Formylation of Furyl-substituted Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine and Imidazo[2,1-b]thiazole

Vilsmeier formylation of 2-(2-furyl)-substituted imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, and also 6-(2-furyl)imidazo[2,1-b]thiazole with 1 mole of reagent occurs at the free position of the imidazole ring, while with an excess of the reagent it also occurs at the position 5 of the furyl group.     

A new method for the synthesis of [1,4]diazepino[6,5-b]indole derivatives

Reactions of 3-[(N-aryl-N-chloroacetyl)amino]-2-formylindoles with substituted anilines gave 1,4-diaryl-2-oxo-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indol-4-ium chlorides and those with 4-aminopyridine yielded 4-amino-1-(1-aryl-2-oxo-2,5-dihydro-1H-pyrido[3,2-b]indol-3-yl)pyridinium chlorides. Reduction of 1,2,3,6-tetrahydrodiazepinoindol-4-ium chlorides afforded the corresponding hexahydro derivatives. An alternative synthesis of 1-(4-nitrophenyl)-3-oxo-4-phenyl-1,2,3,4,5,6-hexahydro[1,4]diazepino[6,5-b]indole from 3-[N-(4-nitrophenyl)amino]-2-[(phenylimino)methyl]indole was developed. The method involves the following sequence of transformations: reduction, chloroacetylation, and intramolecular alkylation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2193–2199, December, 2006.     

New synthesis of benzo[b][1,6]naphthyridines and pyrido[4,3-b]benz[f]azepines from lactim ethers of 3,4-dihydrocarbostyril and 1H-2,3,4,5-tetrahydrobenz[b]azepin-2-one

Condensation of lactim ethers of 3,4-dihydrocarbostyril and 1H-2,3,4,5-tetrahydrobenz[b]azepin-2-one with malonodinitrile, cyanoacetamide, and ethyl cyanoacetate gave the corresponding 2-methylidene derivatives. Their reactions with dimethylformamide diethyl acetal followed by cyclization into benzo[b][1,6]naphthyridines and pyrido[4,3-b]benz[f ]azepines were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 995–1002, May, 2007.     

Formylation of 3,4-Dihydropyrrolo[1,2-a]pyrazines

Formylation of 3,4-dihydropyrrolo[1,2-a]pyrazines containing alkyl or aryl substituents at position 1 has been studied under the conditions of the Vilsmeier reaction. The direction of the reaction depends on the structure of 3,4-dihydropyrrolo[1,2-a]pyrazine starting materials. Formylation of 1-methyl-substituted 3,4-dihydropyrrolo[1,2-a]pyrazines occurs at the methyl group.     

Condensed Thienopyrimidines. 14. Synthesis of 10H-Thiopyrano[4',3':4',5']thieno[2',3':4,5]pyrimido[2,3-c]-1,2,4-triazines

Reaction of a substituted 2-aminothienothiopyran with methyl(phenyl) isothiocyanate, intramolecular cyclization of the obtained N'-methyl(phenyl) thioureido derivatives, and work up of the cyclization products with hydrazine hydrate gave 2-hydrazinodihydrothiopyranothienopyrimidines. Treatment of the latter with pyruvic acid gave the novel 10H-thiopyrano[4',3':4',5']thieno[2',3':4,5]pyrimido[2,3-c]-1,2,4-triazines.     

Syntheses and reactions of [1,3,4]thiadiazolo[3,2-a]pyrimidinone derivatives

5-Imino-6H-7-one, 7-amino-5-one and 5-isocyano-7-one derivatives of [1,3,4]thiadiazolo- and -[1,3]thiazolo-[3,2-a]pyrimidines were synthesized. 5-Isocyano-7-one derivatives were obtained by the reaction of the corresponding 5-imino-6H-7-ones with the Vilsmeier reagent in one step.     

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.     

Interaction of 7-Chloro-9-methylthio-3-phenylpyrimido[5,4-f][1,2,4]triazolo[3,4-b][1,3,4]thiadiazepine with Some Nucleophiles

The reactions of 7-chloro-9-methylthio-3-phenylpyrimido[5,4-f][1,2,4]triazolo[3,4-b][1,3,4]thiadiazepine (1) with some nucleophiles have been studied. Substitution of the chlorine atom with hydrogen occurs with ammonia in DMSO to give 9-methylthio-3-phenylpyrimido[5,4-f][1,2,4]triazolo[3,4-b][1,3,4]thiadiazepin-7(8H)-one. With a methanolic solution of ammonia the 7-methoxy derivative is formed. Reaction of compound 1 with an excess of sodium methoxide in methanol gave 6,7-dimethoxy-9-methylthio-3-phenyl-5,6-dihydropyrimido[5,4-f][1,2,4]triazolo[3,4-b][1,3,4]thiadiazepine. The corresponding 7-substituted derivatives were obtained when compound 1 was heated with morpholine or 2-(dimethylamino)ethylamine. The azomethine bond of the thiadiazepine ring is reduced by sodium borohydride to give the corresponding 5,6-dihydro derivatives.     

The reactions of 2,2-difluoro-4-methylnaphtho[l,2-e]-1,3,2-dioxaborin and its [2,1-e]isomer with N,N-dimethylformamide

The title compounds react with dimethylformamide in acetic anhydride to give dimethylamino-vinyl derivatives which, on treatment with base, yield benzochroman-4-ones. The [1,2-e] isomer reacts with the Vilsmeier complex to give 3-formylbenzo[f]chrom-4-one and 9-hydroxy-1-phenalenone, and the [2,1-e]isomer gives 3-formylbenzo[h]chrom-4-one.     

Synthesis of [1,2,3]Triazolo[5,1-a]isoquinoline Derivatives via a Selective Cascade Cyclization Sequence of 1,2-bis(Phenylethynyl)benzene Derivatives

A direct, concise, synthetic method for the generation of [1,2,3]triazolo[5,1-a]isoquinoline derivatives, using a selective cascade cyclization of unsymmetrical substituted 1,2-bis(phenylethynyl)benzene derivatives with NaN₃, has been developed. The reaction gave different substituted [1,2,3]triazolo[5,1-a]isoquinolines in moderate to good yields. It was found that the substituents on the alkynes were important for the selectivities of the cascade cyclization sequences.     

Synthesis of Pyrrolo[a]- and Pyrrolo[c]phenanthridine Derivatives and Indolinyl and Indolylsubstituted 6-Phenanthridines

The corresponding Mannich bases have been synthesized by the aminomethylation of 6-methyl-1H-pyrrolo[2,3-a]- and 4-methyl-3H-pyrrolo[3,2-c]phenanthridinium iodides. The interaction of 6-chloro-phenanthridine with indoline and with 5-amino-N-acetylindoline gave the corresponding derivatives of phenanthridine. 6-(1-Indolyl)phenanthridine has been obtained by the dehydrogenation of 6-(1-indolinyl)phenanthridine with manganese dioxide.     

Fluorinated benzimidazo[1,2-a]quinolones

The reactions of 2-cyanomethylbenzimidazole with polyfluorobenzoyl chlorides afforded 2-(1,3-dihydrobenzimidazol-2-ylidene)-3-oxo-3-polyfluorophenylpropionitriles. Refluxing of the latter compounds in acetonitrile in the presence of DBU or in dimethylformamide in the presence of amines gave rise to fluorine-containing derivatives of benzimidazo[1,2-a]quinolone.     

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.     

Cesium Complex of an Unsymmetrical Calix[4]crown-dibenzocrown-6

An unsymmetrical calix[4]-bis-crown ether having both conventional crown-6 and dibenzocrown-6 rings in a fixed 1,3-alternate conformation was synthesized with good yield by the reaction of a monocyclic calix[4]crown-6 with dibenzodimesylate in the presence of cesium carbonate. The cesium ion selectivity among alkali metal ions increased compared to symmetrical calix[4]-bis-crown-6. The solid state structureof the ligand-cesium complex illustrates a 1:2 complex ratio. On the contrary, insolution, e.g., extraction equilibrium and ¹H NMR experiment gave a 1:1 complex ratio. From the result of the chemical shift change upon metal ion complex, the cesium ion seems to prefer the dibenzocrown loop to the conventional crown-6 ring.     

Benzo[b]tellurophene, Dibenzo[b,d]tellurophene, and Their Derivatives. (Review)

Data on the synthesis, reactions, crystal structure, and spectral characteristics of benzo[b]tellurophene, dibenzo[b,d]tellurophene, and their derivatives are reviewed and analyzed.     

Synthesis of pyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazolo[4,3-<Emphasis Type="Italic">c</Emphasis>]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

Green Method for the Synthesis of Benzo[f]pyrimido[4,5-b]quinoline Derivatives Catalyzed by Iodine in Aqueous Media

A convenient one-pot synthesis of benzo[f]pyrimido[4,5-b]quinoline derivatives is described via three-component reaction of benzaldehydes, naphthalen-2-amine, and barbituric acid at room temperature in aqueous media catalyzed by iodine. Compared with other methods, this three-component reaction used a green solvent, gave good yields, and was operationally simple.     

Synthesis of derivatives of a new heterocyclic system pyrazolo[3,4-b]pyrido[1′,2′: 1,2]imidazo[4,5-d]pyridine

1-[4-Aminoarylpyrazolo[3,4-b]pyridin-5-yl]pyridinium chlorides undergo cyclization under reflux in tert-butanol in the presence of an excess of potassium tert-butoxide to form tetracyclic derivatives of pyrazolo[3,4-b]pyrido[1′,2′:1,2]imidazo[4,5-d]pyridine. The reaction scheme of the processes is proposed. The structures of the reaction products were confirmed by physicochemical methods. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 710–714, April, 2006.     

Synthesis and Properties of Substituted Isoxazolo[3',4':4,5]thieno[2,3-b]pyridines

We synthesized derivatives of a novel heterocyclic system, isoxazolo[3',4':4,5]thieno[2,3-b]pyridine by sequential conversions in three steps: isomerization of 2-(2-R-ethylthio-2-oxo)-3-pyridyl cyanides obtained by alkylation from substituted 3-cyano-2(1H)-pyridinethiones by -halomethyl ketones in alkaline medium, to form 3-aminothieno[2,3-b]pyridines; diazotization of the amino group followed by nucleophilic substitution of the diazonium group by an azido group, bypassing the step of isolating the diazonium salts; and thermolysis of the azides formed.     

2-[3-(Trifluoromethyl)phenyl]furo[3,2-b]pyrroles: synthesis and reactions

The synthesis and reactions of methyl 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole-5-carboxylate (1a) are described. Upon reaction with methyl iodide, benzyl chloride, or acetic anhydride, this compound gave N-substituted products 1b-d. By hydrolysis of compounds 1a-c, the corresponding acids 2a-c were formed, or by reaction with hydrazine-hydrate, the corresponding carbohydrazides 3a-c were formed. By heating 2-[3-(trifluoromethyl)phenly]-4H-furo[3,2-b]pyrrole-5-carboxylic acid (2a) in acetic anhydride, 4-acetyl-2-[3-(trifluoromethyl)phenyl]furo[3,2-b]pyrrole (4) was formed. By hydrolysis of 4, 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole (5a) was formed, and reactions with methyl iodide or benzyl chloride gave N-substituted products 5b-c. The reaction of 4 with dimethyl butynedioate gave substituted benzo[b]furan 6. Compound 3a reacted with triethyl orthoesters giving 7a-c, which afforded with phosphorus (V) sulphide the corresponding thiones 8a-c. The thiones 8a-c reacted with hydrazine hydrate to form hydrazine derivatives 9a-c. The reaction of triethyl orthoformiate with compounds 9a-c led to furo[2′,3′: 4,5]pyrrolo[1,2-d][1,2,4]triazolo[3,4-f][1,2,4]triazines 10a-c. Hydrazones 11a-c were formed from 3a-c and 5-[3-(trifluoromethyl)phenyl]furan-2-carboxaldehyde. The effect of microwave irradiation on some condensation reactions was compared with “classical” conditions. The results showed that microwave irradiation shortens the reaction time while affording comparable yields.