkyl dibenzazepines, which do not dimerize. Excited states of npi* character in the latter cases are discussed to rationalize the different reactivities. In spite of negligible intersystem crossing of 21 dibenzazepine derivatives, photodimers of N-acyl and N-cyano dibenzazepines are formed upon direct excitation in concentrated solutions (0.01-0.1 mol dm(-3)) as well as in the solid state. A selective anti-configuration of the photodimers was found throughout.     

Total assignment of the 1H and 13C NMR spectra of pyrrolizino-[3,4,5-a,b]isoquinoline,benzo[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline

The total ¹H and ¹³C nmr spectral assignments of pyrrolizino[3,4,5-a,b]isoquinoline, benzo-[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline are reported. The concerted use of the COSY, HMQC, HMBC and nOe-difference experiments is used to generate total assignments of the ¹H and ¹³C nmr spectra.     

Thermal ring contraction of dibenz[b,f]azepin-5-yl radicals: new routes to pyrrolo[3,2,1-jk]carbazoles

Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk]carbazole (54% overall yield in two steps from indole). The first substituted pyrrolo[3,2,1-jk]carbazoles have been synthesized by FVP methods and also by reactions of the parent compound with electrophiles, leading to a range of 4-substituted pyrrolocarbazoles.     

Preparation of 8H-Furo[3,4-d]dibenz[b,f]azepine. A Novel Heterocyclic Ring system

The synthesis of 8H-furo[3,4-d]dibenz[b,f]azepine 8 from 5H-dibenz[b,f]azepine 1a is described. The preparation of 8 represents the synthesis of a new heterocyclic system.     

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.     

Two anomalous cyclizations in the dibenz[b,f][1,4]oxazepine series

The cyclization of 3,5′-dichloro-2′-phenoxypropionanilide ( 2 ) to a trimeric cyclohexane 4 and of 4-bromo-5′-chloro-2′-phenoxybutyranilide ( 1 ) to a tetracyclic pyrrolooxazepine 5 is reported.     

Mass spectrometry of the 11H-dibenzo[c,f][1,2]-diazepine system

The mass spectra of 3,8-dichloro-11H-dibenzo[c,f] [1,2]diazepine, the corresponding diazepin-11-01 and diazepin-11-one and their dihydro and N-oxide derivatives have been recorded. The most important fragmentation of the molecular ions of all diazepines studied was an initial loss of m/e 28, with further fragmentation depending on the 11-substituent. No general pathway was observed for the corresponding N-oxides and dihydro compounds.     

Stepwise approach to the 2,3-dihydroimidazo[1,2-a]pyridine and 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine ring systems

The syntheses of 2,3-dihydro-8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 2 ), 8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 9 ) and 5-oxo-8-trifluoromethyl-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-3-carbonitrile ( 3 ) are described. These compounds are constructed in a stepwise approach starting from the properly substituted 2-halopyridines.