Reaction of 4,5-diamino-3-methyl-1-phenylpyrazole with 3-dimethylaminopropiophenones. Synthesis of new 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines

New 4-Aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines were obtained from the reaction of 4,5-diamino-3-methyl-1-phenylpyrazole 1 with one equivalent of the 3-dimethylaminopropiophenones 2 in absolute ethanol. The structures of 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines 3 and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines 4 were determined by detailed nmr measurements.     

Synthesis of 6,7,8,9-tetrahydro-5H-pyrimido-[4,5-b][1,4]diazepine-6,8-diones

The sodium ethoxide catalyzed condensation of 4,5-diaminopyrimidine ( 3 ) with diethyl malonate afforded 6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 4 ). Methylation of 6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 4 ) using sodium hydride and two equivalents of iodomethane gave 5,9-dimethyl-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 5 ) which on further methylation using sodium hydride and one equivalent iodomethane yielded 6,7,8,9-tetrahydro-5,7,9-trimethyl-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 6 ). Reaction of 6,7,8,9-tetrahydro-5H-pyrirnido[4,5-b][1,4]diazepine-6,8-dione ( 4 ) with 4.2 equivalents of sodium hydride and 4.1 equivalents of iodomethane afforded 6,7,8,9-tetrahydro-5,7,7, 9-tetramethyl-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 7 ). 6,7,8,9-Tetrahydro-5,7,7,9-tetramethyl-5H-pyrimido[4,5-b][1,4]diazepine-6,8-dione ( 7 ) exhibited weak anticonvulsant activities in the subcutaneous pentylenetetrazole and maximal electroshock anticonvulsant screens indicating it is a partial bioisostere of the anticonvulsant drug clobazam ( 2 ).     

New heterocyclic structures. [1,3]Thiazino[3,2-a]purine and [1,2,3]triazolo[4,5-d][1,3]thiazino[3,2-a]pyrimidine

Derivatives of two new molecular structures, namely, [1,3]thiazino[3,2-a]purine and [1,2,3]triazolo[4,5-d]-[1,3]thiazino[3,2-a]pyrimidine, were synthesized together with other heterocyclic compounds. Retrosynthetic analysis of their molecular skeletons suggested a simple way of obtaining 3,4-dihydro-7,8-diamino-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one, which is a useful intermediate for their synthesis. This intermediate and the thiazole homologue were obtained directly by reaction of 5,6-diamino-2,3-dihydro-2-thioxo-4(lH)-pyrimidi-none with 1,3- or 1,2-dibromoalkane, respectively.     

Reaction of 4,5,6‐triaminopyrimidine and 2,4,5,6‐tetraaminopyrimidine with 3‐dimethylaminopropiophenones. Synthesis of new 4‐aryl‐2,3‐dihydropyrimido[4,5‐b][1,4]diazepines

Several new 6‐amino‐ and 6,8‐diamino‐4‐aryl‐2,3‐dihydropyrimido[4,5‐b][1,4]diazepines were obtained from the reaction of 4,5,6‐triaminopyrimidine 1a and 2,4,5,6‐tetraaminopyrimidine 1b with one equivalent of 3‐dimethylaminopropiophenones 2 in absolute ethanol. Structure analysis of 6‐amino‐ and 6,8‐diamino‐4‐aryl‐2,3‐dihydropyrimido[4,5‐b][1,4]diazepines 3a‐i , determined by detailed nmr measurements, reveals a high regioselectivity of this reaction.     

Synthesis of 2,3-dihydropyrido- and 2,3-dihydropyrimido-[1,4]diazepines from triaminopyridine and triaminopyrimidine

The reaction of 2,3,6-triaminopyridine 1 and 4,5,6-triaminopyrimidine 2 with one equivalent of the chal-cones 3, in acetic acid, leads to the formation of the 8-amino-2,3-dihydro-1H-pyrido[2,3-b][1,4]diazepine and 6-amino-2,3-dihydro-1H-pyrimido[4,5-b][1,4]diazepine derivatives 4 and 5 . The products were characterized by NMR techniques such as ¹³C, ¹H, and DEPT including selective ¹³C{¹H} decoupling experiments.     

Synthesis of 4-aryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]-diazepin-6-ones from 4,5-diamino-1H-pyrimidin-6-ones and 1-aryl-3-(dimethylamino)-1-propanones

The reaction of 1-aryl-3-(dimethylamino)-1-propanones 1 with one equivalent of 4,5-diamino-1H-pyrimidin-6-ones 2 , in acidic medium, leads to the formation of 4-aryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b]-[1,4]diazepin-6-ones 3 . The structure elucidation of the products is based on detail nmr analysis of experiments such as ¹³C, ¹H and DEPT including selective ¹³C{¹H} decoupling experiments.     

New heterocyclic structures. [1,2,5]Thiadiazolo[3′,4′:4,5]pyrimido-[2,1-b][1,3]thiazine and thiazolo[3,2a][1,2,5]thiadiazolo[3,4-d]pyrimidine

Derivatives of two new molecular structures, namely, 7,8-dihydro-6H,10H-[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-10-one and 6,7-dihydro-9H-thiazolo[3,2-a][1,2,5]thiadiazolo[3,4-d][pyrimidin-9-one, and derivatives of N-substituted sulfamic acid, namely, (8-amino-3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-on-7-yl)sulfamic acid and (7-amino-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-on-6-yl)sulfamic acid, were separated out as by-products in the reduction reaction of 8-amino-3,4-dihydro-7-nitroso-2H,6H-pyrimido[2,1- b][1,3]thiazin-6-one and 7-amino-2,3-dihydro-6-nitroso-5H-thiazolo[3,2-a]pyrimidin-5-one derivatives, respectively, with sodium hydrosulfite. A mechanism of reaction, which hypothesizes the action of sodium hydrosulfite in an asymmetic form, is proposed. The results of single-crystal X-ray investigation on 7,8-dihydro-6H,10H-[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-10-one (R = 0.032 for 863 reflections) and (8-amino-3,4-dihydro-2H,6H-pyrimido[2,1-b]- [1,3]thiazin-6-on-7-yl)sulfamic acid, sodium salt (R = 0.028 for 3507 reflections) are reported.     

Reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones with two equivalents of chalcones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with two equivalents of the chalcones 2 leads in an acidic medium to the formation of the 2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-one derivatives 3a-d . The structure elucidation of the products is based on nmr measurements and an X-ray diffraction.     

Coupling to the pyrimido[4,5-b][1,4]oxazine ring system: Synthesis of potential antifolates

The ability of 2-amino-4-hydroxy-7H-pyrimido[4,5-b][1,4]oxazine derivatives to inhibit dihydrofolate reductase led to a search for means of synthesizing new side chain substituted analogs of this marginally stable pyrimidooxazine system. A study of the synthesis and use of 6-functionalized pyrimido[4,5-b][1,4]oxazines for coupling side chains was begun and has now revealed methods for coupling p-aminobenzoic acid with 2-amino-4-hydroxy-6-carboxy-7H-pyrimido[4,5-b][1,4]oxazine and hydrolyzed 2-amino-4-hydroxy-6-carbe-thoxymethylene-6,7-dihdyro-5H-pyrimido[4,5-b][1,4]oxazine. The products are of interest for evaluation as potential antifolates.     

Heterocyclizations of Functionalized Heterocumulenes with C,N- and C,O-Dinucleophiles: II.* Reaction of 1-Chloro- and 1,1-Dichloroalkyl Isocyanates and 1-Chloroalkylidenecarbamates with 2-Bensothiazolylacetonitrile, 2-Benzothiazolylacetates,and Bis(2-benzothiazolyl)methane

1-Chloroalkyl isocyanates react with 2-R-methylbenzothiazoles [R = CN, C(O)OAlk, 2-benzothiazolyl] in the presence of triethylamine to give 4-R-2,3-dihydro-1H-pyrimido[6,1-b][1,3]benzothiazol-1-ones. The same reaction at elevated temperature in the absence of a base yields isomeric 4-R-2,3-dihydro-1H-pyrimido[6,1-b][1,3]benzothiazol-3-ones. 4-R-1H-Pyrimido[6,1-b][1,3]benzothiazol-1-ones are formed in the reaction of 1,1-dichloroalkyl isocyanates or methyl 1-chloroalkylidenecarbamates with 2-benzothiazolylacetonitrile or bis(2-benzothiazolyl)methane.     

Synthesis of Benzofuro[3,2-e][1,4]diazepines

A synthesis of 4-N-oxides and of 3-hydroxy derivatives of 1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-ones and of 2,3-dihydro-1H-benzofuro[3,2-e][1,4]diazepines is described. Condensation of 2-acetyl- and 2-benzoyl-3-ethoxycarbonylaminobenzofurans with acrylonitrile gave derivatives of 1,2-dihydro- and of 1,2,3,4-tetrahydrobenzofuro[3,2-b]pyridine.     

The reaction of aromatic α,β-unsaturated ketones with 4,5-diamino-1,6-dihydropyrimidin-6-ones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m . The structure elucidation of the products is based on detailed nmr investigations including selective ¹³C[¹H] decoupling experiments.     

Reaction of 4,5-diaminopyrimidine and ethyl acetoacetate: Synthesis and chemistry of isomeric dihydropyrimido[4,5-b][1,4] diazepinones

Depending upon reaction conditions, 4,5-diaminopyrimidine and acetoacetic ester gave a variety of condensation products, including the two isomeric dihydropyrimido[4,5-b][1,4]-diazepinones. Under conditions leading to bicyclic products, the formation of 1,5-dihydro-4-methyl-2H-pyrimido[4,5-b][1,4]diazepin-2-one ( 2 ) was strongly favored. The isomeric 3,5-dihydro-2-methyl-4H-4-one compound ( 4 ) was best obtained by cyclization of ethyl 3-(4-amino-5-pyrimidylamino)crotonate ( 3 ) under base catalysis. Thermal rearrangement of 2 and 4 proceeded, in each instance, with loss of the isopropenyl moiety and gave 8-purinone. Compound 4 underwent ring contraction under the influence of alkoxide to yield a product which was shown to be the 7-isopropenyl-8-purinone ( 6 ).     

Cyclization reactions of 1,3-dibromopropan-2-ol, 2,3-dibromopropan-1-ol and 1-bromomethyloxirane with 6-amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone

The cyclization reactions, carried out in strongly- or weakly-basic media, are described. Sometimes, 7-amino-2,3-dihydro-3-hydroxymethyl-5H-thiazolo[3,2-a]pyrimidin-5-one is separated out, together with 8-amino-3,4-dihydro-3-hydroxy-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one, as the principal product. A mechanism of reaction, during which the cyclizating agents are changed into oxirane derivatives, is proposed. The results of single-crystal X-ray investigations on 8-amino-3,4-dihydro-3-hydroxy-7-nitroso-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one (R = 0.035 for 1013 reflections), and on 7-hydroxymethyl-6,7-dihydrothiazolo[3,2-a][1,2,3]triazolo[4,5-d]pyrimidin-9(1H)-one (R = 0.027 for 1607 reflections) are reported.     

Cycloaddition reactions of 2,3-dihydro-1H-1,4-diazepines with nitrile oxides and imines. Synthesis of bis[1,2,4]oxadiazolo-and bis[1,2,4]triazolo[1,4]diazepine derivatives

New heterotricyclic systems, 6,10a,11,11a-tetrahydro-5H-bis[1,2,4]oxadiazolo[4,5-d:5′,4′-g][1,4]diazepines 6,7,9-11 and 5,6,10,10a,11,11a-hexahydro-1H-bis[1,2,4]triazolo[4,3-d:3′,4′-g][1,4]diazepines 8,12 have been obtained by double site- and regie-specific 1,3-dipolar cycloaddition of mesitylnitrile oxide ( 1 ) or diphenylnitrile imine ( 2 ) to 5,7-disubstituted 2,3-dihydro-1H-1,4-diazepines 3-5. The structure of the synthesized bis-adducts 6-12 shows that the hetero double bonds are much more reactive than the olefinic ones in the dipolarophiles under study. No evidence for the formation of mono-adducts was obtained.     

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.     

4-(3-Cyanopyridin-2-ylthio)acetoacetates in synthesis of heterocycles

Substituted 2-amino-4-aryl-3-cyano-5-oxo-5,6-dihydro-4H-pyrano[2,3-d]pyrido[3",2":4,5]thieno[3,2-b]pyridines were synthesized by the reactions of 4-hydroxy-1H-thieno[2,3-b;4,5-b]dipyridin-2-ones with arylidenemalononitriles or by the three-component reactions of hydroxythienodipyridinones with aldehydes and malononitrile in DMF in the presence of triethylamine. Methods for syntheses of substituted 3-alkoxycarbonyl-6-amino-4-aryl-2-(3-cyanopyridin-2-ylthiomethyl)-4H-pyrans were developed on the basis of the reactions of 4-(3-cyanopyridin-2-ylthio)acetoacetates and arylidenemalononitriles or aldehydes and malononitrile. Ethyl 4-(3-cyanopyridin-2-ylthio)acetoacetate and 4-methoxybenzylidenecyanothioacetamide were used for the synthesis of 6-(pyridin-2-ylthiomethyl)-3-cyanopyridine-2(1H)-thione.     

The Mannich reaction in the synthesis of N,S-containing heterocycles

Reactions of 6-aryl-5-cyano-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidines with formaldehyde and primary amines gave earlier unknown 3,4-dihydro-2H,6H-pyrimido[2,1-b]-[1,3,5]thiadiazine derivatives in 58–94% yields. In boiling AcOH, these pyrimidothiadiazines underwent the retro-Mannich reaction leading to the starting pyrimidine-2-thiones. The structure of 3-(4-ethoxyphenyl)-6-oxo-8-phenyl-3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3,5]thiadiazine-7-carbonitrile was studied by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1384–1387, July, 2007.     

Synthesis of 5,6-dihydro-4H-pyrrolo[1,2-a]thieno[2,3-f][1,4]diazepines

The reduction of 1-[3-(thienyl-2-carbonitrile)]pyrrole, formed by condensation of 3-aminothiophene-2-carbonitrile with 2,5-dimethoxytetrahydrofuran, gave 1-[3-(thienyl-2-aminomethyl)]pyrrole. This compound was found to be a convenient intermediate for the preparation of 4-aryl-5,6-dihydro-4H-pyrrolo[1,2-a]thieno-[2,3-f][1,4]diazepines which was accomplished by two different synthetic routes.     

Deep eutectic solvent-mediated expedient multicomponent synthesis of oxazine scaffolds

A simple, efficient, and eco-friendly protocol for the synthesis of 1,3-oxazine derivatives, viz. 7-aryl-7,8-dihydro-6H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-e][1,3]oxazines and 3-aryl-3,4-dihydro-2H- naphtho[2,3-e][1,3]oxazine-5,10-diones, involving one-pot multicomponent condensation reaction of various amines and formaldehyde with sesamol/2-hydroxy-1,4-naphthoquinone, respectively, catalyzed by a choline chloride–oxalic acid deep eutectic solvent has been developed. The method offers several advantages, including mild reaction conditions, simple operating procedure, recyclable and biodegradable catalyst, short reaction times, and excellent yields of the target products.