Cyclisation of a compound of formula XII ##STR10## wherein Z.sup.1, Z.sup.2 and Z.sup.3 have the meaning defined in formula I and Q is a hydroxyl, alkoxy or an optionally substituted amino group, a halogen atom, or a RCO.sub.2 group, aROCO.sub.2 group or a RSO.sub.3 group wherein R is alkyl or aryl.