Pyrano[4,3-d]pyrimidinium salts 5. Synthesis of 7-aryl-1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium salts and their reactions with nucleophiles

7-Arylpyrano[4,3-d]pyrimidinium salts were synthesized starting from 1,3,6-trimethyluracil. In the reactions with N-nucleophiles, these salts were found to undergo recyclization of the pyrylium ring, whereas the addition of C- and O-nucleophiles occurs at free position 5 of the system.     

Pyrano[4,3-d]pyrimidinium salts 4. Transformations of 5,7-diaryl-1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium bromides under the action of phenylhydrazines and aromatic acid hydrazides

Reactions of 5,7-diaryl-1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium bromides with phenylhydrazines and aromatic acid hydrazides have been studied. The reaction of the salts indicated with phenylhydrazine at ∼20 °C results in the pyrylium ring opening, whereas elevated temperature leads to recyclization products, i.e., 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4(1H,3H)-diones. The reactions of the starting bromides with m-carboxyphenylhydrazine and aromatic acid hydrazides lead to 6-(R-amino)-1,3-dimethyl-2,4-dioxo-1H,3H-pyrido[4,3-d]-pyrimidinium salts.     

Some substituted 4-aminothionaphtheno [3, 2-d] pyrimidines

Boiling 2-methyl-4-oxo-3,4-dihydrothionaphtheno[3,2-d]-pyrimidine with phosphorus oxychloride gives 2-methyl-4-chlorothionaphtheno [3,2-d]pyrimidine (II), in which the chlorine atom is mobile. Nucleophilic substitution of the mobile chlorine atom in compound II gives the 4-ethoxy,4-(N-piperidino),4-(N⁴-methyl-N-piperazino), 4-[2-(diethylamino)ethylamino],4-3-(diethylamino)-2-hydroxypropylamino]substituted derivatives.     

New organic nitrates. II. Synthesis of 2H-pyrido[2,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazin-4(3H)-ones, 2H-thieno[2,3-e]-1,3-oxazin-4(3H)-ones and 2H-thieno[3,4-e]-1,3-oxazin-2,4(3H)-diones

The preparation and the physico-chemical characterization of 2H-pyrido[2,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazin-4(3H)-ones, 2H-thieno[2,3-e]-1,3-oxazin-4(3H)-ones and 2H-thieno[3,4-e]-1,3-oxazine-2,4(3H)-diones are reported.     

Microwave promoted improved regioselective synthesis of 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones by radical cyclisation

In this work, two new effective methodologies have been adopted for the preparation of 5-(2′-bromobenzyloxy)pyrimidine-2,4-diones 6(a–k). In the first methodology, 5-hydroxy uracils 4(a–f) were alkylated with 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b under phase transfer catalysis condition using lithium hydroxide/tetrabutyl ammonium bromide in N,N-dimethylformamide at 45 °C, and in the second method, the microwave irradiation (MWI) protocol has been exploited by mixing 5-hydroxy uracils 4(a–f) with 30 % excess of 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b. A catalytic amount of TBAB and potassium carbonate was added and irradiated in an open Erlenmeyer flask in a microwave oven for 3–12 min. The tributyltin hydride-mediated radical cyclisation of 6(a–k) was carried out under MWI to generate 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones 7(a–k) in 80–89 % yield, and the reaction time was shortened compared to the previously reported conventional radical cyclisation method.     

Chemistry of 1,2,3-thiadiazole. IV. Synthesis of [1]benzoxepino-[3,4-d][1,2,3]thiadiazole, [1]benzothiepino-[3,4-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d]oxazole and [1]benzoxepino[4,3-d]oxazole. Four novel heterocycles

Starting from the readily available 4-bromomethy-5-carbethoxy 1,2,3-thiadiazole (V), 5-bromomethy-4-carbethoxy-1,2,3-thiadiazole (IX) and ethyl 2-aryl-5-bromomethyloxazole-4-carboxylate (XIV), 4,10-dihydro-10-oxo[1]benzoxepino[3,4-d][1,2,3]thiadiazole (Ia), 4,10-dihydro-10-oxo[1]benzothiepino[3,4-d][1,2,3]thiadiazole (Ib), 4,10-dihydro-4-oxo[1]benzothiepino[4,3-d] [1,2,3]thiazole (II), 2-aryl-4,10-dihydro-4-oxo[1]benzoxepino[4,3-d]oxazoles (XIXa-XIXc) and 2-aryl-4,10-dihydro-4-oxo[1]benzothiepino[4,3-d]oxazoles (XIXd-XIXf) were prepared.     

Über 4-Ureidooctahydropyrano[4,3-d]pyrimidinone

Zusammenfassung 5,6-Dihydro-2H-pyran-3-aldehyde reagieren mit Harnstoff zu 4-ureidooctahydropyrano[4,3-d]pyrimidin-2-ones. Einwirkung von Säure führt das 4-Ureidooctahydropyrano[4,3-d]pyrimidin-2-on in das 4-(2-Hydroxyäthyl)-hexahydropyrimido[4,5-d]pyrimidin-2,7-dion über.

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Heterocycles, XVIII: 4-Ureido-octahydropyrano[4,3-d]-pyrimidinones

5,6-Dihydro-2H-pyran-3-aldehydes react with urea to give 4-ureidooctahydropyrano[4,3-d]pyrimidin-2-ones. 4-Ureidooctahydropyrano[4,3-d]pyrimidin-2-one is cleaved by HCl to 4-(2-hydroxyethyl)-hexahydropyrimido[4,5-d]pyrimidin-2,7-dione.

     

Heterocyclic system. XI. Synthesis of 1H,4H-pyrazolo[4,3-b]pyrrolizine and 2H,4H-pyrazolo[4,3-b]pyrrolizine derivatives

Cyclization of pyrrolidinocarboxamide derivatives of 1-phenyl-5-(1H-pyrrol-1-yl)-1H-pyrazole-4-carboxylic acid and 2-phenyl-3-(1H-pyrrol-1-yl)-1H-pyrazole-4-carboxylic acid afforded imminium salts which were transformed into the corresponding ketones. Further reduction of the latter compounds furnished the title derivatives.     

Selenium heterocycles. XXXIX. Synthesis of thieno[3, 4-d]thiazole,thieno[3, 4-d]selenazole,selenolo[3, 4-d]thiazole and selenolo[3, 4-d]selenazole

Starting from readily available methyl 2-substituted4-methyl-5-thiazolyl ketone and methyl 4-methyl-2-phenyl-5-selenazolyl ketone, thieno[3, 4-d]thiazole, thieno[3, 4-d]selenazole, selenolo[3, 4-d]thiazole and selenolo[3, 4-d]selenazole were prepared. The structures of all compounds were confirmed by analytical and spectroscopic methods.     

Pyrano[4,3-d]pyrimidinium salts 3. Reactions of 1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium salts with azomethines

Reactions of 1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium salts with azomethines have been studied. The reactions lead to 1,3-dimethyl-2,4-dioxo-1H,3H-pyrido-[4,3-d]pyrimidinium salts and aromatic aldehydes.     

A synthetic entry to isoxazolo[5,4-d]pyrimidine-4(5H)thione and isothiazolo[4,3-d]isoxazole

4-Thiocarbamoyl-5-aminoisoxazole 4 was used as a convenient starting material for preparing both isoxazolo[5,4-d]pyrimidine-4(5H)thiones 5 and 4-aminoisothiazolo[4,3-d]isoxazole 6 . The structure of the latter compound was definitively assigned by X-ray analysis.