The present invention relates to novel heterocyclic compounds having the general formula (1) ##STR1## wherein: X.sub.1 and X.sub.2 are independently O, S or Se;Y.sub.1 and Y.sub.2 are independently C or N with the proviso that at least one of Y.sub.1 and Y.sub.2 is N;Y.sub.3 and Y.sub.4 are independently C or N with the proviso that at least one of Y.sub.3 and Y.sub.4 is N;R.sub.1 and R.sub.2 each represent one or more groups independently selected from H, lower alkyl, lower alkoxy-lower alkyl, hydroxy-lower alkyl, lower acyloxy-lower alkyl or CF.sub.3 ;and A is ##STR2## geometrical and optical isomers and racemates thereof where such isomers exist, as well as pharmaceutically acceptable acid addition salts thereof and solvates thereof;having therapeutic activity, processes and intermediates for their preparation, pharmaceutical formulations containing said compounds and the medicinal use of said compounds.