77094-88-3Relevant articles and documents
Action de l'hydroxyuree sur des γ-diesters
Bennouna, Chakib,Petrus, Francoise,Verducci, Jean
, p. 478 - 480 (2007/10/02)
We have already shown in earlier papers that hydroxyurea is an interesting synthetic tool.This compound, in reverse to hydroxylamine, reacts in Michael additions or in nucleophilic substitutions only through the oxygen atom.After studying the reaction of hydroxyurea with α-halogenated esters, we wish to report here its reaction with polyfunctional compounds such as dimethyl dibromosuccinate, bromofumarate, bromomaleate and acetylenedicarboxylate.In basic medium, the first step of the reaction of hydroxyurea on dimethyl 2,3-dibromosuccinate results in an elimination of hydrogen bromide and formation of dimethyl bromofumarate; the final products are 5-carbomethoxy-3-hydroxyisoxazole, dimethyl bromofumarate and dimethyl ureidoxymaleate; the yields for the first two compounds depend on the reaction time and on the nature of the base, but the last one is always obtained in trace quantities.Similar results are obtained by the reaction of hydroxyurea with dimethyl bromofumarate and bromomaleate in a typical Michael addition leading to the dimethyl 2-bromo-2-ureidoxysuccinate (not isolable), which, by losing a mole of hydrogen bromide, gives a small quantity of dimethyl ureidoxymaleate (which does not cyclize) and dimethyl ureidoxyfumarate (which cyclizes immediately to 5-carbomethoxy-3-hydroxyisoxazole).The same intermediate, a dimethyl ureidoxyfumarate, was isolated in the case of the reaction of hydroxyurea with dimethyl acetylenecarboxylate.Following a discussion of the various possibilities of dimethyl ureidoxyfumarate cyclization, a rational interpretation of the results is proposed.
