Issue 6, 1984

β-Ureido acids and dihydrouracils. Part 15. Effect of allylic strain on ring opening of 1,6-disubstituted dihydrouracils

Abstract

The rate profiles for the alkaline hydrolysis of some dihydrouracil and dihydro-orotic acid derivatives have been measured in order to assess the effect of allylic strain on the ring opening of 1,6-disubstituted dihydrouracils. The introduction of a 1-nitrogen-substituent in the 6-substituted compounds brings about a substantial decrease (40–500 times) in the observed rate constant which is second order in hydroxide ion (k1k3/k–1). The rate decreases of the addition step, k1, are moderate and in the range expected from the observed shifts in conformational equilibria towards the axial conformation which gives rise to a hindered transition state. The major contributions to the rate decreases arise from the ring-opening step, k3/k–1, and have been attributed to strains of the type associated with the gem-dimethyl effect upon ring closure.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1984, 1077-1081

β-Ureido acids and dihydrouracils. Part 15. Effect of allylic strain on ring opening of 1,6-disubstituted dihydrouracils

A. H. Koedjikov, I. B. Blagoeva, I. G. Pojarlieff and E. J. Stankevic, J. Chem. Soc., Perkin Trans. 2, 1984, 1077 DOI: 10.1039/P29840001077

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