ALKYL (E)-2,3-DIBROMOPROPENOATES AND (Z)-2,3-DIBROMOPROPENOATES AS PRECURSORS TO 3-SUBSTITUTED ALKYL (E)-2-BROMOPROPENOATES AND (Z)-2-BROMOPROPENOATES, 2,3-DISUBSTITUTED ALKYL (Z)-PROPENOATES AND (E)-PROPENOATES AND SOME HETEROCYCLIC-COMPOUNDS