Synthesis of 3-methyl-[1,2,4] -triazepino[6,5,4-jk] carbazol-4(3H)one

The title compound ( 14 ), a representative of a novel ring system, was prepared from 9H-carbazole-1-carboxylic acid 1-methylhydrazide ( 7 ) and triethyl orthoformate. Attempted cyclization of 7 with triethyl orthoacetate led only to 9H-carbazole-l-carboxylic acid 2-(l-ethoxyethylidene)-l-methylhydrazide ( 16 ). Treatment of 16 with trifluoroacetic acid gave 9H-carbazole- 1 -carboxylic acid ( 12 ). A postulated mechanism for this transformation was supported by studies with model compounds. A new synthesis of 1 -benzoyl-2-methylhydrazine ( 24 ), using 1-acetyl-1-methylhydrazine ( 22 ) as a synthon, is described.     

Furopyridines. V. A simple synthesis of furo[2,3-c]pyridine and its 2-and 3-methyl derivatives

A simple synthesis of furo[2,3-c]pyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxyisonicotinate ( 2 ) is described. The hydroxy ester 2 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 3a or 3b . Cyclization of compound 3a afforded ethyl 3-hydroxyfuro [2,3-c]pyridine-2-carboxylate ( 4 ) which was hydrolyzed and decarboxylated to give furo[2,3-c]pyridin-3(2H)-one ( 5a ). Cyclization of 3b gave the 2-methyl derivative 5b . Reduction of 5a and 5b with sodium borohydride yielded the corresponding hydroxy derivative 6a and 6b , respectively, which were dehydrated with phosphoric acid to give furo[2,3-c]pyridine ( 7a ) and its 2-methyl derivative 7b . 4-Acetylpyridin-3-ol ( 8 ) was O-alkylated with ethyl bromoacetate to give ethyl 2-(4-acetyl-3-pyridyloxy) acetate ( 9 ). Saponification of compound 9 , and the subsequent intramolecular Perkin reaction gave 3-methylfuro[2,3-c]pyridine ( 10 ). Cyclization of 9 with sodium ethoxide gave 3-methylfuro[2,3-c]pyridine-2-carboxylic acid, which in turn was decarboxylated to give compound 10 .     

Synthese und thermisches Verhalten von 6,8-Dimethylentricyclo[3.2.1.02,7]oct-3-enen; [3s 3s]-sigmatropische Umlagerungen von 6-Allenyl- und 6-Propargly-1- Methylen-cyclohexa-2,4-dienen in aromatische Kohlenwasserstoffe als Beispiele für konzertierte Semibenzol → Benzol-Umlagerungen

The tricyclic dimethylene hydrocarbons 5 , 6 , 7 , 8 and d₂- 5 , (Scheme 2), which are prepared by Wittig-reaction from the corresponding ketones, are rearranged, by heating, to 4-aryl-but-1-yne derivatives via the unstable 6-allenyl-1-methylene-cyclohexa-2, 4-diene intermediates (e.g. Scheme 14). Using the deuterium-labelled compound d₂- 5 , it was shown that the allenyl moiety, formed by a retro-Diels-Alder reaction (cycloreversion) of the tricyclic dimethylene compound, migrates with complete inversion in the final o-semibenzene-benzene rearrangement (Schemes 11 and 14). Reaction of 6-propargyl-cyclohexa-2, 4-dien-1-ones with triphenylphosphonium methylide gives 6-propargyl-1-methylene-cyclohexa-2 4-dienes, which immediately undergo a [3s, 3s]-rearrangement to form 4-aryl-buta-1, 2-dienes (Scheme 9). In contrast, the rearrangement of the corresponding 4-propargyl-1-methylene-cyclohexa-2, 5- dienes proceeds by a radical mechanism (Schemes 10 and 13).     

1a,11b-dihydrobenz[5,6]anthr[1,2-B]azirine. A non k-region polycyclic arene imine

The synthesis of the title compound 9 is described. Benz[a]anthracene 8,9-oxide (6) was reacted with sodium azide in aqueous acetone and the trans-9-azido-8,9-dihydrobenz[a]anthr-8-ol (7), so formed, was cyclized by tri-n-butylphosphine. Attempts to dehydrogenate 10,11-dihydrobenz[a]anthracene 8,9-imine (4) with DDQ or by allylic bromination followed by base assisted dehydrobromination was unsuccessful. The N-tosyl derivative of 4, prepared from the free imine, N,O-bis(trimethylsilyl)acetamide and tosyl chloride underwent rapid aziridine-ring cleavage by the silylating agent to give trans-8,9,10,11-tetrahydro-8-(4-methyl)benzensulfon-amido-9- [(trimethyl)oxy]benz[a]anthracene (10).     

Heterotricyclodecane XXVII. Ein weiterer Zugang zu 2,6-Dioxatricyclo [3.3.2.03,7]decan

A Further Approach to 2,6-Dioxatricyclo[3.3.2.0^3,7]decane A further synthesis of 2,6-dioxatricyclo[3.3.2.0^3,7]decane ( 10 ) is described by bridging the 9-oxabicyclo[4.2.1]non-7-en-3endo-ol ( 9 ). The latter compound was prepared by ring expansion starting from the known 8-oxabicyclo[3.2.1]oct-6-en-3-on ( 1 ).     

Furopyridines. III. A new synthesis of furo[3,2-b]pyridine

A convenient synthesis of furo[3,2-b]pyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxypiconate ( 1 ) is described. The hydroxy ester 1 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 2a or 2b . Cyclization of compound 2a afforded ethyl 3-hydroxyfuro[3,2-b]pyridine-2-carboxylate ( 3 ) which in turn was hydrolyzed and decarboxylated to give furo[3,2-b]pyridin-3-(2H)-one ( 4a ). Cyclization of 2b gave the 2-methyl derivative 4b . Reduction of 4a and 4b with sodium borohydride yielded the corresponding hydroxy derivative 5a and 5b respectively, which were dehydrated with phosphoric acid to give furo[3,2-b]pyridine ( 6a ) and its 2-methyl derivative ( 6b ). 2-Acetylpyridin-3-ol ( 8 ) was converted to the ethoxycarbonylmethyl ether ( 9 ) by O-alkylation with ethyl bromoacetate, which was cyclized to give 3-methylfuro[3,2-b]pyridine-2-carboxylic acid ( 10 ). Decarboxylation of 10 afforded 3-methylfuro[3,2-b]pyridine ( 11 ).     

Research on nitrogen containing heterocyclic compounds. XIX: Synthesis of 8H-imidazo[2,1-c]-s-triazolo[4,3-a]-[1,4]benzodiazepine and its 1-derivatives

Reaction of 2-nitrobenzyl iodide with 1H-imidazole, in the presence of potassium tert-butoxide and 18-crown-6, gave 1-(2-nitrobenzyl)-1H-imidazole. Trichloroacetylation of this compound furnished trichloroacet-ylimidazole 8 , which on treatment with sodium ethoxide was transformed into the corresponding ethoxycarbonyl derivative 9 . Catalytic reduction of the nitro group to the amino group yielded 10 , which was then cyclized to 10,11-dihydro-11-oxo-5H-imidazo[2,1-c][1,4]benzodiazepine 11. Treatment of this lactam with di-4-morpholinylphosphinic chloride followed by reaction of the intermediate 12 with formylhydrazine gave the title compound or its 1-derivatives when acetylhydrazine or isonicotinoylhydrazine were used instead of formylhydrazine.     

[1]Benzofuro[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine synthesis and coordination reactions

(E)-3-(1-Benzofuran-2-yl)propenoic acid (1) was prepared from 1-benzofuran-2-carbaldehyde under the Doebner’s conditions. The obtained acid was converted to the corresponding azide 2, which was cyclized by heating in diphenyl ether to [1]benzofuro[3,2-c]pyridine-1(2H)-one (3). This compound was aromatized with phosphorus oxychloride to chloroderivative 4 which was reduced with zinc and acetic acid to the title compound 5. [1]Benzofuro[3,2-c]pyridine-2-oxide (6) was synthesized by reaction of 5 with 3-chloroperoxybenzoic acid in dichloromethane. Treatment of 6 with benzoyl chloride and potassium cyanide (Reissert-Henze reaction) was shown to produce the corresponding [1]benzofuro[3,2-c]pyridine-1-carbonitrile (7). The title compound was used for preparation of complexes Cu₂(ac)₄(bfp)₂ (8) and CoCl₂(bfp)₂ (9), where ac=CH₃CO₂⁻ and bfp=[1]benzofuro[3,2-c]pyridine. Both oxygen atom of carboxylate ions is used in the coordination to Cu(II). Thermal properties of the complexes 8 and 9 have been studied by TG and DTA and both complexes exhibited high thermal stability while complex 9 are thermally more stable than complex 8.     

The synthesis of 11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles,11H-tetrazolo[4,5-b]pyridazino[4,5-b]indoles and 1,2,4-triazolo[3,4-f]-1,2,4-triazino[4,5-a]indoles

This paper describes the synthesis of the previously unknown 11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles (2) and 11H-tetrazolo[4,5-b]pyridazino[4,5-b]indoles (3) from 4-hydrazino-5H-pyridazino[4,5-b]indoles (1) , as well as the synthesis of 1,2,4-triazolo[3,4-f]-1,2,4-triazino-[4,5-a]indoles (10) from 2-indolecarbohydrazide (4) . Compounds 2 were obtained by acylation of compounds 1 , followed of thermal cyclization and compounds 3 by treating compounds 1 with nitrous acid. The reactions of compound 4 with formic acid or ethyl orthoformiate gave 1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indole (6) . Treating this last compound with phosphorus oxychloride or phosphorus pentasulfide, followed by hydrazine, gave 1-hydrazino-1,2,4-triazino-[4,5-a]indole (9) . Acylation of this last compound, followed of cyclization gave compounds 10 . All the compounds were characterized by elemental analysis and ir and ¹H-nmr spectra.     

Nitrogen bridgehead compounds. Part 88. Synthesis of 3H, 7H-[1,4]diazepino[3,4-b]quinazoline-3,7-diones

3H,7H-[1,4]Diazepino[3,4-b]quinazolone-3,7-diones 9, 11 were synthesized starting from 2-(1-bromo-ethyl)quinazolin-4(3H)-ones 3 and 17 via 2-[1-(4-methoxyphenylamino)ethyl]quinazolin-4(3H)-ones 4 and 18. Cyclization of 3-[2-(1-bromoethyl)-4-oxo-3,4-dihydroquinazolin-3-yl)propionic acid 14 by the action of triethylamine provided the first representative of the tricyclic 7H-[1,4]oxazepino[3,4-b]quinazoline-3,7-dione system, compound 15. The new tricyclic derivatives 9, 11 and 15 are characterized by uv, ir and ¹H nmr spectroscopy.     

The synthesis of benzofuroquinolines. IV. Some halobenzofuro[2,3-B]- and [3,2-C]quinoline derivatives

Some 8- or 9-halobenzofuro[2,3-b]quinolines ( 1a , 8-F, 8-C1, 9-F, 9-Cl) and 9-halobenzofuro[2,3-b]quinoline-11-carboxylic acid ( 1b , F, Cl) were synthesized from 6- or 7-halo-3-(2-methoxyphenyl)-2-oxo-1,2-dihydroquino-line-4-carboxylic acids ( 3 ). And, some 9-halo-11(6H)-benzofuro[2,3-b]quinolinone ( 8 , F, Cl, Br) and 2-halo-6(5H)-benzofuro[3,2-c]quinolinone ( 9 , F, Cl, Br) were synthesized from 6-halo-4-hydroxy-3-(2-methoxyphenyl)-2(1H)-quinolinone ( 7 ), and they were converted to the corresponding chlorohalobenzofuroquinolines ( 1c , 9-F, 9-C1, 9-Br, and 2 , F, Cl, Br).     

Condensed benzopyrans. IV. Synthesis of some derivatives of 7H- and 9H-pyrano[3,2-E]indoles

The hydrazones derived from coumarin-6-ylhydrazine and ethyl 6-hydrazinochromone-2-carboxylate undergo facile indolization to give 3H,7H-pyrano[3,2-e]indol-7-ones (IIIb-IIIg) and ethyl 9-oxo-3H,9H-pyrano[3,2-e]indole-7-carboxylates (IVb-IVd), respectively, in good yields. Compounds IVb-IVd are derivatives of a new ring system.     

Heterocycles from amino acids. A novel synthetic approach for imidazo[1,5-a]pyridines and imidazo[1,5-a]quinolines

From the corresponding heterocyclic amino acids 2 and 9a the heterocyclic systems imidazo[1,5-a]pyridine ( 3 ) and imidazo[1,5-a]quinoline ( 10 ) are easily accessible. From compound 7 the tricyclic system 11 was prepared and from compound 17a a pyridyl-1,2,4-triazinone ( 18 ) could be obtained.     

Synthesis of 1H-pyrazino[1,2-a]pyrido[2,3-e]pyrazine and 2H-Pyrano[2,3-b]pyrido[2,3-e]pyrazine Derivatives

With a continuing interest on heteropolycyclic structures which may show biological activities, we synthesized new tricyclic derivatives in which the pyridopyrazine skeleton is fused with pyrazine 7 and 8, B , n = 1. However, the initial design of obtaining also the cyclohomologous structure B (n = 2) produced instead a pyranopyridopyrazine derivative 11 . Thus during the attempt to prepare a pyridodiazepine intermediate, beside a very small amount of the desired product 10 , the pyridopyrazine 9 was obtained. The latter compound reacted with chloroacetyl chloride/chloroketene to give 4-carbethoxy-10-(chloroacetyl)-5,10-dihydro-5-methyl-2H-pyrano[2,3-b]pyrido[2,3-e]pyrazin-2-one ( 11 ). In studying the behavior of this derivative, compounds 12–14 were obtained. Compounds 4b,c, 5a,b, 7, 8, 9 and 14 have been submitted to preliminary pharmacological screening as CNS depressant agents.     

Die Dienol-Benzol-Umlagerung von Propargylcyclohexadienolen: aromatische [1,2]-, [3,3]- und [3,4]-sigmatropische Umlagerungen

The acid catalysed dienol-benzene rearrangement of methyl substituted o- and p-propargylcyclohexadienols ( 18–22 , 34 and 35 ) was investigated. In the first step water is eliminated to yield the corresponding methyl propargyl benzonium ions (cf. scheme 6, a ), which undergo [1s, 2s] sigmatropic rearrangements to give propargylbenzenes ( 28 , 29 , 30 , 38 ) and [3s, 4s] sigmatropic rearrangements to give allenylbenzenes ( 24–27 , 40) (cf. schemes 2, 3, 5, 6). [3s, 3s] sigmatropic rearrangements occur only to a small extend. In the rearrangement of 2-propargyl-2,4,6-trimethylcyclohexa-3,5-dien-1-ol ( 18 ) a [1s, 2s] sigmatropic methyl shift is observed (4%).     

Substituted 9-Oxabicyclo[4.2.1]- and 9-Oxabicyclo[3.3.1]nonanes (Part II)

The preparation, isolation, structure determination, and some reactions of the two stereoisomers of 2-iodo-9-oxabicyclo[4.2.1]nonane ( 9 and 10 ) and of 2-iodo-9-oxabicyclo[3.3.1]-nonane ( 11 and 12 ), respectively, are described. Iodine cleavage of the [4.2.1]-iodomercuri compound 3 yielded the iodides 9, 10 , and 11 , and iododemercuration of the [3.3.1]-iodomercuri compound 6 afforded the iodo compounds 9, 11 , and 12 , respectively. Direct treatment of 4-cycloocten-1-ol ( 1 ) with iodine in chloroform resulted in the exclusive formation of the two endo-iodides 9 and 11 . Raney nickel treatment as well as lithium aluminium hydride reduction of each índividual iodo compound 9, 10, 11 , and 12 gave the corresponding unsubstituted 9-oxabicyclononane ( 4 or 8 , respectively) with the unaltered skeleton. No rearrangement products could be observed. An oxonium ion is involved as an intermediate in the reaction of the endo-iodides 9 and 11 with silver acetate leading to an identical mixture of the two acetates 15 and 16 as well as in the isomerization of 9 to 11 .     

Structural study of 5-methoxyfuro[3,2-e]imidazo[1,2-c]pyrimidine

The nmr and X-ray diffraction data of the novel ring system furo[3,2-e]imidazo[1,2-c]pyrimidine are reported in this paper. The crystal and molecular structure of this compound (C₉H₇N₃O₂·1/2H₂O) has been solved at room temperature. Crystals are monoclinic in a space group of P2/n with cell constants a = 9.982(8), b = 13.526(9) and c = 13.981(9) Å, β = 107.44(5)°, V = 1800.9 ų, Z = 8, D_x = 1.462 Mg·m^?3. The structure was solved by full matrix least square refinement giving a final R = 0.054 (Rw = 0.069) for 1263 reflections (I>3.0σ(I)). The compound is essentially planar, existing in two slightly structural different forms, A and B. These are held in pairs with symmetry related molecules by hydrogen bonds formed with two water molecules. Then the dimeric units are stacked parallel to the c axis to form the tridimensional packing.     

Condensed 1,3-benzothiazinones. 1. Facile synthesis of 2-amino-1,2,4-triazolo[5,1-b][1,3]-benzothiazin-9-one

Treating 2-mercaptobenzohydrazide ( 1a ) with cyanogen bromide gave 3-amino-2-imino-3,4-dihydro-2.H-1,3-benzothiazin-4-one ( 2a ). This compound underwent further cyclocondensation with a second molecule of cyanogen bromide or S-methylisothiourea sulfate to afford the biologically interesting 2-amino-1,2,4-triazolo-[5,1-b][1,3]benzothiazin-9-one ( 3c ). Compound 3c could also be prepared directly from 1a by treating with excess amount of cyanogen bromide in more satisfactory yield.     

Pyridine N-sulfides. Benzisothiazolo[2,3-a]pyridinium tetrafluoroborates and benzothiopheno[3,2-b]pyridines. Novel heterocyclic systems

2-(2-Mercaptophenyl)pyridines are prepared from the corresponding phenols and oxidized with N-chloro-succinimide and silver tetrafluoroborate to benzisothiazolo[2,3-a]pyridine salts ( 4 ). The latter do not rearrange thermally or photochemically to benzothiopheno[3,2-b)pyridines ( 19 ) and are attacked by nucleophiles at sulfur rather than in the pyridine ring, to give the original 2-(2-mercaptophenyl)pyridine back in a reaction involving a dismutation. 19 is prepared by rearranging O-[2-(3-bromo-2-pyridyl)-4-nitrophenyl]dimethylthio-carbamate to the S-aryl compound and heating the latter with strong base.     

Macrocyclic Tetraethynylethene Molecular Scaffolding: Perethynylated aromatic dodecadehydro[18]annulenes,antiaromatic octadehydro[12]annulenes,and expanded radialenes

Tetraethynylethene (3,4-diethynylhex-3-ene-1,5-diyne) molecular scaffolding provided access to novel macrocyclic nanometer-sized C-rich molecules with unusual structural and electronic properties. Starting from cis-bis-deprotected cis-bis(trialkylsilyl)protected tetraethynylethenes, the per(silylethynyl)ated octadehydro[12]annulenes 1 and 2 and the corresponding dodecadehydro[18]annulenes 4 and 5 were prepared by oxidative Hay coupling. X-Ray crystal-structure analyses of (i-Pr)₃Si-protected 2 and Me₃Si-protected 4 showed that both annulene perimeters are perfectly planar. Electronic absorption spectral comparisons provided strong evidence that the macro rings in the deep-purple-colored 1 and 2 are antiaromatic (4n π-electrons), whereas those in yellow 4 and 5 are aromatic ((4n + 2) π-electrons). Although unstable in solution, the antiaromatic compound 2 gave high-melting crystals in which the individual octadehydro[12]annulene chromophores are isolated and stabilized in a matrix-type environment formed by the bulky (i-Pr)₃Si groups. Electrochemical studies demonstrated that the antiaromatic octadehydro[12]annulene 2 undergoes two stepwise one-electron reductions more readily that the aromatic chromophore 5 . This redox behavior is best explained by the formation of an aromatic (4n + 2) π-electron dianion from 2 , whereas 5 loses its aromaticity upon reduction. The Me₃Si derivative 4 was deprotected with borax in MeOH/THF to give the highly unstable hexaethynyl-dodecadehydro[18]annulene 6 , a C₃₀H₆ isomer and macrocyclic precursor to a two-dimensional all-C-network. Deprotection of 2 did not give isolable amounts of tetraethynyl-octadehydro[12]annulene 3 due to the extreme instability of the latter. Starting from dimeric and trimeric acyclic tetraethynylethene oligomers, a series of expanded radialenes were obtained. They possess large C-cores with silylethynyl-protected peripheral valences and can be viewed as persilylated C₄₀ ( 7 ), C₅₀ ( 8 ), and C₆₀ ( 9 ) isomers. These expanded C-sheets are high-melting, highly stable, soluble materials which were readily characterized by laser-desorption time-of-flight (LD-TOF) mass spectrometry. Due to inefficient macrocyclic cross-conjugation and/or non-planarity, the extent of π-electron delocalization in 7 – 9 is limited to the longest linearly conjugated π-electron fragment. In agreement with these properties, all three expanded radialenes exhibited similar redox behavior; they are difficult to oxidize but undergo several reversible one-electron reductions in similar potential ranges. Presumably, the reduced π-electron delocalization is also at the origin of the particularly high stability of 7 – 9 .