Synthesis of novel 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6]-[1,3,5]triazino[1,2-a]benzimidazoles

Reaction of 4-amino-2-methylbenzimidazo[1,2-a][1,3,5]triazines 2 with diethyl ethoxymethylenemalonate afforded 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6][1,3,5]triazino[1,2-a]benzimidazoles 3 , a new ring system.     

Synthesis of a new scaffold: the 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione nucleus

This paper describes a modified method of preparation of a number of alpha-aryl-alpha-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding alpha-aryl-alpha-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective alpha-aryl-alpha-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, (1)H- and (13)C- NMR analysesand by elemental C, H and N analysis.     

2,3,5,8(1)-Tetrahydroimidazo[1,2-a]pyrimidine-2,5-dione derivatives

The corresponding ylidene, azomethine, and azo derivatives of 2,3,5,8(1)-tetrahydroimidazo [1,2-a]pyrimidine-2,5-dione were synthesized by reaction of 7-methyl-and 6-bromo-7-methyl-2,3,5,8(1)-tetrahydroimidazo[1,2-a]pyrimidine-2,5-diones with aldehydes, insatin, aromatic nitroso compounds, and arenediazonium salts. Ylidene derivatives of 7-methyl-2,3,5,8(1)-tetrahydroimidazo[1,2-a]pyrimidine-2,5-dione were also obtained by reaction of 2-amino-4-methyl-6-oxo-1,6-dihydro-1-pyrimidylacetic acid with carbonyl compounds.     

Synthesis of 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro[isobenzofuran-1,4′-thiopyrans] and 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro-[isobenzofuran-1,4′-pyrans]

The 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro[isobenzofuran-1,4′-thiopyran] ring system ( 2a ) has been prepared from o-bromobenzoic acid. The 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro[isobenzofuran-1,4′-pyran] ring system ( 3a ) has been prepared from 2-bromobenzhydrol methyl ether. Several 3-(dimethylaminoalkyl) derivatives of both 2a and 3a were prepared by lithiation followed by alkylation.     

Synthesis and Biological Activity of Tetrahydropyrido[2′,3′:4,5]imidazo[1,2-c]pyrimidine-6,8-diones

Substituted 4-oxoquinoline-3- ( 1a ) and 4-oxo-1,8-naphthyridine-3- ( 1b ) carboxylic acids are clinically useful antibacterial agents exerting their activity by inhibiting the subunit A of DNA gyrase. Recently, pyrimido-[1,6-a]benzimidazoles 2 were found to be a new class of inhibitors of this enzyme. As, in 1 , replacement of C(8) by the N-atom was shown beneficial for the biological properties, a synthesis of the corresponding aza analogues of 2 has been carried out. The synthesis, DNA gyrase inhibitory activity, and in vitro antibacterial activity of the target compounds 16–19 are reported.     

Improved microwave-assisted catalyst-free synthesis of 9-aryl-5,9-dihydropyrimido[4,5-d][1,2,4]triazolo[1,5-a]pyrimidine-6,8(4H,7H)-dione derivatives

A green regioselective synthesis of some new and known 9-aryl-5,9-dihydropyrimido[4,5-d][1,2,4]triazolo[1,5-a]pyrimidine-6,8(4H,7H)-diones has been described via the microwave-assisted one-pot reaction of 3-amino-1H-1,2,4-triazoles, aromatic aldehydes and barbituric acids under solvent- and catalyst-free conditions. This operationally simple procedure is less laborious and provides a better scope than previously reported procedures.     

Synthesis of N,N-dimethyl(diethyl)-7-aryl-5-methyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxamides

Russian Journal of Organic Chemistry -     

Synthesis of imidazo[1,2-a]pyridine-6-carbohydrazides and 1H-pyrido[1,2-a]pyrimidine-7-carbohydrazides

The one-pot, multicomponent synthesis of imidazopyridine and pyridopyrimidine fused heterocyclic systems from readily available diamines, l,l-bis(methylthio)-2-nitroethene, cyanoacetohydrazide and aromatic aldehydes in good to high yields is described. This protocol has the advantages of simple work-up, mild reaction conditions, absence of catalyst and provides an entry point to fused heterocyclic structures.     

The stereochemistry of 1,6,7,12b-Tetrahydro-2H,4H-[1,2] oxazino[3′,4′:1,2]-pyrido[3,4-b]indole and of 1,2,3,6,7,12b-Hexahydro-3-methyl-4H-pyrimido[3′,4′:1,2]pyrido[3,4-6] indole

From an analysis of nmr spectral data, 1,6,7,12b-tetrahydro-2H,4H-[1,3 ]oxazino[3′, 4′ :1,2]-pyrido[ 3,4-b ]indole is shown to exist in solution at room temperature almost entirely in the cis-fused ring conformation with the nitrogen lone pair bisecting the C4 methylene group whereas under the same conditions 1,2,3,6,7,12b-hexahydro-3-methyl-4H-pyrimido[3′,4′:1,2] pyrido-[3,4-b ]indole exists as an approximately 50:50 equilibrium mixture of the cis and trans-fused ring conformations.     

Lanthanide metallocene complexes of the 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato Ligand, (hpp)1-

Reaction of the lanthanide metallocene allyl complexes, (C(5)Me(5))(2)Ln(eta(3)-CH(2)CHCH(2))(THF) (Ln = Ce, Sm, Y) with 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp, forms a series of metallocene complexes, (C(5)Me(5))(2)Ln(hpp) (Ln = Ce, Sm, Y) in which the (hpp)(1-) anion coordinates as a terminal bidentate ligand. Isomorphous structures were observed by X-ray crystallography regardless of the size of the metal. The acetonitrile adduct, (C(5)Me(5))(2)Sm(hpp)(MeCN), was also crystallographically characterized to provide an unusual pair of eight- and nine-coordinate complexes. The coordination mode of the (hpp)(1-) anion in these complexes is compared with that in other heteroallylic metallocenes like the caprolactamate (C(5)Me(5))(2)Y(ONC(6)H(10)) and the dithiocarbamate (C(5)Me(5))(2)Sm(S(2)CNEt(2)), which was also structurally characterized.     

Conversion of 4-amino-1H-1,5-benzodiazepine-3-carbonitrile to pyrazolo[3,4-d]pyrimidines,pyrimido[1,6-a]benzimidazole,and pyrazolo[3′,4′:4,5]pyrimido[1,6-a]benzimidazoles

The reactions of multifunctional compounds 2a, b, c, 3a, b and 4a, b which were readily obtained from 4-amino-1H-1,5-benzodiazepine-3-carbonitrile 1 with orthoesters are described, and derivatives of pyrazolo-[3,4-d]pyrimidines 5 , pyrimido[1,6-a]benzimidazole 9 , and pyrazolo[3′,4′:4,5]pyrimido[1,6-a]benzimidazole 10 are synthesized.     

Synthesis of diimidazo[1,2-a:2′,1′-c]pyrazines and diimidazo[1,2-a:2′,1′-c] [1,4]diazepines

Two new heterocyclic compounds, diimidazo[1,2-a:2′,1-c]pyrazine and 5H-diimidazo[1,2-a: 2,1′-c][1,4]diazepine have been synthesized by various routes from 2,2′-biimidazole (1) (2) together with some hydro, hydroxy and alkyl derivatives.     

Syntyhesis of 1,2,4,5-Tetrazino[1,6-a: 4,3-a′]diquinoxaline

A new one-step synthesis of 2 (1H)-quinoxalinone oxime ( 3 ) from (1,2-benzenediamine ( 1 ) and s-trans-chloroethanedial dioxime ( 2 ) is described. This oxime is converted into a new heterocyclic compound, 1,2,4,5,-tetrazino)[1,6-a: 4,3-a′]diquinoxaline ( 4 ), by the template effect of Co(II) and Ni(II) ions.     

Synthesis and reduction of thieno[2′,3′(3′,2′ or 3′,4′):5,6]-azocino[2,1-a]isoindole-7, 13-diones

A synthesis of the thieno[2′,3′(3′,2′ or 3′,4′):5,6]azocino[2,1-a]isoindole-7,13-diones 6a-c was developed from N-thienylethylphthalimides 3a-c using a Wittig reaction followed by a Friedel-Crafts cyclization of acetic acid derivatives 5a-c . Reduction of ketones 6a-c into alcohols 7a-c was stereo specific.     

A polarographic study of the iron-2-hydroxymethyl-6-(2′-hydroxymethyl-5′-hydroxy-4′-pyrone-6′)-pyranyl-3,2[b]pyran-4,8-dione complex

A polarographic study has been carried out on the colored product formed in the interaction of iron(III) with 2-hydroxymethyl-6-(2′-hydroxymethyl-5′-hydroxy-4′-pyrone-6′)-pyranyl-3,2[b]pyran-4,8-dione. Measurements using the differential pulse method show that iron(III) exhibits a coordination number of 2 and a reproducible formation constant that varies somewhat depending upon the supporting electrolyte employed.     

Synthesis of Methyl 6-Acyl-7-aryl-4,7-dihydrotetrazolo-[1,5-a]pyrimidine-5-carboxylates

Russian Journal of Organic Chemistry -