5 -Methyl pyrimidine

Although it is seldom used, esterification of pyrimidinecarboxylic acids proceeds normally. Conditions are illustrated by the conversion of pyrimidine-4-carboxylic acid (181 R = H) into its methyl ester (181 R = Me) by methanol/sulfuric acid (47%), methanol/hydrogen chloride (80%), or by diazomethane (ca. 100%) (60MI21300). The isomeric methyl pyrimidine-2-carboxylate is formed by treatment of the silver salt of the acid with methyl iodide. Higher esters, e.g. (182 R = Bu), are usually made by warming the acid (182 R = H) with the appropriate alcohol and sulfuric acid (60JOC1950). 

The aminolysis of esters of pyrimidine occurs normally to yield amides. The reagent is commonly alcoholic ammonia or alcoholic amine, usually at room temperature for 20-24 hours, but occasionally under refiux aqueous amine or even undiluted amine are used sometimes. The process is exemplified in the conversion of methyl pyrimidine-5-carboxylate (193 R = Me) or its 4-isomer by methanolic ammonia at 25 °C into the amide (196) or pyrimidine-4-carboxamide, respectively (60MI21300), and in the butylaminolysis of butyl ttracil-6-carboxylate (butyl orotate) by ethanolic butylamine to give A-butyluracil-5-carboxamide (187) (60JOC1950). Hydrazides are made similarly from esters with ethanolic hydrazine hydrate. 

Chloropyrimidine is aminated with alcoholic ammonia at 130° while 4-chloro-2-methyl- and 4-chloro-6-methyl-pyrimidine yield the corresponding 4-amino derivatives at 100°. 4-Aminopyrimi-dine is not prepared from the chloro analog because of facile self-quatemization (see Section III, B, 2 for comments on factors involved) of the latter. 

Amino-6-methyl pyrimidine p-Acetylaminobenzene sulfonyl chloride Hydrogen chloride... 

To a well agitated solution of 6.95 grams of 2-amino-6-methyl pyrimidine in 40 cc of pyridine, 15 grams of p-acetylaminobenzenesulfonyl chloride are added in small portions over a 30 minute period. The reaction mixture is then heated on a steam bath for 30 minutes, the free pyridine being then removed under reduced pressure and the residue mixed with cold water, and the latter mixture is vigorously stirred. The solid reaction product is removed by filtration and washed with cold water. 

There is obtained a yield of 14 grams of crude 2-(p-acetylaminobenzenesulfonamido)-6-methyl pyrimidine, which on recrystallization from alcohol and water melts at 238° to 239°C. The crude product is hydrolyzed by suspending it in 400 cc of 2 N hydrochloric acid and warming until solution is complete. The solution is neutralized with sodium carbonate and the precipitated 2-(sulfanilamido)-6-methyl pyrimidine is removed by filtration. The latter on recrystallization from alcohol and water shows a melting point of 225° to 226°C. 

Thiamin (3-(4-amino-2-methyl-pyrimidin-5-ylmethyl)-5-(2-hydroxyethyl)-4-methylthiazolium)... 

Methylpyrimidine has been obtained by the present method2 and by a three-step method that begins with the condensation of acetoacetic ester with urea to give 2,6-dihydroxy-4-methyl-pyrimidine the latter is treated with phosphorus oxychloride to give 2,6-dichloro-4-methylpyrimidine, which is reduced by zinc dust and water 8 or by catalytic hydrogenolysis.4... 

Thiamine can be considered to be the product of the quatemization of 4-methyl-5-(2-hydroxymethyl)thiazole (5) by an active derivative of 4-amino-5-(hydroxymethyl)-2-methyl pyrimidine (4) (Scheme 2). In living cells, pyramine can be activated by conversion into the diphosphate 7, via monophosphate 6, and the substrate of the enzyme responsible for the quatemization is not the thiamine thiazole, but its phosphate 8. The product of the condensation, thiamine phosphate (9), is finally converted into diphosphate 2—the biochemically active derivative—by hydrolysis to free thiamine, followed by diphosphorylation, or more directly, in some cases. Enzymes are known for all of the steps depicted in Scheme 2, and adenosine triphosphate (ATP) is, as usual, the phosphate donor. 

The Levafix P dyes have been replaced by the Levafix PN (DyStar) range, which is based on the 5 chloro-2-fluorO 4-methylpyrimidine system. These two systems are essentially similar, but the Levafix PN dyes have a fluorine atom as the labile entity rather than the methylsulphonyl grouping. The necessary intermediate 5-chloro-2,6-difluoro-4-methyl-pyrimidine (7.25) can be made from 4-methyl-2,5,6-trichloropyrimidine by an exchange reaction with potassium fluoride (Scheme 7.20). Condensation with the dye base (Scheme 7.21) will give a mixture of isomers, namely, the 5 chloro-6-fluoro-4-methyl (7.26) and 5-chloro-2-fluoro-4-methyl (7.27) derivatives. 

A variety of other carbon nucleophiles have been alkylated with alcohols including malonate esters, nitroaUcanes, ketonitriles [119, 120], barbituric acid [121], cyanoesters [122], arylacetonitriles [123], 4-hydroxycoumarins [124], oxi-ndoles [125], methylpyrimidines [126], indoles [127], and esters [128]. Selected examples are given in Scheme 35. Thus, benzyl alcohol 15 could be alkylated with nitroethane 147, 1,3-dimethylbarbituric acid 148, phenylacetonitrile 149, methyl-pyrimidine 150, and even f-butyl acetate 151 to give the corresponding alkylated products 152-156. 

A number of papers have reported studies on pyrimidine radical cations. 1-Methylthymine radical cations generated via a triplet-sensitized electron transfer to anthraquinone-2,6-disulfonic acid were detected by Fourier transform electron paramagnetic resonance (FTEPR). The parent 1-methylthymine radical cation, and its transformation to the N(3)-deprotonated radical cation, were observed. Radical cations formed by addition of HO and POs" at C(6) were also detected depending on the pH. Similarly, pyrimidine radical cations deprotonated at N(l) and C(5)-OH were detected from the reaction of 804 with various methylated pyrimidines." These radicals are derived from the initial SO4 adducts of the pyrimidines. Radical cations of methylated uracils and thymines, generated by electron transfer to parent ions of... 

Zur Uberfiihrung von 4-Methyl-pyrimidin zu 3,4-Di-4-pyrimidyl-furazan-2-oxid [73% (als Hy-dronitrat) Schmp. 157° freie Base Schmp. 134°]321. 

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