2- 5,5-dimethyl-1,3-dioxo

Acetoy-2,4-dimethyl-3,5-dioxo-E16c, 802 (2,3,4,5-H4 — 1,2,4-triazin/Enol-ester)... 

Fig. 12. Structure of trimeric dimethyl(dioxo)(pyridme)osmium(VI), 0s306(py)3(Me)6. From Ref. U81).

Using an oxalic ester replaces a reactive hydrogen atom by an oxo ester (alkoxalyl) group.750 Thus diethyl 3-methyl-2-oxoglutarate is obtained in 70% yield from ethyl propionate and diethyl oxalate 751 and dimethyl dioxo-homonorcamphorate [methyl(3-methoxycarbonyl-2-oxocyclopentyl)glyoxalate] can be prepared in 90% yield from ethyl 2-oxocyclopentanecarboxylate and methyl oxalate 752... 

Of the three benzenetricarboxyhc acids, only trimellitic acid as the anhydride is commercially produced in large volume, by Hquid-phase air oxidation of either pseudocumene or dimethyl benzaldehyde. The pseudocumene oxidation is another variant of the cobalt—manganese—bromine catalyst in acetic acid solvent as described in the terephthaUc acid section. The acid is available as a laboratory chemical (99). The lUPAC name of trimellitic anhydride is 5-isobenzofurancarboxyhc acid (l,3-dihydro-l,3-dioxo). 

Indolizidine, 5,7-dimethyl-conformations, 4, 451 Indolizidine, 3,5-dioxo-IR spectra, 4, 450 reactivity, 4, 462... 

Purine, 1,6-dihydro-8,9-dimethyl-6-thioxo-synthesis, 5, 583 Purine, 2,6-dimethoxy-synthesis, 5, 596 Purine, 2,6-dimethoxy-7-methyl-rearrangement, 5, 558 Purine, 2,7-dimethyl-halogenation, 5, 547 Purine, 7,9-dimethyl-UV spectra, 5, 517 Purine, 8,8-dimethyl-synthesis, 5, 580 Purine, 6-dimethylamino-mass spectra, 5, 519 occurrence, 5, 600 Purine, 6-dimethylamino-9-benzyl-alkylation, 5, 531 Purine, 3,7-dimethyl-6,8-dioxo-methylation, 5, 534 Purine, 6,8-dioxo-alkylation, 5, 534... 

Pyridazino[4,3-c]pyridazine, 2,6-dimethyl-3,4-dioxo-2,3,4,6,7,8-hexahydro-4-( p-bromophenylhydrazone) synthesis, 3, 352... 

Trihydroxypteridine exists predominantly in the dioxo-mono-hydroxy form 191(R = H), its ultraviolet spectrum closely resembling those of both the 1- and the 3-methyl derivatives and that of l,3-dimethyl-7-methoxypteridine-2,4-dione (191, R = Me). These spectra are quite different from those of 8-methyl- (192, R = H) and l,3,8-trimethyl-pteridine-2,4,7-trione (192, R = Me), which are similar to each other and to those of other 8-substituted pteridine-2,4,7-triones. However, the ultraviolet spectrum of 2,4,7-trihydroxypteri-dine does, indeed, show that a small proportion of the trioxo form is present at equilibrium. A somewhat larger proportion of the 6-methyl derivative exists in the trioxo form, although structure 193 predominates. The trioxo form (194) of 2,4,7 trihydroxy-l,3,6-trimethyl-pteridine is the most important tautomer, but the corresponding 6-carboxylic acid exists entirely in the monohydroxy-dioxo form 195. 

Caffeine (128) and dimethyl sulfate in nitrobenzene give the fully methylated dioxo compound 129. In the same way that 2,4-dialk-oxypyrimidines give unstable quaternary salts which decompose to the N-alkyl oxo compounds even at room temperature, the action of... 

The 3-amino-8-oxo derivative of 1,2,4,5,7-pentaazanaphthalene (475) is known as well as various 3-substituted derivatives of the 6,8-dioxo compound. The 3-methylthio- and 3-ethylthio-6,8-dioxo derivatives and their 7-methyl and 5,7-dimethyl analogs were prepared by ring-closure. 3-Ethylthiopyrimido[4,5-e]-as-triazine-6,8-dione was 3-substituted with alkali 2N, 100°, > 30 min) or acid 2N, 100°, < 2 hr, 70% yield) and with ammonia, aniline, piperidine, or monoalkylamines (in pyridine, 115°, 4 hr, 75-85% yield). ... 

Dipolar eycloaddition reaction of thioisomiinchnones 208 with dimethyl aeetylenediearboxylate (DMAD) furnished adduets 209, whieh underwent a sulfur extrusion to give 2-substituted-7-phenyl-l,8-dioxo-l//,8//-pyrido[l,2-c]pyrimidine-5,6-dicarboxylates 210 (OOOL581). 

Chemical Name N-[(cyclohexylamino)carbonyl] -4-[2-(3,4-dihydro-7-methoxy-4,4-dimethyl-1,3-dioxo-2(1 H)-isoquinolinyl)ethyl] benzenesulfonamide... 

R = CH, methyl 3- 2,2-dimethyl-3,3-dioxo-i,3-oxathiun-4-yl)butanoate yield 62%... 

Dioxo-l,3-dimethyl-tetrahydro-imidazol- (4-spiro-2) - 4,6,7-trimethyl-1,2,3.4-tetrahydro-chinoxalin ... 

Dioxo-2,3-dimethyl-1,2,3,4-tetrahydro-phthalazin wird in Acetat-Puffer im we-sentlichen zuml-Oxo-2,3-dimethyl-l,2,3,4-tetrahydro-phthalazin (80% d.Th.) reduziert, in 4n Salzsaure wird dagegen unter Methylamin-Abspaltung 1 -Oxo-2-methyl-2,3-dihy-dro-isoindol (46% d.Th.) erhalten1 (vgl. a. S. 595f.) ... 

Nur eine Carbonyl-Gruppe wird bei der Hydrodimerisierung von 1,3-Dioxo- 1,3-diphenyl-propan an Quecksilber reduziert [90% d.Th. 1,6-Dioxo-l,6-diphenyl-hexandiol-(3,4)]9-, analog verhalt sich 3,5-Dioxo-l,l-dimethyl-cyclohexan (Dimedon)10 ... 

Dimethyl-7 -hydroxymethyl-8/i-carboxyme-thyl-4/i-mcthoxycarbonyl-aus 4a,9-Dimethyl-8/i-carboxymethyl-4/i,7 -dimethoxycarbonyl-dekalin und Natriumtrime-thoxy-hydrido-borat 201 Dioxo- 732 9-Hydroperoxy- 570 Hydroxy- 605, 732, 747 9-Hydroxy- 570... 

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