Pyrimidine reactions. XIII. The conversion of simple alkoxy- and alkylthiopyrimidines into butylaminopyrimidines

Abstract

The formation of 2- and 4-butylaminopyrimidine from simple alkoxy- and alkylthio-pyrimidines with butylamine in the absence of added solvent has been followed either spectrometrically or by gas chromatography. The apparent first- order rate constants indicate that each 4- substituted pyrimidine reacts more slowly than its 2-isomer; each alkylthiopyrimidine more slowly than its alkoxy analogue; and the higher homologues more slowly than the parent methoxy or methylthio homologues. All such reactions are considerably slower than those involving the corresponding chloropyrimidines. Rates have been measured also for the thermal rearrangement of 4-methoxypyrimidine into 1,6- dihydro-1-methyl-6-oxopyrimidine, in the presence of triethylamine and other bases. These data permit allowances for simultaneous rearrangement to be made in the rate constants of appropriate aminolyses.