Research on heterocyclic compounds. XXIII. Phenyl derivatives of fused imidazole systems

The reaction of various heteroarylamines with ethyl 2-benzoyl-2-bromoacetate was used to obtain some imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, imidazo[2,1-b]thiazoles and imidazo[2,1-b]benzothiazoles characterized by the presence of a phenyl moiety on the imidazole ring. In the case of thiazole and benzothiazole derivatives, unexpected by-products were isolated and their structures elucidated.     

Cyclic isothioureido compounds. II. Reaction of trans-3a,4,5,9b-tetrahydronaphth[1,2-d]-imidazoline-2-thiones with α-bromoketones

The reaction of trans-3a,4,5,9b-tetrahydronaphth[1,2-d]imidazoline-2-thiones ( 8 ) with α-bromoketones gave, depending upon the structure of the α-bromoketones, reaction solvent and reaction temperature, the hydrobromides of tetrahydronaphth[1,2-d]imidazolin-2-ylthiomethyl ketone ( 10 ), hexahydro-8-hydroxynaphth[1′,2′:4,5]imidazo[2,1-b]thiazoles ( 5, 11, 19 and 20 ) or tetrahydronaphth[1′,2′:4,5]imidazo[2,1-b]-thiazoles ( 12 and 16 ). Structural determinations based on ir and nmr spectroscopies are discussed.     

Reactions of α-ketohydrazidoyl halides with some heterocyclic amines. Facile synthesis of arylazo derivatives of fused heterocycles with a bridgehead nitrogen atom

Arylazo derivatives of imidazo[2,1-b]thiazoles, imidazo[1,2-b]pyrazoles, imidazo[1,2-b]-s-triazoles, imidazo[1,2-a]pyrimidines, and imidazo[1,2-a]pyridines were obtained in good yields from α-keto hydrazidoyl halides and 2-aminothiazole, 5-aminopyrazole, 5-aminotriazole, 2-aminopyrimidine, and 2-aminopyridine, respectively (cf. Tables I and II). The structures of the products were assigned and confirmed on the basis of their elemental analyses, spectra, and alternate synthesis wherever possible.     

Preparation of 2-aryl and 2-aryloxymethyl imidazo[1,2-a]pyridines and related compounds

A series of substituted 2-aryl imidazo[1,2-a]pyridines has been prepared in which a variety of substituents are introduced on the 4′-position of the phenyl ring and on the 3, 5 , 6 or 7 position of the heterocyclic ring. Most examples have acetamido, bromo, cyano, or formyl substituents at the 4′-position. Analogous imidazo-[2,1-b]fhiazoles and imidazo[1,2-a]pyrimidines have also been prepared. Another series of compounds consisting of 4′-formylphenoxymethyl derivatives of imidazole, the three positional isomers of pyridine, thiazole, benzimidazole and ring-substituted imidazo[1,2-a]pyridines has been prepared. 2-(4′-Formylphenylethenyl) derivatives of imidazole and imidazo[1,2-a]pyridine were also prepared.     

Thermolyzed products of naphth[1,2-d]imidazo[2,1-b]-thiazole-2,3-dione

Themolysis of naphth[1,2-d]imidazo[2,1-b]thiazole-2,3-dione ( 1 ) in dimethylformamide gave an intermediate 2-isocyanatonaphtho[1,2-d]thiazole ( 2 ), which underwent [4 + 4] cyclodimerization to yield dinaphtho-[1″,2″:4,5;1′″,2′″:4′,5′]dithiazolo[3,2-a:3′,2′-e]-1,3,5,7-tetrazocine-9,19-dione ( 3 ). The possible [4 + 2] cycloadduct, 3-(2-naphtho-[1,2-d]-thiazolyl)naphtho[1′,2′:4,5]thiazolo[3,2-a]-1,3,5-triazine-2,4-dione ( 4 ), an usual dimer type of heterocyclic isocyanates was not produced. Discrimination between the two isomers was established on the basis of spectral analyses.     

Die Synthese von 2,3,4,5-1H-Tetrahydroimidazo[2,1-b]chinazolin-2,5-dionen und analogen 2,3,4,5-1H-Tetrahydroimidazo[1,2-a]thieno[2,3-d] (bzw. [3,2-d])-pyrimidin-2,5-dionen

The Synthesis of 2,3,4,5-1H-Tetrahydroimidazo[2,1-b]quinazolin-2,5-diones and analogous 2,3,4,5-1H-Tetrahydroimidazo[1,2-a]thieno[2,3-d] (or [3,2-d])-pyrimidin-2,5-diones The syntheses of various imidazo [2, 1-b]quinazolinediones and their thiophene analogs are described.     

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.     

Synthesis and some properties of N-unsubstituted pyrrolo[2,1-c]-1,3-diazacycloalkano[1,2-a]pyrazinones

Reactions of methyl 2-(2-formyl-1H-pyrrol-1-yl)alkanoates with unsubstituted aliphatic 1,2-, 1,3-, and 1,4-diamines gave N-unsubstituted pyrrolo[2,1-c]-1,3-diazacycloalkano[1,2-a]-pyrazinones. Some of them show ring-chain tautomerism. Transformations of these compounds led to a number of novel heterocyclic systems: 2,10-dihydro-3H,5H-imidazo[1,2-a]-pyrrolo[1,2-d]pyrazines, 2,3,4,11-tetrahydro-6H-pyrrolo[1??,2??:4,5]pyrazino[1,2-a]pyrimidines, 1,2,3,5,6,10b-hexahydroimidazo[1,2-a]pyrrolo[2,1-c]pyrazines, 1,3,4,6,7,11b-hexahydro-2H-pyrrolo[2??,1??:3,4]pyrazino[1,2-a]pyrimidines, and 2,3,4,5,6,7-hexahydro-1H-pyrrolo[2,1-c]-[1,4,7]triazacycloundecin-8(9H)-one.     

Some novel heterocyclic systems derived from 7-amino-2,3-dihydro-8-nitro-1H-pyrrolo[1,2-α]benzimidazole and the corresponding diamine

The preparation of 7-amino-2,3-dihydro-8-nitro-1H-pyrrolo[1,2-a]benzimidazole from 1,4-diacetamido-2,3-dinitrobenzene is described. Reaction of this compound with 2,5-dimethoxytetrahydrofuran produces 2,3-dihydro-8-nitro-7-N-pyrrolo-1H-pyrrolo[1,2-a]benzimidazole, which can be cyclised to produce two new heterocyclic ring systems, 9,10-dihydro-8H-pyrrolo[1,2-a]pyrrolo(1′,2′:1,2]imidazo[5,4-f]quinoxaline and 9,10-dihydro-8H-pyrrolo[2,1-c]pyrrolo[1′,2′:1,2]imidazo[4,5-h][1,2,4]benzotriazine. The corresponding diamine, 7,8-diamino-2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole undergoes a variety of condensation reactions to produce several new heterocyclic systems, for example, with formic acid, 1,7,8,9-tetrahydroimidazo-[4,5-e]pyrrolo[2,1-6]benzimidazole is formed and with diacetyl, 9,10-dihydro-2,3-dimethyl-8H-pyrrolo-[1′,2′:1,2]imidazo[5,4-y]quinoxaline is obtained.     

Synthesis of spiro[2H-indole-2,1′-1H-isoindole]-3,3′-diones,spiro[1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones and spiro[benzofuran-2,1′-isobenzofuran]-3,3′-diones via transannular reactions of eight membered ring intermediates

An auto oxidation-rearrangement product 4 was isolated from a high dilution reaction of ninhydrin with 3,4,5-trimethoxyaniline in water. A general synthesis of this compound and its derivatives 4–6 was devised by oxidation of tetrahydroindeno[1,2-b]indol-10-ones 1–3 with sodium periodate to give isoindolo[2,1-a]-indole-6,11-diones 4–6 in good yield. Compounds 4–6 can be easily transformed into spiro[1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones 8–10 , spiro[2H-indole-2,1′-1H-isoindole]-3,3′-diones 11–13 and isoindole[1,2-a:2′,1′-b]pyrimidine-5,15-diones 15, 16 in high yields. Analogous reactions were performed on 3-amino-5a, 10a-dihydroxybenzo[b]indeno[2,1-d]furan-10-one ( 17 ) to give a dibenzoxocintrione 18 , spiro-[benzofuran-2,1′-isobenzofuran]-3,3′-dione 19 and an isoindol-1-one 20 .     

Convenient synthesis of fused heterocycles from α-ketohydroximoyl chlorides and heterocyclic amines

Nitroso derivatives of imidazo[1,2-a]pyridine ( 11, 13, 14 ), imidazo[1,2-a]pyrimidine ( 15 ), imidazo[1,2-a]pyrazine ( 16 ), imidazo[1,2-b]pyrazole ( 17 ), and imidazo[1,2-b]-1,2,4-triazole ( 19 ) were obtained in good yields from α-ketohydroximoyl chlorides 3 and 2-aminopyridines ( 4–6 ), 2-aminopyrimidine ( 7 ), 2-aminopyrazine ( 8 ), 5-amino-3-phenylpyrazole ( 9 ), and 3-amino-2H-1,2,4-triazole ( 10 ), respectively. Under different conditions, the reaction of 3 with 3-amino-2H-1,2,4-triazole ( 10 ) and 2-aminopyrazine ( 8 ) afforded the noncyclized substitution products 18 and 22 , respectively. The structures of the products were assigned and confirmed on the basis of their elemental analyses, spectral data, and alternate synthesis wherever possible.     

4-Oxo-3,4-dihydroquinazolinyl- and Benzimidazolylacetonitriles in Annelation Reactions of a Haloquinoline Ring

The interaction of 4-oxo-3,4-dihydroquinazolinyl- and benzimidazolylacetonitriles with 2,6-dihalobenzaldehydes leads to 3-(2,6-dihalophenyl)-2-(4-oxo-3,4-dihydro-2-quinazolinyl)acrylonitriles and 2-(1H-benzo[d]imidazol-2-yl)-3-(2,6-dihalophenyl)acrylonitriles respectively. As a result of intramolecular cyclization of these nitriles 4-halo-12-oxo-12H-quino[2,1-b]quinazoline-6-carbonitriles and 4-halobenzo[4,5]imidazo[1,2-a]quinoline-6-carbonitriles respectively are formed.     

Synthesis,Reactions, and Antimicrobial Evaluation of Some Polycondensed Thienopyrimidine Derivatives

Some novel indeno[2,1-b]thiophenes, indeno[1′,2′:4,5]thieno[2,3-d][1,2,3]triazines, indeno[1′,2′:4,5]thieno[2,3-d]pyrimidines, indeno[1′,2′:4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]pyrimidines, and indeno[1′,2′:4,5]thieno[2,3-d][1,2,4]triazolo[4,3-a]pyrimidines 2–16 were prepared starting with 2-aminoindeno[2,1-b]thiophene-3-carboxylic acid amide ( 1 ). Furthermore, the antimicrobial evaluation of the prepared products showed that many of them revealed promising antimicrobial activity.     

Synthesis of nitrogen heterocycle-fused 1,2,4-benzothiadiazine-1,1-dioxide, quinazolinone, and pyrrolidinone derivatives with a guanidine joint via sequential aza-Wittig reaction/intramolecular NH-addition cyclization/nucleophilic substitution ring closure methodology, using functionalyzed carbodiimides as key intermediates

We achieved efficient synthesis of imidazo- and pyrimido[1,2-b]benzo-1,2,4-thiadiazine-1,1-dioxides by the tandem aza-Wittig reaction/intramolecular NH-nucleophilic addition/NH-nucleophilic substitution cyclization methodology, involving sulfonamide ester-containing carbodiimides as the key intermediates. Similarly, imidazo[2,1-b]quinazolinones, imidazo[1,2-a]pyrimidinediones, and imidazo[1,2-a]imidazolidinediones were also synthesized through the aza-Wittig reaction-tandem cyclization strategy. When homochiral (l)-alanine methyl ester was incorporated as a building block into the corresponding iminophosphorane starting materials, we obtained optically active imidazo[1,2-b]benzo-1,2,4-thiadiazine and imidazo[2,1-b]quinazolinone derivatives without any racemization through the one-pot tandem methodology.     

Diverse synthesis of pyrimido[1,2-a]benzimidazoles and imidazo[2,1-b]benzothiazoles via CuI-catalyzed decarboxylic multicomponent reactions of heterocyclic azoles,aldehydes and alkynecarboxylic acids

We have developed a straightforward approach to diverse synthesis of 2,3-, 2,4-disubstituted pyrimido [1,2-a]benzimidazoles, 2,4,10-trisubstituted 2,10-dihydropyrimido [1,2-a]benzimidazoles and 2,3-disubstituted imidazo [2,1-b]benzothiazoles via multicomponent reactions (MCRs) of heterocyclic azoles, aldehydes with easily storable and handling alkynecarboxylic acids. In the presence of a catalytic amount of CuI and K₂CO₃, the pyrimido [1,2-a]benzimidazole or imidazo [2,1-b]benzothiazole scaffold could be rapidly constructed through a 6-endo-dig or 5-exo-dig cyclization, respectively. The preliminary mechanistic study suggested that the formation of 2,3- disubstituted pyrimido [1,2-a]benzimidazoles, which completes the assembly of the scaffold and its C-3 position functionalization in one pot, undergoes a novel cascade process involving a decarboxylation, A [3] coupling, 6-endo-dig cyclization, nucleophilic addition and dehydration.     

Synthesis of Imidazo[1,2‐a]pyridines and Imidazo[2,1‐b]thiazoles Attached to a Cycloalkyl or Saturated Heterocycle Containing a Tertiary Hydroxy Substitution

A new method has been developed for the synthesis of imidazo[1,2‐a]pyridines, imidazo[2,1‐b]thiazoles, and benzo[d]imidazo[2,1‐b]thiazoles attached to a cycloalkyl or saturated heterocycle containing a tertiary hydroxy substitution. Readily available substituted 2‐aminopyridines, 2‐aminothiazoles, and 2‐aminobenzothiazoles were treated with bromohydroxycycloalkyl ethanones to afford the desired products in good yields.     

Polycyclic N-Heterocyclic Compounds,Part 77: Synthesis of [1]Benzothieno[3′,2′:2,3]oxepino[4,5-d]pyrimidines and Evaluation of Their Antiplatelet Aggregation Activity

Reaction of 3-(3-cyanopropoxy)[1]benzothiophene-2-carbonitrile with sodium hydride gave 5-amino-1,2-dihydro[1]benzothieno[3,2-d]furo[2,3-b]pyridine and 5-amino-2,3-dihydro[1]benzothieno[3,2-b]oxepin-4-carbonitrile. The latter compound served as a convenient scaffold for the synthesis of the new heterocycles [1]benzothieno[3′,2′:2,3]oxepino[4,5-d]pyrimidines and the parent 1,2,4,5-tetrahydro[1]benzothieno[2′,3′:6,7]oxepino[4,5-e]imidazo[1,2-c]pyrimidine heterocyclic system. The new compounds described in this report were evaluated as inhibitors of platelet aggregation in vitro.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Polycyclic systems: Synthesis of isoindolo[2,1-b]-pyrrolo[1,2-d][2,4]benzodiazocine and isoindolo-[1,2-d]pyrrolo[1,2-a] [1,5]benzodiazocine

The synthesis of isoindolo[2,1-b]pyrrolo[1,2-d][2,4]benzodiazocine 7 and isoindolo[1,2-d]pyrrolo[1,2-a]-[1,5]benzodiazocine 13 are described starting from 2-(2-methoxycarbonyl)benzylphthalimide 1a and ethyl α-bromohomophthalate 9 respectively.     

NBS mediated protocol for the synthesis of N-bridged fused heterocycles in water

A facile and environmental friendly protocol for the synthesis of N-bridged fused bicyclic compounds such as imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[2,1-b]thiazole, from commercially available starting materials has been developed. The reaction proceeds via NBS mediated in situ formation of α-brominated intermediate of corresponding aromatic ketones, 1,3-diketones, β-keto esters, followed by trapping with suitable nucleophiles to provide these versatile imidazole fused bicyclic heterocycles in good yields under metal-free conditions.     

Synthesis of two novel bicyelic systems,imidazo[1,5-D]-as-triazine and imidazo[1,2-d]-as-triazine

4-Imidazolecarboxyaldehyde was condensed with methyl dithiocarbazinate and with ethyl carbazate, the resulting hydrazones were subjected to thermolysis in diphenyl ether at 175–240, to give imidazo[1,5-d]-as-triazine-4(3H)thione and imidazo[1,5-d]-as-triazin-4(3H)one, respectively. A number of 2-, 5-, and 2,5-substituted 4-imidazolecarboxaldehydes were also carried through this scheme. The same sequence of reactions with 2-imidazolecarboxaldehyde gave the novel system imidazo[1,2-d]-αs-triazine-5-(6H)-thione. Upon treatment with sodium hydride and methyl iodide, imidazo[1,5-d]-as-triazine-4(3H)thione and imidazo[1,2-d]-as-triazine-5(6H)-thione gave 4-methylthioimidazo[1,5-d]-as-triazine and 5-methylthioimidazo[1,2-d]-as-triazine, respectively. Displacement of the thiomethyl group was achieved with a selection of amine reagents in both of the above cases.