4-Hydroxypyrimidine, formation

Alkoxides are usually more difficult to hydrolyze than halides, although hydrolysis can be rapid in activated systems. Pyrimidinethiones can sometimes be hydrolyzed directly to pyrimidinones, but it is often better to convert the thiones into alkylsulfenyl, alkylsulfmyl, or alkylsulfonyl derivatives before hydrolysis <1994HC(52)1, 1996CHEC-II(6)93>. The formation of 5-hydroxypyrimidines is not normally performed using hydrolytic procedures, although it can be achieved by the oxidation of boronate species in aqueous solution <1996CC2719, 2006TL7363>. 

The NMR and UV spectra of the aforementioned adducts in DMSO solution decay after some time and are eventually replaced by the spectra of the conjugate bases of the corresponding hydroxypyrimidines. The lower the stability of the adduct, the more effectively the demethylation reaction appears to compete with adduct formation. 

The examples discussed above refer to adduct ion formation, where covalent bonds are formed in the Cl plasma. However, with the increasing importance of alternative ionization techniques, such as thermospray (TSI) and, in particular, electrospray ionization (ESI), a wealth of non-covalent ion/molecule adduct ions can be generated and studied nowadays. One recent example concerns the formation of ion/solvent adducts, [M- -So]+, with M including 3-aminophenol, 3-(methylamino)phenol and 3-(dimethylamino)phenol, and several hydroxypyrimidines, among other aromatic molecules. The relative abundances of ions [M- -H]+, [M -h So -h H]+ and [M - - 2 So - - H]+ were studied as a function of the temperature and the pH, with the solvents being mixtures of methanol/water and acetonitrile/water which may contain ammonium acetate as an additive . Quite in contrast to this empirical study on proton-bound ion/molecule complexes, the non-covalent, open-shell adduct ions [l + -h NH3] were investigated with respect to their intrinsic reactivity. These adduct ions were generated from phenol and ammonia by laser ionization of a... 

The same isomer formation has been observed with the cyclization products of 2-hydrazino-4-methylpyrimidine, 2-hydrazino-4-methyl-6-hydroxypyrimidine, 2-hydrazino-4-phenylpyrimidine and 2-hydrazino-5,6,7,8-tetrahydroquinazoline (316, 320) (Table 10). 

Formation of 2-isopropyl-6-methyl-4-hydroxypyrimidine by chemical hydrolysis of diazinon in soils has been reported earlier (1, 10, 12), The initial step in diazinon degradation in soils appeared to be chemical hydrolysis principally (I, 9, 10) and soil microflora attack the products of the chemical reaction, the pyrimidine and diethyl-thiophosphoric acid, rather than intact diazinon (23). Based on these results, Kearney and Helling (29) in their review on reactions of pesticide in soils included hydrolysis of diazinon as a clear example for chemical transformation of pesticide in soil. In contrast, the data summarized here demonstrated the rapid biological hydrolysis of diazinon molecule which occurs when... 

In 1993 Undheim and co-workers reported the Pd(0)-catalyzed extrusion of CO2 from the arbonate of Scheme 36. This reaction is similar to the formation of allyl aryl ethers by extrusion of CO2 from aUyl aryl carbonates (Scheme 31). However, allylation at nitrogen instead of at oxygen oceurs here. The nucleophilic conjugate base of 2-hydroxypyrimidine or 2-pyrimidin-2-one is an ambident nucleophile (N versus O). 

McLaren 60) observed inhibition of flavin synthe by uracil and ascribed this phenomenon to a competitive inhibition. Goodwin and Pend-lington 52) confirmed the inhibition with large amounts of uracil (50 mg or more N per 100 ml) however, only a slight inhibition of adenine-stimulated flavin production was obtained. Brown el al. 68) observed that 4,5,6-triaminopyrimidine inhibited growth and flavin synthesis of E. ashbyii, while 4,5,6-triamino-2-hydroxypyrimidine and 8-azaxanthine inhibit flavin formation but have little effect on growth. 

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