2-hydryl-2-(-methyl)--propanoyl fluoride as a useful building block for the synthesis of trifluoromethylated heterocyclic compounds. Synthesis of 1,3-dimethyl-2,3-dihydro-5-(-methyl)-6-fluoro-2-thioxo-4(1H)-pyrimidinone and 1,3-dimethyl-5-(-methyl)-6-fluoro-2,4(1H, 3H)-pyrimidinedione