5- Fluoro-l,3-dimethyluracil

Thiol anions normally add reversibly to uracil derivatives <1991T4361>, although stable adducts can be isolated when the intermediate enolate is trapped with an added electrophile <2006JHC1095>. Thus, the addition of lithium phenylthiolate to 5-fluoro-l,3-dimethyluracil 457 in the presence of benzaldehyde gave a 46% yield of the adduct 458 as a mixture of only two diastereomers <2006JHC1095>. 

Some oxidations of heterocyclcs with two heteroatoms proceed very readily. Thus, fluorinated quinazoline is oxidized to quinazol-4-one on fusing for only 2 minutes (Table 16).264 On the other hand, more vigorous oxidation of 5-fluoro-l,3-dimethyluracil by 3-chloroperoxybenzoic acid leads to the formation of unstable intermediate radicals that tend to rearrange to 4-hy-droxy-l,3-dimethylimidazoledione 3-chlorobenzoate (Table 16), similar177 to the chemical behavior of trifluoromethylated phenol.265... 

The photochemical reactions of 6-chloro- and 5-fluoro-l,3-dimethyluracils with naphthalene and selected substituted derivatives in solvents of varying protic and polarity characteristics are the subject of three reports within the review period. " Irradiation of the chloro derivative and naphthalene in cyclohexane or benzene afforded exclusively the substituted product (35), whereas in... 

Irradiation of 5-fluoro-l,3-dimethyluracil and various benzophenones gives rise to mixtures of oxetanes and [2 -f 2] uracil dimers. The product ratios (oxetanes to dimers) depend on the henzophenone triplet energy levels. Kinetic analysis shows that the rate constants of the two processes are comparable. When 5-fluoro-l,3-dimethyluracil is irradiated in the presence of methoxy- and dimethoxy-naphthalene derivatives, selective formation of conjugated (arylpropenylidene)-l,3-diazin-2-ones is observed, through a pathway involving an initial Paterno-Biichi photocyclisation. ... 

The isomer distribution for 5-ArDMU s was analogous to those typically observed in aromatic photosubstitution reactions. On the other hand, few reports have appeared on the meta-oriented aromatic photosubstitution reaction, the primary example being the photoinduced proton exchange in benzenes that proceeds via an electrophilic aromatic photosubstitution reaction. In the case of either the 5-chloro-or 5-fluoro-l,3-dimethyluracil (5-ClDMU, 5-FDMU), > addition of TFA simply promoted 5-arylation (photo-Friedel-Crafts reaction), while the addition of a bromide (p-dibromobenzene, 1,2-dibromoet-hane, benzyl bromide, HBr) to the solution induced the meta-oriented 6-arylation (Scheme 2)."... 

Seki, K. and Ohkura, K., Acid-catalyzed photosubstitution of 5-fluoro-l,3-dimethyluracil with substituted benzenes. Nucleosides Nucleotides, 11, 521,1992. 

Pyrimidine-2,4(1//,3//)-dione (uracil) does not react with 7V-fluorobis(trifluoromethylsul-fonyl)amine (Id) at 22 C in acetic acid, probably due to its insolubility, but when heated at 45 CC for 12 hours it gives a difluorinated acetoxy derivative which could not be isolated.114 1,3-Dimethyluracil reacts with two equivalents of 1 d at 22 °C to give 6-acetoxy-5,5-difluoro-l, 3-dimethyl-5,6-dihydrouracil in 85% yield while with one equivalent of Id 5-fluoro-l, 3-dimethyl-uracil (mp 132-134°C) is also obtained.114... 

Removal of the 2 -sulfonyloxy group of 859 in a basic medium, followed by reaction with metal halides (LiBr and Nal) or hydrogen halides (HCl-1,4-dioxane, HBr-acetone, or0.1% HFin l,4-dioxane-AlF3)gave, byway of the 2,2 -anhydro intermediate 861, the 2 -halo derivatives 862-865. The 2 -deoxy analog 866 and l-(6-deoxy-6-fluoro- ff-D-mannopyranosyl)thy-mine were also prepared from 864 (R = H) and 861 (R = H), respectively. l-(4-Deoxy-4-fluoro-y -D-glucopyranosyl)thymine was obtained by the condensation method. A different kind of nucleoside, 5-(5-deoxy-5-fluoro-2,3-0-isopropylidene-a-D-ribofuranosyl)-l,3-dimethyluracil has also been prepared. ... 

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