with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
in which said hetero-bound carbon atoms are part of a substructure —C(=X)—X—C(=X)—X— in which X is an oxygen or sulphur atom or an imino radical, e.g. imidoylguanidines
