4.Dimethylaminopyrimidine and its
2-chloro-, 2-dimethylamino-, 6-chloro-, 6-methylthio-, and
6-dimethylamino-derivatives are quaternized by methyl iodide at N 1. The
structures of the resulting methiodides are proven by alkaline degradation to
known oxopyrimidines. 4-Dimethylamino-2-(and 6-)methoxypyrimidine and
2-dimethylamino-4-methoxypyrimidine all undergo quaternization on a nuclear
nitrogen atom followed by spontaneous loss of methyl iodide to yield
oxopyrimidines (cf. the so-called Johnson and Hilbert nucleoside synthesis).
The unique lability of the dimethylamino group in these quaternary compounds is
exemplified in the con- version of
2-dimethylamino-1,6-dihydro-1,3-dimethyl-6-oxopyrimidinium iodide into
1,3-dimethyluracil by mere dissolution in water or aqueous ethanol, and by the
reaction of 2,4-bisdimethylamino-I-methylpyrimidinium iodide with ethanolic
sodium hydrogen sulphide to give 4-dimethylamino-1,2-dihydro-1-methyl-2-thio-
pyrimidine.
Improved synthesis of SV2A targeting radiotracer [11C]UCB-J