354. A new synthesis and the chemical properties of 5-aminopyrimidine

Abstract

Suitable conditions have been determined for the catalytic dechlorination of chloropyrimidines. 5-Aminopyrimidine (I) has been synthesised from uracil, via 5-amino-2 : 4-dichloropyrimidine (I1 ; R = NH,), in 44% over-all yield. The chemical and some physical properties of the former have been examined and a number of derivatives prepared. 5-Aminopyrimidine did not give a diazonium salt, but its dichloro-derivative was converted by nitrous acid into diazouracil (VII) ; the mechanism of this reaction is discussed.

A Novel Practical Synthesis of C‐2‐Arylpurines

“…[18,19] We first tried reaction of 4 with simple aryl organometallics such as aryllithium, aryl-Grignard or milder arylzinc reagents. Unfortunately the reactions with these reagents were not successful, and resulted in only complex mixtures containing small amounts of the desired product and the side product reacted at the C-6 position even when excess amounts of organometallic reagents were used.…”

Polychloroheteroaromatic Compounds

“…It is not possible to convert 5-nitrobarbituric acid into its trichloro-derivative by treatment with phosphorus oxychloride in the presence of NN-dimethylaniline (the reaction proceeds only as far as the 2,4-dichloro-compound) [545], but the reaction proceeds smoothly in the presence of NN-diethylaniline [544]! Trichloro-5-nitropyrimidine may be prepared also by treatment of 4,6-dichloro-2-methylthio-5-nitropyrimidine with chlorine in ethanol (see also ref.…”

“…Pyrimidine was first prepared in this way by reduction of its 2,4,6-trichloro-derivative with zinc dust and water [519]. Higher yields (> 90%) are obtained when the 2,4,6-trichloro-compound [530,545] or the perchlorocompound [530] are hydrodechlorinated over palladium-charcoal in the presence of a suitable base, for example magnesium oxide [545] or sodium hydroxide [530]. In the absence of a suitable base, reduction of the ring also occurs to give 1,4,5,6-tetrahydropyrimidine (ca.…”

Metal‐Free Debromination of 5‐Bromopyrimidine Derivatives Using DMF/Trialkylamine as the Hydrogen Source

“…While vasicine, glucose and thiourea exhibited a great reducing potential over the reduction of nitroarenes, catalyst‐free reduction of carbonyls are mostly limited to the use of hydrazine hydrate and formaldehyde . A literature survey disclosed that halogenated pyrimidines have been reduced in the presence of transition metal catalysts such as palladium, zinc dust as well as by hot hydroiodic acid, p ‐toluenesulphonyl hydrazine and electrolysis at mercury cathodes . Reports on dehalogenation of halo‐uracils mainly involve photochemical reductions through irradiation in aqueous alcoholic solvents, thermolysis in acetamide, sonication in the presence of Indium metal, and reduction under physiological conditions ,.…”