A compound represented by the general formula, ##STR25## R.sub.1 and R.sub.2, which may be the same or different, are a hydrogen atom, a halogen atom, a lower alkyl group, a trifluoromethyl group, a lower alkoxyl group, a lower alkenyloxy group or a halogenated lower alkoxyl group, or are, taken together, a methylenedioxy group;
- R.sub.3 is a vinyl group or a ethynyl group;
- R.sub.4 is a hydrogen atom or a lower alkyl group;
- R.sub.5 is a hydrogen atom or a fluorine atom;
- R.sub.6 is a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxyl group or a trifluoromethyl group;
- Z is a nitrogen atom or a group represented by the formula --CH.dbd.;
- when Z is a nitrogen atom, Y is an oxygen atom;
- and when Z is a group of the formula --CH.dbd., Y is an oxygen atom, a sulfur atom, a methylene group or a group represented by the formula --NH--.