Methyl-6-hydroxypyrimidine

IV-Isopropyl-3-hydroxyoxindole, see Propachlor 2,3-Isopropylidenedioxyphenol, see Bendiocarb Ispropylisocyanate, see Iprodione 2 Isopropyl-4-methyl-6-hydroxypyrimidine, see Diazinon... 

Plant Diaziuou was rapidly absorbed by and translocated in rice plants. Metabolites identified in both rice plants and a paddy soil were 2-isopropyl-4-methyl-6-hydroxypyrimidine (hydrolysis product), 2-(l -hydroxy-l -methyl)ethyl-4-methyl-6-hydroxypyrimidine, and other polar compounds (Laanio et al, 1972). Oxidizes in plants to diazoxon (Laanio et al., 1972 Ralls et al, 1966 Wolfe et al., 1976) although 2-isopropyl-4-methylpyrimidin-6-ol was identified in bean plants (Kansouh and Hopkins, 1968) and as a hydrolysis product in soil (Somasundaram et al., 1991) and water (Suffet et al., 1967). Five d after spraying, pyrimidine ring-labeled C-diazinon was oxidized to oxodiazinon which then hydrolyzed to 2-isopropyl-4-methylpyrimidin-6-ol which, in turn, was further metabolized to carbon dioxide (Ralls et al, 1966). Diazinon was transformed in field-sprayed kale plants to hydroxydiazinon 0,0-diethyl-0-[2-(2 -hydroxy-2 -propyl)-4-methyl-6-pyrimidinyl] phosphorothioate which was not previously reported (Pardue et al., 1970). 

Diazinon begins to decompose at a temperature of 100 °C. During distillation procedures at this temperature, <0.5% is decomposed to 2-isopropyl-4-methyl-6-hydroxypyrimidine. When technical diazinon is dissolved in 20% hydrochloric acid, 0,0,0-triethyl thiophosphate is formed (Gysin and Margot, 1958). Above 120 °C, diazinon decomposes and emits toxic fumes of phosphorus, nitrogen, and sulfur oxides (Sax and Lewis, 1987 Lewis, 1990 Wlndholz et al, 1983). 

In excess water under acidic conditions, diazinon is hydrolyzed to 2-isopropyl-4-methyl-6-hydroxypyrimidine and diethylthiophosphoric acid. With insufficient water, tetraethyl monothiopyrophosphate is formed (Sittig, 1985). 

The crude product is best purified by sublimation under reduced pressure (100-110°/1 mm.) (recovery 90-95%). Purification can also be effected by recrystallization from acetone (recovery 80-90%), ethyl acetate (recovery 70-80%), or ethanol (recovery 60-70%). The purified 4-methyl-6-hydroxypyrimidine melts at 148-149°. 

The 4-methyl-6-hydroxypyrimidine is surprisingly volatile, and loss of product may occur if the material is heated on the steam bath for an appreciable period of time. 

Methyl-6-hydroxypyrimidine can be prepared by heating 2,6-dichloro-4-methylpyrimidine with red phosphorus and hy-driodic acid 8 and by treating 2-thio-6-methyluracil with hydrogen peroxide.6 The present synthesis is modeled after the work of Brown,3 who has described the desulfurization of several thiopyrimidines. 

Desulfurization is useful in the synthesis of heterocycles where the desired ring system can be constructed most readily in the form of a suKhydryl derivative. An example is the synthesis of 4-methyl-6-hydroxypyrimidine via2-thio-6-methyluracil. The crude thio derivative was desulfurized with 45 g. (wet paste) of Raney nickel. 

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). 

B. 4-Methyl-6-hydroxypyrimidine. To a hot solution of 10 g. (0.07 mole) of 2-thio-6-methyluracil in 200 ml. of distilled water and 20 ml. of concentrated aqueous ammonia in a 500-ml. round-bottomed flask is added 45 g. (wet paste) of Raney nickel catalyst (Note 3). About 30 ml. of distilled water is used to wash all the nickel catalyst into the reaction flask. The mixture is heated under reflux in a hood for about 1.5 hours. The catalyst is permitted to settle, and the clear solution is decanted and filtered by gravity. The catalyst is washed with two 75-ml. portions of hot water and is discarded (Note 4). The combined filtrate and washings (Note 5) are evaporated to dryness on a steam bath. The residue is placed in an oven at 70° to complete the drying process (Note 6). The yield of crude pyrimidine, m.p. 136-142°, is 7.0-7.2 g. (90-93%). 

Thio-6-methyluracil. Furfural Nickel Copper chromiuln oxide 100 0 4-Methyl-6-hydroxypyrimidine 3... 

The reported half-life in soil is 32 days (Jury et al., 1987). Reported half-lives in soil following incubation of 10 ppm diazinon in sterile sand loam, sterile organic soil, nonsterile sandy loam and nonsterile organic soil are 12.5, 6.5, <1 and 2 weeks, respechvely (Miles et al., 1979). The reported half-life of diazinon in sterile soil at pH 4.7 was 43.8 days (Sethunathan and MacRae, 1969). Major metabolites identified were diethyl thiophospho-ric acid, 2-isopropyl-4-methyl-6-hydroxypyrimidine and carbon dioxide (Konrad et al., 1967). When soil is sterilized, the persistence of diazinon increased more so than changes in soil moisture, soil type or rate of application (Bro-Rasmussen et al., 1968). The half-lives for diazinon in flooded soil incubated in the laboratoiy ranged from 4 to 17 days with an average half-life of 10 days (Sethunathan and MacRae, 1969 Sethunathan and Yoshida, 1969 Laanio et al., 1972). The mineralization half-life for diazinon in soil was 5.1 years (Sethunathan and MacRae, 1969 Sethunathan and Yoshida, 1969). 

Chemical/Physical. In water, diazinon is hydrolyzed following first-order kinetics forming 2-isopropyl-4-methyl-6-hydroxypyrimidine and diethyl thiophosphoric acid or diethyl phosphoric acid in the pH range 3.1 to 10.4. At pH values of 7.4 and 10.4, the persistence of diazinon is 185 and <6 days, respectively (Gomaa et al., 1969). Cowart et al. (1971) reported a half-life of approximately 2-3 weeks in a neutral solution at room temperature. Chapman and Cole (1982) reported the following hydrolysis half-lives of diazinon in a sterile 1% ethanol/water solution at 25°C 0.45, 2.0, 7.8, 10 and 7.7 weeks at pH values of 4.5,5.0,6.0,7.0 and 8.0, respectively. Diazoxon was also found infogwater collected near Parlier, CA (Glotfelty et al., 1990). 

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