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Abstract: (Chemical Abstract 1996, 126:46797)
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The reactivity of 6-aminopyrimidin-4(3H)-ones towards DMAD is
successfully explained by theoretical investigation (PM3 semiempirical methods).
All the PM3 results ( activation energies (DE) for the transition
states and the heat of formation (DH) for the products)
support our previous experimental work [J. Cobo et al. Synlett.1993, 4, 297-299;
Tetrahedron 1994, 50, 10345-10354]. In those reactions two main products
were obtained: the pyridine derivatives 5 as major ones, which are formed by a
tandem DA/RDA reaction withextrusion of the methylisocyanate fragment;
and 5-ethenylpyrimidin-4(3H)-ones 10 as minor ones, which arised from a
Michael addition, being incompetition with the above normal DA.
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