4.4- diethyl-3,5-dioxo

The same compound is obtained when proceeding according to the following alternative procedure. A mixture of 39.4 parts by weight of 2,4-dioxo-3,3-diethyl-5-oxymethylene-piperidine and 27 parts by weight of dibutylamine are heated to 150°C in a closed vessel. The 2,4-dioxo-3,3-diethyl-5-dibutylamino-methylene-piperidine formed melts at 77°C after having been recrystallized in petroleum ether. 

To this acid was then added 1 g of 4-ethyl-2,3-dioxo-1-piperazinocarbonyl chloride (from the reaction of N-ethylethylenediamine and diethyl oxalate to give 2,3-dioxo-4-ethyl-piperazine which Is then reacted with phosgene) and the resulting mixture was reacted at 15°C to 20°C for 2 hours. After the reaction, a deposited triethylamine hydrochloride was separated by filtration, and the filtrate was incorporated with 0.4 g of n-butanol to deposit crystals. The deposited crystals were collected by filtration to obtain 1.25 g of white crystals of 6-[ D(—l-Ct-(4-ethyl-2,3-dioxo-1 -piperazinocarbonylaminolphenylacetamido] penicillanic acid. Into a solution of these crystals in 30 ml of tetrahydrofuran was dropped a solution of 0.38 g of a sodium salt of 2-ethyl-hexanoic acid in 10 ml of tetrahydrofuran, upon which white crystals were deposited. The deposited crystals were collected by filtration, sufficiently washed with tetrahydrofuran and then dried to obtain 1.25 g of sodium salt of 6-[D(—)-a-(4-ethyl-2,3-di-0X0-1-piperazinocarbonylaminolphenylacetamido] penicillanic acid, melting point 183°C to 185°C (decomposition), yield 90%. 

CN (5)-[ 1,4 -bipiperidine]-1 -carboxylic acid 4,11 -diethyl-3,4,12,14-tetrahydro-4-hydroxy-3,14-dioxo-1H-... 

The 2,3-dioxo-6-thioxo-2,3,5,6-tetrahydro-l/7-imidazo[l,2-A]pyrazole 393 and 5,6-dioxo-2,3-dihydro-l//-imidazo[l,2- ]-imidazole 395 were synthesized by condensation of the respective 5-amino-3-thioxo-2,3-dihydro-pyrazole 392 and 2-aminoimidazoline 394 compounds with either oxalyl dichloride or diethyl oxalate in moderate to poor yields (Equations 178 and 179) <1995JPR472, 2002EJM845>. These cyclizations can suffer from various side reactions such as expulsion of CO, polymerization, or formation of open-chain products. To solve these problems, reagents such as oxalic acid bis-imidoyl- and bis-hydrazoylchlorides 397 and 400 as well as 2,3-dichloroquinoxalines 403... 

The cyclization of diethyl N-(2,3-methylenedioxyphenyl)aminomethy-lenemalonate in boiling diphenyl ether or Dowtherm A afforded 1,3-dioxo-... 

Phosphonic acid, [(1,3-dihydro-l,3-dioxo-2H-isoindol-2-yl)methyl]-, diethyl ester, 65, 119... 

Diethyl dioxosuccinate Butanedioic acid, dioxo-, diethyl ester (9) (59743-08-7)... 

Butanedioic acid, dioxo-, diethyl ester, (59743-08-7), 66, 149 Butanedioic acid, tetrahydroxy-, disodium salt (866-17-1 ), 66, 149... 

DIETHYLPHOSPHONOMETHYL-2, 2-DIMETHYL-1.3-DI0XEN-4-0NE, 66, 194-196, 202 Diethyl phthalimidomethylphosphonate Phosphonic acid, (phthalimidomethyl)-, diethyl ester Phosphonic acid, [(1,3-dihydro-l, 3-dioxo-2H-isoindol-2-yl)-methyl]-, diethyl ester (33512-26-4), 65, 119 DIHYDR0JASM0NE, 65, 26... 

Dioxo-8a-methyl-l, 2,3,4,6,7,8,8a-octahydronaphthalene has been obtained through the reaction of 2-methyl-l,3-cyclohexane-dione with acetonedicarboxylic acid and formaldehyde,3 4-diethyl-amino-2-butanone methiodide,3 pyridine and 4-diethylamino-2-butanone,4 triethylamine and 4-diethylamino-2-butanone,5 and by cyclization of 2-methyl-2-(3-oxobutyl)-l,3-cyclohexanedione using either aluminum fer/-butoxide or piperidine phosphate as catalyst.6 7... 

Diethyl-l,2,4,5-tetroketo-4,5-dihydro-pyridazine-3,6-dicarboxylate or 4,5-Dihydro-4,5-dioxo-3,6-pyridaztne-dicar boxy lie acidic-dioxide diethytester,... 

Many other [c]-fused pyridazines have been prepared similarly. 6-Methylpyridazine-3,4-dicarbalde-hyde (415) with hydrazine gives 3-methylpyridazino[4,5-c]pyridazine (416) (73JHC1081). 5-Oxo- and 5,8-dioxo-substituted pyridazino[4,5-c]pyridazines are prepared from ethyl 3-formylpyridazine-4-carboxylates and diethyl pyridazine-3,4-dicarboxylates, respectively, with hydrazine. Pyridazine-3,4-dicarbonitrile (417) with hydrazine gives the diamino heterocycle (418) (67JHC393). 

Cyclocondensation of ethyl 2-(4-oxo-l,4-dihydroquinazol-2-yl)acetate (305) and diethyl ethoxymethylenemalonate at 180°C gave diethyl 1,6-dioxo-5,6-dihydro-l //-pyrido[l, 2-a]quinazoline-2,4-dicarboxylate (306). 

Diethyl-2,4-dioxo-3-fluoro-10-methyl-5-phenyl- ElOa, 447 (H - F)... 

The structure of the reaction product of 2-aminopyridine and diethyl malonate, described by Chichibabin as 2,4-dioxo-3,4-dihydro-2//-pyrido-[l,2-<7]pyrimidine,96 was first questioned by Snyder and Robison253 on the basis of the high melting point and poor solubility of the compound. They suggested the tautomeric 2-hydroxy-4-oxo-4H-pyrido[l,2-a]pyrimidine structure. The problem was solved by Katritzky and Waring273 who compared the UV spectrum of the product with that of fixed tautomers and found that the product may best be described as anhydro- 2-hydroxy-4-oxo-4/f-pyrido[l,2- ]pyrimidinium)hydroxide (63). Because of the chemical behavior of these compounds, however, the contribution of other mesomeric forms to the structure has also been considered.122 Thus, PPP-SCF quantum chemical calculations suggest that 1,4-dipolar cycloadditions to the C-3 and C-9a atoms are to be expected.352 This type of reaction does in fact occur (see Section III,C,10). Katritzky and Waring273 estimated the ratio of the mesomeric betaine (63 R = H) and the 2-hydroxy-4-oxo tautomers to be about 20 1. 

RN HEPTAMETHYL-1, ll-DIOXO-2,7-( EPOXYPENTAOECA( 1,11,13ITRIENIMINOINAP-HTHOi2,1-bIFURAN-9-YLIOXY1- H.N-DIETHYL-, 21-ACETATE - 2750-76-7... 

---