Compounds of general formula ##STR1## wherein R.sup.1 represents a radical selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an unsubstituted aryl group having 6 carbon atoms, an aryl group having 6 carbon atoms being substituted by at least one radical selected from the group consisting of a chlorine atom, alkyl and alkoxy each having up to 2 carbon atoms; and R.sup.2 represents an alkyl group having from 1 to 6 carbon atoms.
一般式为##STR1##的化合物,其中R.sup.1代表从以下组中选择的基团:1至6个碳原子的烷基基团,6个碳原子的未取代芳基基团,6个碳原子的芳基基团,被至少一个从以下组中选择的基团取代:
氯原子、每个具有最多2个碳原子的烷基和烷氧基;而R.sup.2代表1至6个碳原子的烷基基团。