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2005
Fused pyrimidine derivatives
R 0515
Some Aspects of Reaction of 6-Aminouracil and 6-Amino-2-thiouracil with
Ketones. — The reactions of amino derivatives (I) with chalcones
37- 155 α,β-Unsaturated
like (II) are performed in the presence of basic or acidic catalysts or by heating in glacial
acetic acid. The conditions used has influence on the composition of the product mixture consisting of dihydropyridopyrimidines (III) and pyridopyrimidines (IV). Basic
catalysts decrease the yields of (III) whereas acids increase them. Refluxing aminouracils (I) in glacial acetic acid furnishes dihydro derivatives (III) while in other cases
only pyridopyrimidines are isolated. Oxidation of dihydro compounds (III) with NBS
affords sufficiently pure pyridopyrimidines (IV). The three-component reaction of (I)
with precursors of chalcones, (V) and acetophenone, proceeds without participation of
acetophenone. In the presence of strong electron-donor groups, elimination of the aryl
substituent is observed, cf. (VIII). — (CHEBANOV*, V. A.; SARAEV, V. E.; GURA,
E. A.; DESENKO, S. M.; MUSATOV, V. I.; Collect. Czech. Chem. Commun. 70
(2005) 3, 350-360; Inst. Monocryst., Natl. Acad. Sci. Ukraine, Kharkov 61001,
Ukraine; Eng.) — H. Hoennerscheid
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