4- Hydroxy-2 -pyrimidinone

Pyrimidinones have been extensively investigated because of their importance in the chemistry of natural products. Initially, the infrared spectra of the hydroxypyrimidines were interpreted to favor their existence in the hydroxy form ° however, in 1952 Short and Thomp-goniso reinvestigated these compounds and concluded that pyrimidin-2- and -4-one probably exist in the oxo form. Solid-state infrared spectra were used in this early work which probably accounts for the difficulties encountered in their interpretation. Brown and his asso-... 

QinTOuraci and Derivatives 5-Diazouracil 5-Diazo-2,4-pyrimidinediol or 5-Diazo-4-hydroxy-2(1 H)-pyrimidinone (called 5-Diazo-uracil 5-Diazo-2.4-dioxo-tetrahydro-pyrimidin or 5"Diazo-2.4-dioxy-pyriinidin in Ger),... 

Highly activated rings are hydroxylated by K2S208-FeS04 2-pyridone and 3-hydroxypyridine are both hydroxylated para to the substituent thus, each gives the same compound (5-hydroxy-2-pyridone). 2-Pyrimidinone affords the 5-hydroxy derivative. Addition of hydrogen peroxide to the... 

This reaction was extended to prepare 7-nitro- and 9-nitro derivatives of pyrido[l,2-a]pyrimidinone 119 (R = N02, R1 = H R = H, R1 = N02) when the appropriate starting material 118 was heated in boiling dichloro-methane in the presence of triethylamine or when it was stirred in aqueous sodium hydroxide at 20°C (92AJC1825) or treated with sodium azide in aqueous tetrahydrofuran (92AJC2037). Semiempirical molecular orbital calculations (AMI) indicated that the 2-hydroxy-4-oxo tautomeric forms 119 are more stable than the alternative 4-hydroxy-2-oxo tautomeric forms. 

Leszczynski et al. have shown interest in comparing experimental (matrix isolation) and calculated (B3LYP) IR data (frequency and intensity) to discuss the tautomerism of benzo-annelated pyridonone, pyrazinone, and pyrimidinone (144-148). These equilibria were well reproduced by theoretical calculations carried out at the QCISD and QCISD(T) levels. The combined experimental and theoretical results reveal links between aromaticity and tautomerism. Moreover, a UV-induced phototautomeric reaction transforming the oxo forms into the hydroxy tautomers was observed for all (except 3-hydroxyisoquinoline) studied compounds [144], The interest of Leszczynski in problems related to tautomerism, aromaticity, and proton transfer is also apparent in a study of (lH-aza-hetero-2-ylidene)-acetaldehyde and 2-azahetero-2-yl-ethanol tautomeric pairs [145],... 

Yamaguchi, M., K. Wakasugi, R. Saito, Y. Adachi, Y. Yoshikawa, H. Sakurai, and A. Katoh. 2006. Syntheses of vanadyl and zinc(II) complexes of 1-hydroxy-4,5,6-sub-stituted 2(l//)-pyrimidinones and their insulin-mimetic activities. J. Inorg. Biochem. 100 260-9. 

In the photometric determination of copper, a coupling product formed between the diazonium salt from 2-amino-pyridine and resorcinol, or 4-(2-pyridinylazo)-l,3-benzenediol 21, has been used. Here the formed copper complex under acetate buffer exhibits an absorption peak at 520 nm, which is measured photometrically <2003KPU28>. Similarly for photometric determination of iron(ll), a coupling product formed between the diazonium salt of 2-amino-4,6-dihydroxypyrimidine and 8-hydroxyquinoline, or 6-hydroxy-2-(8-hydroxy-7-quinolinyl)azo-4(l//)-pyrimidinone 22, has been used. This reagent forms a blue complex with iron(n) ions with an absorption maximum at 625 nm that does not interfere with the presence of other metals <2003KD95>. 

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