6-ALKYL-2-METHOXY-4(3H)-PYRIMIDINONES AND 5,6-DIALKYL-2-METHOXY-4(3H)-PYRIMIDINONES IN THE TRANSFORMATIONS OF PYRIMIDINES - CONVERSION INTO 2-SUBSTITUTED "AMINO-CHLORO-PYRIMIDINE-DERIVATIVES AND 4-CHLORO-PYRIMIDINE-DERIVATIVES