Uracil 1,3-dimethyl-, oxidation

Uracil, 6-dimethoxymethyl-3-methyl-2-thio-synthesis, 3, 113 Uracil, 1,3-dimethyl-dimers, 3, 74 Uracil, 3,6-dimethyl-synthesis, 3, 106, 110 Uracil, 5-fluoro-as anticancer drug, I, 263 antineoplastic activity, 3, 152 as pharmaceutical, I, 159 reactions, 2, 59 synthesis, 3, 70 Uracil, 6-fluoro-hydrolysis, 3, 101 Uracil, 5-hydroxy-1,3-dimethyl-synthesis, 3, 133 Uracil, hydroxymethyl-oxidation, 3, 91... 

Electron-rich 6-[(dimethyl(amino)methylene)amino uracil 82 underwent [4+2] cycloaddition reactions with various in situ generated glyoxylate imine and imine oxides to afford novel pyrinhdo[4,5-J]pyrimicline derivatives 83-84 after elimination of dimethylamine from the (1 1) cycloadducts and oxidative aromatization. This one-pot procedure yielded excellent yields when carried out in the solid state and under microwave irradiation <06BMCL3537>. 

Treating glycosyl isothiocyanates 415 with 5,6-diamino-1,3-dimethyl-uracil (416) gave thioureas 417, which on oxidative cyclization with N-bromosuccinimide afforded 5,7-dioxopyrimido[5,4- ][1,2,4]triazine nucleosides 418 (80MI1 82MI2). 

Azine approach. l,3-Dialkyl-6-hydrazinouradl is susceptible to electrophilic attack at C-5. Treatment of (736 R1 = H) with excess thionyl chloride at room temperature gives the fused uracil (737) in an exothermic reaction. The reaction is thought to involve initial formation of a sulfinyl chloride. Subsequently the electrophilic cyclization occurs at C-5 to form a thiazoline S-oxide which is dehydrated to yield (737). From a,3-dimethyl-6-hydrazinouracil (736 R1 = R3 = Me, R2 = H) the heteroaromatic betaine (738) is formed (78JOC1677). 

Cycloaddition between electron rich 6-[(dimethylamino)methylene]amino-l,3-dimethyl uracil and various electron deficient substrates gave pyrido[2,3-i pyrimidine derivatives in a high regiospecific manner. The pyrido[2,3-i pyrimidinones 17 and their N-oxides 18, 5-deaza-5,8-dihydropterins 19 and pyrido[2,3-i (]pyrimidinone 20 were synthesized from 6-aminouracils, 6-hydroxyaminouracils, 2,6-diaminopyrimidin-4-one and 6-amino-l,3-dimethyl-5-formyluracil, respectively " . ... 

Mn02 in dimethyl sulfoxide at 100° was the best reagent found for oxidation of 5-hydroxyuracil (8) to uracil-5-aldehyde (9). The ratio of substrate to reagent was 1 5. The yield dropped to 40-60% with water as the medium.41 No difference was noted between Attenburrow, Wiley and Irick, or commercial reagent. 

Dimethyl-1-a-D-ribofuranosylbenzimidazole 5-Acetyl-l-(3,5-0-isopropylidene-) -D-xylofuranosyl)uracil 2,3 -Didehydro-[5-methyl-2//-l,2,6-thiadiazin-3yl 4,6-di-O-acetyl-2,3-dideoxy-a-L-eryt/iro-hexopyranoside] 1,1 -di-S-oxide 3,1 -anhydro-[2-(4,6-di-0-acetyl-2,3-dideoxy-a-L-eryt/iro-hexopyranose-3-yl)-3-hydroxy-5-methyl-2if-l,2,6-thiadiazine] 1,1-dioxide ... 

Cycloaddition between electron-rich 6-[(dimethylamino)methylene]amino-1,3-dimethyl uracil 242 and various electron-deficient substrates such as quinones 243 and coumarins 244 was considered to take place by elimination of dimethyla-mine from the respective cycloadducts, followed by oxidative aromatization in a highly regiospecific manner to give pyrido[2,3-solvent-free conditions, the times were reduced to 6-7 min and the yields were increased from 70-80% to 85-94% (04SL1179). 

The hitherto difficultly accessible pyrazolo[4,3-step synthesis from 6-(bromomethyl)-l,3-dimethyl-5-nitro-uracils (259) (Scheme 61). Condensation in ethyl acetate at 0"C allows isolation of the alkylamino-intermediates (261), which in boiling ethanol cyclize to the N-oxides (260). 

---