Pyrimidine derivatives and related compounds. Part 48. Uracil ring transformation: conversion of 5-nitrouracils into 5-carbamoyluracils

Abstract

Disubstituted 5-nitrouracils (1 ) react with malonamide in ethanolic sodium ethoxide to afford 1 -substituted 5-carbamoyluracils ( 3 ) via rearrangement of the N (3)-C(4)-C(5) portion of the uracil. This ring transformation has been applied to the preparation of 2',3',5'-tri-0-acetyI-5-carbamoyluridine (8) -Uracils can be converted into pyrazolone (a) and isoxazolone (b) by the reaction with hydrazine and hydroxylamine, re~pectively.~ These reactions involve the direct displacement of the N(l)-C(2)-N(3) portion of the uracil by the N-N or N-0 portion of 1,2-ambident nucleophiles. We have already reported the conversion of 1,3-disubstituted uracil derivatives into other pyrimidines ( c ) ~ and into pyridines (d)5 involving the displacement of the N(l)-C(2)-N(3) portion of the uracils by the N-C-N and C-C-N portion of 1,3-ambident nucleophiles, respectively.

Kost-Sagitullin Rearrangement and Other Isomerization Recyclizations of Pyrimidines. (Review)

“…Such a transformation could take place as a result of cleavage of the N-C(7) bond of the pyrimidine ring followed by cyclization with attack at the C (4) atom of the azole.…”

Novel route for construction of a triazine ring

“…In place of the expected rearrangement product including the pyrazole fragment (compound 3), we basically obtained a bicyclic compound which we identified as ethyl (4-methyl-7-phenylpyrazolo[1,5-a][1, 3,5]triazin-2-yl)acetate (4). We note that a series of recylizations have been reported in the literature which include so called "degenerative rearrangements" of pyrimidines which occur through the substitution of a three-atom pyrimidine fragment with the three-atom fragment from another reagent [3][4][5][6][7][8][9]. As a result, recyclization of pyrimidines to a pyridine or other, novel pyrimidine derivative occurs.…”