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.     

Synthesis of hexahydroazonino[5,6-b]indoles from hexahydroazepino[4,3-b]-and-[3,4-b]indoles and activated alkynes

A reaction of substituted hexahydroazepino[4,3-b]-and-[3,4-b]indoles with activated alkynes was studied. A one-step method for the synthesis of isomeric hexahydroazonino[5,6-b]indoles different by positions of the double bond in the azonine ring was developed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2244–2250, November, 2007.     

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.     

Selenium heterocycles. XXXIII. Synthesis of thieno[3,4-b]furan,seleno[3,4-b]furan,thieno[3,4-b]indole and seleno[3,4-b]indole. four novel heterocycles

Starting from the readily available 2-methyl-3-benzoylfuran, 1-phenylthieno[3,4-b]furan and 1-phenyl-seleno[3,4-b]furan were prepared. Also, starting from phenyl 3-methylindol-2-yl ketone and aryl 2-methyl-indole-3-yl ketones a series of substituted thieno[3,4-b]indoles and substituted seleno[3,4-b]indoles were prepared.     

2,3,4,9-Tetrahydro-1H-pyrido[3,4-b]indoles. II. Reversible transformation of 1-alkyl-2-(4,9-dihydro-3H-pyrido[3,4-b]indol-1-yl)cyclohexanol into 1-alkylidene-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indoles

Treatment of 2-(4,9-dihydro-3H-pyrido[3,4-b]indol-1-yl)-1-methylcyclohexanol ( 2a ) with acetic anhydride or methyl isocyanate gave 2-acetyl-2,3,4,9-tetrahydro-1-(6-oxoheptylidene)-1H-pyrido[3,4-b]indole ( 3 ) or 1,3,4,9-tetrahydro-N-methyl-1-(6-oxoheptylidene)-2H-pyrido[3,4-b]indole-2-carboxamide ( 4 ), respectively. Simpler analogues, 1-alkyl-4,9-dihydro-3H-pyrido[3,4-b]indoles, 7 , subjected to identical reaction conditions, gave 2-acetyl-1-alkylidene-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indoles 8 and 1,3,4,9-tetrahydro-N-methyl-1-alkyli-dene-2H-pyrido[3,4-b]indole-2-carboxamides 9 , respectively. A limited lanthanide shift reagent study to determine stereochemical assignments was also performed.     

Synthesis of 1H-[1,2]diazepino[4,5-b]indole derivatives

A synthesis of four 1H-[1,2]diazepino[4,5-b]indole derivatives and some preliminary information about their biological activity are presented. The starting materials were 2-ethoxycarbonylindoles and 2-ethoxy-carbonyl-3-formylindoles, la, b and 2a, b, respectively. 2-Ethoxycarbonyls la, b reacted with 1-dimethylamino-2-nitroethylene and -2-ethoxycarbonyl-3-formylindoles 2a, b in the presence of nitroalkanes (nitromethane or nitroethane) giving 3-(2-nitrovinyl)indoles 3a, b. Reduction of 3a, b yielded β-(2-oxoalkyl)indoles 4. On reaction with an excess of hydrazine hydrate, compounds 4 gave satisfactory yields of 5-oxo-1H-[1,2]diazepino[4,5-b]indoles 5.     

Indole esters as heterocyclic synthons. III. Preparation and reactions of furo[3,2-b]indoles

The preparation of furo[3,2-b]indoles via Dieckmann cyclization is described. The precursor diesters were obtained from 3-hydroxy-1H-indole-2-carboxylic acid esters and methyl or ethyl bromoacetate. Reactions of the furo[3,2-b]indole enolic esters prepared are discussed.     

Synthesis of 4H-furo[3,2-b]indoles. II. Bromination,acylation and nitration of 4H- and 4-benzoylfuro[3,2-b]indoles

Monobromination and monoacylation at the 2-position of 4H-furo[3,2-b]indole ring (III) were facilitated by the benzoyl group in the 4-position; subsequent nitration attempts were unsuccessful.     

Novel pyrano[3,2-b]indole derivatives: synthesis and some properties

Acid treatment of β-(3-acetoxyindol-2-yl)-α-cyanoacrylic acid derivatives (ethyl ester and nitrile) with aqueous or gaseous HCl afforded novel 3-substituted 2-oxo-2,5-dihydropyra-no[3,2-b]indoles. 2-Oxo-2,5-dihydropyrano[3,2-b]indole-3-carbonitrile was converted into ethyl 2-oxo-2,5-dihydropyrano[3,2-b]indole-3-carboximidate.     

Sur quelques analogues fluores des [1] benzothiopyrano[4,3-b]indoles et des 6H[1] benzothiopyrano[4,3-b] quinoleines

2-, 3-, and 4-Fluorinated analogs of the carcinogenic [1]-benzothiopyrano[4,3-b]indoles and of 6H[1]benzothiopyrano-[4,3-b]quinolines have been synthesized from the corresponding fluorothiochromanones. Nmr spectral data (at 60 Mc) of the six base molecules are reported. Biological tests for the possible carcinogenic activity of these new compounds, currently under way, have already shown one of them to be a powerful sarcomagen.     

Synthesis of substituted 3-amino-4-cyano-1-oxo-1,2,5,10-tetrahydroazepino [3,4-b]indoles

The preparation of 3-amino- and 3-dialkylamino-4-cyanoazepino[3,4-fc]indoles bearing substituents on the aromatic nucleus and N¹⁰ is outlined. Starting from suitable substituted ethyl 3-formylindole-2-carboxy-latcs 2 , condensation with malononitrile ( 3 ) and subsequent sodium borohydride-reduction yielded ethyl 3-(2,2-dicyanoethyl)indole-2-carboxylates 5 and 19 , respectively, which were cyclized in boiling alkoxides to 3-alkoxy-4-cyanoazepino[3,4-b]indoles 10,11,20 and 21 . This sequence constitutes a novel and flexible route to functional azepino[3,4-b>]indoles. The aminolysis of 10,11,20 and 21 with different amines and ammonia yielded the title compounds which were screened for their possible biological activity.     

Synthesis of functional 2-substituted 4-phenyl-9H-pyrimido[4,5-b]indoles

A method was developed for the synthesis of 2-oxo-4-phenyl-2,3-dihydro-9H-pyrimido[4,5-b]indole as well as of 2-chloro- and 2-nitramino-4-phenylpyrimido[4,5-b]indoles. The replacement of the chlorine atom in 2-chloropyrimidoindole gave rise to a number of its functional derivatives (morpholino, azido, and cyano). The reaction of 2-chloro-substituted pyrimidoindole with hydrazine hydrate and catalytic hydrogenation of 2-nitraminopyrimidoindole were studied.     

A reinvestigation of the synthesis of 3H-[1,2]diazepino[5,6-b]indoles. The synthesis of pyrido[4,3-b]indoles

Recently reported [1] syntheses of 6-methyl-1,2,4,5-tetrahydro-1,4-dioxo-3H[1,2]diazepino[5,6-b]indole ( 5 ) and 4-hydroxy-6-methyl-3H[1,2]diazepino[5,6-b]indole ( 12 ) were reinvestigated and shown to be in error. The correct assignments for these respective structures are 3-amino-1,9-dihydro-9-methyl-2H-pyrido[4,3-b]indol-2,4(3H)-dione ( 6 ) and 3-amino-3,9-dihydro-9-methyl-2H-pyrido[4,3-b]indol-2-one ( 13 ). Condensation of 6 and 13 with p-nitrobenzaldehyde produced benzylidene derivatives, which confirmed the presence of the amino groups.     

Synthesis of vinca alkaloids and related compounds LXXXV. Studies with azepino[3,4-b]indoles

The synthesis of some new pyrido[1′,2′:1,2]azepino[3,4-b]indoles starting from indole-3-propanamine 1 is described. Stereochemistry and observed side reactions are discussed.     

Synthesis and properties of [1,4]diazepino[6,5-b]indoles

1-Aryl-2-oxo-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole N-oxides were synthesized based on 3-(N"-aryl-N"-chloroacetyl)amino-2-formylindoles. Deoxidation of 2-oxo-1-phenyl-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole N-oxide afforded 1,2,3,6-tetrahydro- and 1,2,3,4,5,6-hexahydro[1,4]diazepino[6,5-b]indole derivatives. A new approach to the synthesis of pyrido[3,2-b]indole and pyrimido[5,4-b]indole derivatives was developed.     

Synthesis of 3-substituted cyclopenta[b]indoles

When reacting with I₂, 2-(cyclopent-2-enyl)anilines undergo cyclization into 3-iodo-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indoles in high yields. The minor reaction products were 3,5- or 3,7-diiodoindolines. Ammonolysis of 3-iodo-5-methyl-1,2,3,3a,4,8b-hexahydro-cyclopenta[b]indole or itsN-chloroacetyl derivative results in 3-amino-5-methyl-1,2,3,3a,48b-hexahydro- and 5-methyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles. Published inIzvestiya Akademii Nauk. Seriya Khimischeskaya, No. 10, pp. 1789–1793, October, 2000.     

Furopyridines. XXV. Synthesis of 5-substituted furo [2,3-b]pyridines

Derivatives ( 2–8 ) of furo[2,3-b]pyridine having a substituent at the β-position to the ring nitrogen were prepared from the 5-nitro compound 1 via the Sandmeyer reaction.     

Electrosynthesis of Dihydropyrano[4,3-b]indoles Based on a Double Oxidative [3+3] Cycloaddition

Oxidative [3+3] cycloadditions offer an efficient route for six-membered-ring formation. This approach has been realized based on an electrochemical oxidative coupling of indoles/enamines with active methylene compounds followed by tandem 6π-electrocyclization leading to the synthesis of dihydropyrano[4,3-b]indoles and 2,3-dihydrofurans. The radical–radical cross-coupling of the radical species generated by anodic oxidation combined with the cathodic generation of the base from O₂ allows for mild reaction conditions for the synthesis of structurally complex heterocycles.     

Synthesis of 4-hydrazino-5H-pyrimido[5,4-b]indole and related compounds

This paper describes the synthesis of two 4-amino-5H-pyrimido[5,4-b]indoles 5 , 4-hydrazino-5H-pyrimido[5,4-b]indole 6 , two 1,2,4-triazolo[4,3-c]pyrimido[5,4-b]indoles 8 , and tetrazolo[4,5-c]pyrimido[5,4-b]indole 10 . Starting with ethyl 3-aminoindole-2-carboxylate 1 , 5H-pyrimido[5,4-b]indol-4-one 2 was obtained (80%) by condensing with formamide. Reactions of 2 with phosphorus oxychloride and phosphorus pentasulfide gave respectively, 4-chloro-5H-pyrimido[5,4-b]indole 3 (70%) and 5H-pyrimido[5,4-b]indole-4-thione 4 (80%). Compound 3 reacted with amines (morpholine, piperidine) to give the respective 4-amino-5H-pyrimido[5,4-b]-indoles 5 , and compound 4 reacted with hydrazine to give 4-hydrazino-5H-pyrimido[5,4-b]indole 6 (80%). Two hydrazones of 6 (benzylidene, isopropylidene) 7 were also prepared (90%). Compound 6 reacted with formic and acetic acids to give (65–75%) the respective 1,2,4-triazolo[4,3-c]pyrimido[5,4-b]indoles 8 and with nitrous acid to give tetrazolo[4,5-c]pyrimido[5,4-b]indole 9 (85%). All the new compounds 2 to 9 were characterized by elemental analysis and spectral data (ir, nmr).     

Furopyridines. XIX. Reaction of furo[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridine with acetic anhydride

Acetoxylation of N-oxide of furo[2,3-b]- 2a , -[3,2-b]- 2b , -[2,3-c]- 2c and -[3,2-c]pyridine 2d with acetic anhydride afforded compounds substituted normally at the α- or γ-position to the ring nitrogen, 3a, 4a, 4b, 3d, 4d, 8 and 9 , and in addition compounds substituted on the furan ring, 5a, 6a, 5b, 6b, 7b, 5c and 7c which were unexpected compounds. The structures of these compounds were established from the ir, nmr and mass spectra, and x-ray crystal analysis of 5b .