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2-Amino-(1-(2-nitrophenylsulfinyl)azulene derivatives were synthesized by the reaction of 2-aminoazulene with 2-nitrobenzenesulfonyl chloride. Crystal structures of these compounds were determined by X-ray diffraction analysis. The sulfur atom derived nosyl group shows unique geometry. Furthermore, a reaction using 4-nitrobenzenesulfonyl chloride is also demonstrated.

Article, TETRAHEDRON LETTERS. 48(26): 4471-4475 (2007)

Polysilsesquioxane having an ethoxysulfonyl group as a side chain was synthesized to prepare a proton-conductive film composed of a main chain of siloxane. At first, sodium 4-(2-methylallyloxy)benzenesulfonate was chlorinated with thionyl chloride. Next, hydrosilylation with trichlorosilane was carried out in the presence of platinum catalyst followed by treatment with ethanol. Finally, the hydrolytic polycondensation was carried out to provide poly(3-(4-ethoxysulfonylphenoxy)-2-methylpropyl)silsesquioxane. This polysilsesquioxane was heated to form a free-standing film that was brittle and brown in color.

2-Chlorocyclohepta[b]pyrroles reacted with o-phenylenediamine to give 2-(2-aminoanilino)cyclohepta[b]pyrroles (2a,b) in good yields. Treatment of 2a and 2b with polyphosphoric acid afforded cyclohepta[1′,2′: 4,5]pyrrolo[1,2-a]benzimidazole (4a) in good yields. Treatment of 2b with acids gave 6-(ethoxycarbonyl) derivatives (4b) of 4a and 12H-5,13-dihydrocyclohepta[1′,2′: 4,5]pyrrolo[2,3-b][1,5]benzodiazepin-12-one (5). Compound 5 was methylated with methyl iodide in the presence of DBU to give 5H-12-methoxycyclohepta[1′,2′: 4,5]pyrrolo[2,3-b][1,5]benzodiazepine, a novel 20π antiaromatic system. Treatment of 2b with sodium ethoxide gave 4b and 2H-1-(cyclohepta[b]pyrrol-2-yl)-1,3-dihydrobenzimidazol-2-one (7a). Compound 5 rearranged to 7a in the refluxing sodium ethoxide-ethanol solution. Reactions of 2a and 2b with triethyl orthoformate gave corresponding 1-(cyclohepta[b]pyrrol-2-yl)benzimidazoles. Reactions of 2a and 2b with acetic anhydride are also mentioned.

3-Iodo-1-azaazulenes were easily ethynylated by Sonogashira-Hagihara reaction to give 3-ethynyl-1-azaazulenes. Cyclization of 2-amino-3- ethynyl-1-azaazulene was achieved by heating in the presence of copper(II) acetate or copper(II) trifluoromethanesulfonate, and 1,9-diaza-1H-cyclopent[a]azulene derivatives were obtained. Reaction of 2-chloro-1-azaazulene with lithium phenylacetylide gave 3-chloro-1-(2-chloro-1-azaazulen-8-yl)-2-phenyl-2a-aza-2H-cyclopent[cd]azulene together with 2-chloro-8-phenylethynyl-1-azaazulene.

The addition reactions of 3-(2-chloro-1-azaazulenyl)methylene with cis- and trans-stilbenes proceeded in a stereospecific manner to afford the corresponding cyclopropane derivatives. The substitution effects on the relative rate ratio of the addition reactions of the carbene with styrenes having various substituents on the p-positions were measured to investigate the electronic nature of carbene.

2-Hydrazinocyclohepta[b]pyrrole reacted with dimethyl acetylenedicarboxylate (DMAD) to give the hydrazones (2a), the pyrimidinone-fused cyclohepta[b]pyrrole (3), 1,2,4-triazinone-fused cyclohepta[b]pyrroles, and the 1,2-dihydro-3H-pyrazol-3-one derivative. Thermolysis of 2a gave 3 and tetramethyl pyrrole-2,3,4,5-tetracarboxylate. The reaction of ethyl cyclohepta[b]pyrrole-3-carboxylate with DMAD at room temperature gave the hydrazone and the spiropyrazoline derivative.

Cycloadditions of the title compounds with dimethyl acetylenedicarboxylate gave 1:2-cycloadducts. The structural assignments of the products were deduced by spectral inspections; the structure for one compound was established by X-ray crystallography.

Reactiond of 2-(N, N-dimethylamino)- and 2-(N, N-diethylamino)tropones with palladium (II) acetate in benzene in the presence of sodium acetate afforded the corresponding 7-acetoxylated 2-aminotropones. A similar acetoxylation reaction proceeded with azulene to give 1-acetoxy- and 1, 3-diacetoxyazulenes. On the other hand, phenylation at the 7-position occurred in the reaciton using 2-(N-methyl)anilinotoropone. The acetoxylations are considered to proceed through radical cation complexes formed through oxidation of amino groups by palladium.

3,4-Dibenzoyl-1-phenyl-2a,5-diazabenz[cd]azulene (2b) was synthesized by cycloaddition of 8-amino3-phenyl-1-azaazulene with dibenzoylacetylene. Heteroannulation to 2b has been achieved by reactions with hydrazine and phosphorus pentasulfide.

Reaction of 2-chlorocyclohepta[b]pyrrole-3-carbaldehyde with o-phenylenediamine gave 1H-2-(2-chlorocyclohepta[b]pyrrol-3-yl) benzimidazole (3a) and 5H-12,13-dihydrocyclohepta[1′,2′:4,5]pyrrolo[2,3-b][1,5]benzodiazepine (4a). Some reactions of 3a and 4a were also described.

Aldol condensation of 2,3-diformyl-1-azaazulene with acetone, methoxyacetone, and benzylacetone in aq. NaOH solution gave corresponding 11-azacyclohept[α]azulen-3(3H)-one (2a), 2-methoxy-derivative (2b) and 2-benzyl-derivative (2d) in good yields. Hydrolysis of 2b using hot HBr gave 2-hydroxy-11-azacyclohept[a]azulen-3(3H)-one (2f). Acetylation of 2f gave 2-acetoxy-11-azacyclohept[α]azulen-3(3H)-one (2g). Reaction of the compounds (2a, 2b, 2f) with diethyl malonate in Ac 2 O under heating gave 1,9(11bH)-11b-azaazuleno[1,2,3-cd]azulenedione derivatives (4a, 4b, 4f). Compounds (2b, 2f) showed weak cytotoxic activity against HeLa S3 cells.

2-(2-Pyridyl)-l-azaazulenes were derived from 2-bromo- or 2-iodo-1-azaazulenes and 3-(2-pyridyl)-l-azaazulenes were derived from 3-iodo-1-azaazulenes by Suzuki coupling. Reaction of 3-iodo-1-azaazulenes with B(NPDEA) gave corresponding 3-(2-pyridyl)-1-azaazulenes together with 3-borylated-2-chloor-1-azaazulene (9a) or 3,3'-bi(2-methoxy-l-azaazulene) (lOb). Reactions of 8-(2-pyridyl)-l-azaazulene with 2-pyridyllithium gave 4,8-di(2-pyridyl)- and 6,8-di(2-pyridyl)-l-azaazulenes. Reactions of 4,8-di(2-pyridyl)-l-azaazulene with 2-pyridyllithium gave 4,6,8-tri(2-pyridyl)-1-azaazulene. The reactivity of the seven-menbered ring is C8 > C6 > C4. Reaction of 3-(2-pyridyl)-l-azaazulenes with 2-pyridyllithium gave 3,4-di(2-pyridyl)- and 3,8-di(2-pyridyl)-1-azaazulenes.

Heteroarylamination and heteroarylsulfidation of 2-chloro-1-azaazulenes (1) were investigated. Palladium catalyzed coupling of 2-amino-1-azaazulenes (2) with 1 underwent to give bis(1-azaazulen-2-yl)amine derivatives in good yields, but the reaction of 2-mercapto-1-azaazulenes (4) with 1 did not give good results in the same conditions. The reaction of 4 with 1 under basic conditions gave bis(1-azaazulen-2-yl) sulfide derivatives in good yields. Heteroarylamino-substitution was proceeded on the reaction of 4-amino-3-mercapto-4H-1,2,4-triazoles (6) with 1 in BuOH under reflux, whereas heteroarylsulfido-substitution was proceeded on the reaction of 6 with 1 in the presence of NaH in dioxane. The chemistry of azaazulenes is of interest for their physiological properties as well as physical and chemical properties. Aryl amines have a potential functionality in pharmaceutical drug candidates, therefore Pd-catalyzed amination of aryl halides has attracted attention. Recently, we reported that heteroarylaminatition of ethyl 2-chloro-1-azaazulene-3-carboxylate proceeded well by Pd-catalyzed amination. In the extension of the chemistry, we examined the reaction of 2-chloro-1-azaazulenes with 2-amino-1-azaazulenes, mercapto-1-azaazulenes, and 4-amino-3-mercapto-4H-1,2,4-triazoles. Treatment of 2-chloro-1-azaazulene (1a) with 2-amino-1-azaazulene (2a) in the presence of Pd2(dba)3, Xantphos, and Cs2CO3 in dioxane under reflux for 4 h gave bis(1-azaazulen-2-yl)amine (3aa) in 39% yield. The H NMR spectrum of 3aa was symmetrical and the C NMR spectrum showed 9 signals; this showed that heteroarylamination occurred at amino group at C-2, and not at N-1 of 1-azaazulene nuclei. Similar treatment of 1b, 1c, and 1d with 2a and 2b gave 3ba (70%), 3ca (63%), and 3db (43%), respectively. Although the yields were slightly low as the case, the usefulness of Pd-catalyzed heteroarylamination was certified for the synthesis of bis(1-azaazulen-2-yl)amine derivatives.

Facile syntheses of 2-, 3,- and 8-(2-benzimidazolyl)-1-azaazulenes (2a-c, 5, 7, 9) and 2-, 3-, and 8-(2-benzothiazolyl)-1-azaazulenes (13b-c, 16, 17, 18) were achieved by the condensation of corresponding 1-azaaazulene- carbaldehydes with o-phenylenediamine and 2-aminothiophenol in alcoholic solvents at rt or under reflux under airobic conditions. Reaction of 1-azaazulenecarbaldehyds with 2-aminophenol gave Schiff's bases (10a-c, 11, 12). Reaction of 2-chloro-1-azaazulene-3-carbaldehyde (1a) with 2-amino- thiophenol in refluxing 1-BuOH gave benzothiazapine-fused 1-azaazulene (20). Reaction of 4-amino-3-mercapto-4H-1,2,4-triazoles (21a-d) with in refluxing 1-BuOH gave triazolothiadizapine-fused 1-azaazulene (22a-d). The structure of trifluolomethyl derivative (22c) was determined by X-ray structure analysis. 3-(2-Benz- imidazolyl)-2-chloro-1-azaazulene (2a) showed anticancer activity against HeLa S3 cells (IC50: 5.3 µM).

Trimethylsilylethynyl)- and 3-(phenylethynyl)-2-(triphenyl- phosphoimino)-1-azaazulenes were synthesized by the Appel reaction of the corresponding 2-amino-3-ethynyl-1-azaazulenes. Reaction of 3-(phenyl- ethynyl)-2-(triphenylphosphoimino)-1-azaazulene (8b) with Cu(OTf)2 gave 3-(2-oxophenethyl)-2-(triphenylphosphoimino)-1-azaazulene (11), 3-(1,2-dioxo- phenethyl)-2-(triphenylphosphoimino)-1-azaazulene (12), and 2-amino-3-(1,2- dioxophenethyl)-1-azaazulene (13). The structure of 13 was decided by X-ray structure analysis, and the structure of 12 was discussed by molecular orbital calculation. Reaction of 8b with aryl isocyanate in the presence of benzoyl peroxide gave 1,10-diazabenz(a)azulene derivative.

3-Ethynyl-1-azaazulene derivatives were obtained by Sonogashira-Hagihara reaction of 3-iodo-2-chloro-1-azaazulenes, and 2-(phenylethynyl)-1-azaazulenes were obtained by the reaction of 2-bromo-l-azaazulenes. Glaser reaction of 2-chloro-3-ethynyl-1-azaazulenes gave 1,4-bis(2-chloro-1-azaazulen-3-yl)-13-butadiyne. Treatment of 2-chloro-3-ethynyl-1-azaazulene derivatives with sodium hydrosulfide gave corresponding 1-thia-9-azacyclopent[a]azulene derivatives in good yield.

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ‐‐ Styryl-1-azaazulenes were synthesized by two ways: a) Suzuki coupling of 2-bromo-1-azaazulenes with trans-2-phenylvinylboronic acid b) Condensation of 2-methyl-1-azaazulene, being synthesized by

Reaction of 2-triphenylphosphoimino-1-azaazulenes (4a-c), prepared from 2-amino-1-azaazulenes, with some aryl isocyanates gave 2-arylimino-3-aryl-2,3,4,4a-tetrahydro-1,3,4a-triazabenz[a]azulen-4-one (6) as major products.Reaction of aryl isothiocyanates gave 2-arylimino-3-aryl-2,3,4,4a-tetrahydro-l,3,4a-triazabenz[a]azulene-4-thiones (10).

The reaction of 8-(triphenylphosphoimino)quinoline with aryl aldehydes gave 2-aryl-4H-imidazo[4,5,1-ij]quinolines. In the reaction, tandem aza-Wittig reaction and cyclization attended with hydride shift occurred. The reaction of 8-(triphenylphosphoimino)quinoline with aryl isocyanates gave 1,3-diaryl-1,2,3,9a-tetrahydro[1,3,5]triazolo[2',3':2,1;3',4'-a]imidazo[4,5,1-ij]quinolin-2-ones (11) and 2-(arylamino)imidazo[4,5,1-ij]quinolin-4(4H)-ones (12). The structures of 11a (Ar = Ph) and 12a (Ar = Ph) were confirmed by X-Ray structure analyses.

2-Chloro-, 2-methoxy-, and 2-amino-l-azaazulenium 1-methylides and 1,3-diazaazulenium 1-methylide were generated by the treatment of the corresponding 1-trimethylsilylmethyl-1-azaazulenium triflates and 1-trimethylsilylmethyl-1,3-diazaazulenium triflate with CsF; the triflates were prepared from the corresponding 1-azaazulenes and 1,3-diazaazulene with trimethylsilylmethyl triflate. The 1,3-dipolar cycloadditions of the 2-chloro-1-azazaazulenium 1-methylide, prepared in situ, with acetylenic esters gave 2a-azabenz[cd]azulene derivatives and 3a-azacyclopenta[a]naphthalene derivatives as major products, whereas 2-piperizino-1-azaazulenium 1-methylide underwent extended dipolar cycloaddition with acetylenic esters and afforded 9b-azacyclopent|a]azulene derivatives as major products.

Reaction of 3-phenyl-8-triphenylphosphoimino-1-azaazulene (1) with some aryl isocyanates gave 2-arylimino-4-phenyl-2,2a-dihydro-1,2a-diazacyclopent[cd]azulenes (2) and 8-arylimino-1,8-dihydro-1-azaazulenes (3). Reaction of 1 with p-toluenesulfonyl isocyanate gave 2-imino-3-(p-methylphenyl)-4-phenyl-2,2a-dihydro-1,2a-diazacyclopent[cd]azulene as cyclization-rearrangement product. Reaction of phenyl isothiocyanate gave 2. Tautomerization of between 8-imino-1,8-dihydro-1-azaazulenes (3) and 8-amino-1-azaazulenes was discussed on the basis of X-Ray structure analysis and molecular orbital calculation.

Reaction of 3-phenyl-8-triphenylphosphoimino-1-azaazulene (1) with arylaldehyde gave 2-aryl-4-phenyl-3H-1,2a-diazacyclopent[cd]azulenes. Reaction of 1 with trans-cinnamaldehyde gave 3-benzyl-1-pheny-2a,5-diazabenz[cd]azulene as cyclization product. Cycloaddition reaction of 1 with dimethyl acetylenedicarboxylate gave tetramethyl 4-phenyl-9,9b-diazaindeno[4,3a,3,2-bcd]azulene-1,2,3,9a-tetracarboxylate and hexamethyl 6-phenyl-3aH-10c-azaacephenanthryene-1,2,3,3a,4,5-hexacarboxylate.

Reaction of 2-chloro-1-azaazulenes with 2-pyridyllithium followed by dehydrogenation by chloranil gave 8-(2-pyridyl) -1-azaazulene (2). Formation of metal complexes (M = Cu, Fe, Pd) of 2 was achieved. The reaction of 2 with Cu(1) gave 1:1-complex (3) and 2:1-complex (4). Complex (3) was deduced to have a polymeric chain structure with the copper center is +1. The ESR spectrum study of 4 showed that the copper center is +2. The structure of 4 was decided by X-Ray structural analysis and it is shown that the complex takes a trigonal bi-pyramidal structure.

2-Substituted 1-azaazulene N-ylides were generated by the treatment of appropriate 1-trimethylsilylmethyl-1-azaazulenium triflates with CsF; the triflate salts were prepared from 1-azaazulenes and trimethylsilylmethyl triflate. The 1,3-Bipolar cycloadditions of 2-chloro-1-azaazulene N-ylide, prepared in situ, with acetylenic esters gave 2a-azabenz[cd]azulene derivatives and 3a-azacyclopent[a]naphthalene derivatives. These structures were determined by X-Ray crystal structure analysis. A similar reaction of 2-piperidino-1-azaazulene N-ylide gave 3a-azacyclopent[a]azulene derivative as major product.

Chloroketene reacted with 8-amino-3-phenyl-1-azaazulene (1) to give 2,2a-dihydro-2a-azacyclopent[cd]azulen-2-one derivative (2a), as a cycloadduct, along with ethyl (3-phenyl-1-azaazulen-8-yl)aminocarboxylate (3a) and 8-chloroacetylamino-3-phenyl-1-azamulene (4a). Compound (2a) was formed by the reaction of 4a with chloroketene. Formation mechanism of 2a, 3a and 4 was discussed. Phenylketene and diphenylketene reacted with 1 to give 8-phenylacetylamino- (4b) and 8-diphenylacetylamino-3-phenyl-1-waazulene (6) as major products,respectively. Further treatment of 6 with diphenylketene gave 2-diphenylmethylene-4-phenyl-2,2a-dihydro-1,2a-diazacyclopent[cd]azulene (7).

3-Phenyl-7,8-dehydro-1-azaazulenes were generated by the treatment of 8-bromo-3-phenyl-1-azaazulenes with potassium t-butoxide in DMSO or in THF in the presence of 16-crown-8-ether, and trapped with diphenylisobenzofuran as 3,7,12-triphenyl-1-aza-7,12-epoxynaphth[2,3-e]azulenes. The structure of the adduct, 2-bromo-3,7, 12-triphenyl-1-aza-7,12-epoxynaphth[2,3-e]azulene, was deduced by X-Ray structure analysis. Similar treatment of 8-bromo-3-phenyl-1-azaazulene with potassium t-butoxide in the presence of furan gave 3-phenyl-1-aza-7,12-epoxynaphth[2,3-e]azulene and 7-phenyl-3H-3a,3c-dihydro-1-aza-3-oxacyclopenta[3,4]cyclobuta[1,2-e]azulene as cycloadducts.

Ethyl (2-alkylimino-1,2-dihydro-1-azaazulen-1-yl)acetates (3) were synthesized from 2-alkylamino-1-ethoxycarbonylmethyl-1-azaazulenium salts, which were produced from 2-alkylamino-1-azaazulenes with ethyl bromoacetate. Reaction of 3 with acid anhydrides gave the mesoionic anhydro-3-acyl-1-alkyl-2-hydroxy-1,3a-diazacyclopent[a]azulenium hydroxide. Polar cycloaddition of 3 with methyl propiolate gave methyl 2-alkyl-1-oxo-1,2-dihydro-2,9b-diazaindeno[3,3a,4,5-bcd]azulene-8-carboxylate and 3-ethyl 5-methyl 2-alkylamino-2a-azabenz[cd]azulene-3,5-dicarboxylate.

Reaction of 2-amino-1-azaazulene with diphenylcyclopropenone gave 1,2-diphenyl-1,2,3,1Ob-tetrahydro-4, 10b-diazabenz [a] azulen-3-one, which rearranged to N-(1-azaazulen-2-yl)-α-cis-stylbenecarboxamide and N-(1-azaazulen-2-yl)- α -trans-stylbenecarboxamide by heating. Some structures of these products were determined by the X-ray structure analyses. The reaction mechanism is discussed

8-[(E)-Styryl]-1-azaazulenes stereospecifically react with dimethyl acetylenedicarboxylate to form trans-7H-6a-azacyclobuta[j]cyclopent[cd]azulene (3), which undergoes thermal rearrangement into 3-[(E)-styryl]3H-2a-azacyclopent[cd]azulene and 3a,4-dihydro-3H-2a-azadicyclopent[cd, ij]azulene (7), or isomerization into 3H-2a-azacyclopenta[ef]heptalene by silica gel. Compound 7 is oxidized during the course of reaction to yield 11-oxo-2aH-7,10b-methano-2a-azacyclopenta[ab]cycloundecene, compound 3 forming 5a,6-dihydro-3H-2a-azadicyclopenta[ef, kl]heptalene upon reaction with acetylene. The formation of 3 could be accounted for in terms of a symmetry-allowed thermal [π2s+π2a+π6a] cycloaddition.

The reaction of 2-aminocyclohepta[b]pyrroles with ethyl acetoacetate in phoshoryl chloride–polyphosphoric acid gives 2-methyl-4H-cyclohepta[4,5]pyrrolo[1,2-a]pyrimidin-4-ones. A ring closure of diethyl N-(cyclohepta[b]pyrrol-2-yl)aminomethylenemalonates gives 4-oxo-4H-cyclohepta[4,5]pyrrolo[1,2-a]pyrimidine-3-carboxylates (2) in phosphoryl chloride–polyphosphoric acid or in hot t-butylbenzene, which are deesterified by the treatment with hot hydrobromic acid. Compounds 2 undergo replacement reactions towards some electrophiles at positions C-3, C-11, and C-7 (in that order).

Cycloaddition of 5-aryl-3-methylimidazo[5,1-b]thiazoles with dialkyl acetylenedicarboxylate in an aprotic nonpolar solvent gives a number of products including epimeric thiazolo[2,3-c]benzimidazoles (3 and 4) [1:2-cycloadducts], epimeric 5,10b-ethenothiazolo[3′,2′:3,4]imidazo[1,5-a]-pyridines (5 and 6) [1:3-cycloadducts], and thiazolo[3′,2′:3,4]imidazo[1,2-a]pyridines [1:3-adducts]. At higher temperature, formation of the 1:2-cycloadducts is favored over the 1:3-adducts, whereas the latter predominates at room temperature. In an aprotic polar medium, the 1:3-cycloadducts (5 and 6) and tetraalkyl 6-arylpyridine-2,3,4,5-tetracarboxylates are substantially produced. Epimerization of 3 and 4 has been found to compete well with fragmentation to 4H-1,4-benzothiazine.

Cycloaddition of imidazo[2,1-b]thiazoles with dialkyl acetylenedicarboxylate follows dual courses depending on the polarity of the solvent, affording pyrrolo[2,1-b]thiazoles in an aprotic nonpolar solvent, or imidazo[1,2-a]pyridines and imidazo[3,4-a]pyridines, together with thiophenes, in an aprotic polar solvent. Thiazolo[3,2-a]benzimidazole and imidazo[2,1-b]benzothiazole were also found to react with the acetylenedicarboxylate to give pyrido[1,2-a]benzimidazole and pyrrolo[2,1-a]benzothiazole, respectively. The reactions would be accounted for in light of the Diels-Alder reaction in an aprotic nonpolar solvent and the 1,4-dipolar cycloaddition in an aprotic polar solvent.

2,3-Dibenzoylpyrrolo[2,1-b]benzothiazole (2) and 6,7-dibenzoylpyrrolo[2,1-b]thiazoles (5a–b) have been synthesized by utilizing the cycloaddition reactions of imidazo[2,1-b]benzothiazole and imidazo[2,1-b]thiazoles, respectively, with dibenzoylacetylene followed by the elimination of a nitrile from each of the cycloadducts. Heteroannelations to 2 and 5 have been achieved by their reactions with hydrazine, aminoacetonitrile, ethyl glycinate, and phosphorus pentasulfide. The annelations by the second and third reagents proceed fairly regioselectively. Facile dimerizations of thieno[3′,4′:3,4]pyrrolo[2,1-b]benzothiazole and thieno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles to be produced by the reactions with the last reagent are also described.

The reaction of 1-methyl-1-azaazulen-2(1H)-one (1a) with dimethyl acetylenedicarboxylate (DMAD) or dibenzoylacetylene (DBA) in refluxing acetonitrile gave 1,2-disubstituted azulene (2), 2-methylcyclopent[de]isoquinolin-3(2H)-ones, 1-methyl-1-azacyclopent[cd]azulen-2(1H)-ones, and 3-substituted 1-methyl-1-azaazulen-2(1H)-ones, whereas in refluxing t-butylbenzene, compound 2 and 6,8-etheno-1-methylcyclohepta[b]pyrrol-2(1H)-one were obtained as major products. The reactions proceeded periselectively depending on the temperature. 2-Hydroxy-1-azaazulene behaved as 1-azaazulen-2(1H)-one and the reaction with DMAD gave similar result as for 1a. The reaction of 2-amino-1-azaazulene with DMAD gave methyl 2,4a-dihydro-2-oxo-1,4a-diazabenz[a]azulene-4-carboxylate and tetramethyl 4,5-dihydro-1H-1,11-diazacyclohept[a]azulene-2,3,4,5-tetracarboxylate. The reaction of 2-mercapto-1-azaazulene with DMAD gave tetramethyl 4,4a-dihydro-4a-azabenz[a]azulene-1,2,3,4-tetracarboxylate in moderate yield. The reaction mechanisms o...

Cyclohepta[4,5]pyrrolo[1,2-a]imidazoles (1,3a-diazacyclopent[a]azulenes) (2) and cyclohept[d]imidazo[1,2-a]imidazoles (1,3a,9-triazacyclopent[a]azulenes) (6) were synthesized from 2-aminocyclohepta[b]pyrroles and 2-aminocycloheptimidazole, respectively, in moderate to good yields. Reactions of 2 and 6 with reactive acetylenes gave 2-azacyclohepta[ef]cycl[3.2.2]azines together with bis(1,3a-diazacyclopent[a]azuleno)[1,7]diaza[12]annulenes (4) and 2,3-diazacyclohepta[ef]cycl[3.2.2]azines together with bis(1,3a,9-triazacyclopent[a]azuleno)[1,7]diaza[12]annulenes (8), respectively. Reactions of 2 and 6 with electron deficient olefins gave 4 and 8, respectively. These reactions proceeded regioselectively via 1,10-dipolar intermediates.

Reactions of 2-hydrazino-1-azaazulenes with acetylacetone gave 2-(3,5-dimethyl-1-pyrazolyl)-1-azaazulenes. Cyclizations of diethyl (1-azaazulen-2-yl)hydrazinomethylenemalonates in refluxing t-butylbenzene or on silica gel gave 1,2,5a-triazacyclohept[a]azulen-5(2H)-ones.

Reaction of 2-aryl-2H-cycloheptathiazoles with dimethyl acetylenedicarboxylate gave dimethyl 2-aryl-3H-1-thia-2a-azacyclopent[cd]azulene-3,4-dicarboxylate, tetramethyl 6-phenyl-2,3,4,5-pyridinetetracarboxylate, and tetramethyl 5-[(thioaroyl)iminomethyl]-1,2,3,4-naphthalenetetracarboxylate.

Formerly-proposed structures, cyclopent[de]isoquinolin-3(4H)-ones, for ring contracted by-products obtained from 1-substituted cyclohepta[b]pyrrol-2(1H)-ones and acetylenes, were revised to benz[cd]indol-2(1H)-ones on the basis of spectroscopic analysis.

2-Chloro-3-ethoxycarbonylcyclohepta[b]-pyrrole reacts with the carbanions derived from active methylene compounds to give substitution products and/or addition products depending on the reaction conditions.

Cycloadditions of imidazo[2,1-b]thiazole and thiazolo[3,2-a]benzimidazole with dimethyl acetylenedicarboxylate follow dual courses producing pyrrolo[2,1-b]thiazoles in an aprotic nonpolar solvent or imidazo[1,2-a]pyridines in an aprotic polar solvent.

The transylidation reaction of methyl(triphenylphosphoranylidene)acetate with 2-chlorocyclohepta[b]pyrrole derivatives has been studied. 3,8-Disubstituted derivatives gave a transylidation product only, whereas 3-substituted derivatives afforded not only a transylidation products but also the compounds formed by the addition of ylide at C-8. 13C NMR spectra of the transylidation products are recorded in part.

Cycloheptimidazole reacted with electrondeficient olefins (e.g., ethyl acrylate or acrylonitrile) to give the regioselective [6+2] cycloadducts, which were readily dehydrogenated to give 2a,3-dihydro-1,2a-diazacyclopent[cd]azulenes.