%0 Journal Article
%T Hydropyrimidines. II. Observations on Selective Hydrogenation of Some Hydroxypyrimidines
%A Ga£¿pert
%A B.
%A £¿kari£¿
%A V .
%A £¿kari£¿
%A £¿.
%J -
%D 1964
%X Sa£¿etak Contrary to the generally accepted principle that selective reduction of pyrimidines occurs art the ~5 £¿ 6 position, the partial hydrogenation of 2-hydroxypyrimidine (I) over Adams' catalyst in ethanol was shown to afford 3,6-dihydro-2-hydroxypyrimidine (II). Upon subsequent reduction 3,4,5,6-tetrahydro-2-hydroxypyrimidine (III) was obtained. In order to ascertain the structure of the dihydro compound structurally unambiguous 1-methyl-2-oxopyrimidine (IV) was subjected to the same partial hydrogenation. The NMR spectra of so obtained dihydro-1-methyl-2-oxopyrimidine (V) and the corresponding tetrahydro derivative VI, in particular the chemical shifts of their methyl groups (n 7.08 and 7.06 resp.), complied with the requirements for a 3,6-dihydro compound. 4-Hydroxypyrimidine (IX) did not react with hydrogen under the above mentioned conditions. However, very slow reduction to 1,2,3,6-tetrahydro-4-hydroxypyrimidine . (X) occured with rhodium on carbon as catalyst. On the other h and rhodium on carbon was shown to be very active for reduction of 3-methyl-4-oxopyrimidine (XII) yielding 1,2,3,6-tetrahydro-3-methyl-4-hydroxypyrimidine (XIII). In this series the isolation of dihydro derivatives failed
%U https://hrcak.srce.hr/index.php?show=clanak&id_clanak_jezik=305893