Compounds of the formula ##STR1## wherein: R.sub.1 is phenyl or phenyl mono- to tri-substituted by R.sub.4 ; R.sub.2 is hydrogen, C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.5 alkyl substituted by the radical OR.sub.5 or by the radical SR.sub.5, C.sub.3 -C.sub.6 cycloalkyl, C.sub.3 -C.sub.6 cycloalkyl mono- to tri-substituted by C.sub.1 -C.sub.4 alkyl or by halogen, C.sub.2 -C.sub.5 alkenyl, C.sub.2 -C.sub.5 alkynyl or the formyl radical; R.sub.3 is hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkyl substituted by halogen, cyano or by the radical OR.sub.5 or by the radical SR.sub.5, C.sub.3 -C.sub.6 cycloalkyl or C.sub.3 -C.sub.6 cycloalkyl mono- to tri-substituted by C.sub.1 -C.sub.4 alkyl or by halogen; R.sub.4 is halogen; C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.2 haloalkyl, C.sub.1 -C.sub.3 alkoxy or C.sub.1 -C.sub.3 haloalkoxy; R.sub.5 is hydrogen, C.sub.1 -C.sub.5 alkyl, C.sub.3 -C.sub.5 alkenyl, C.sub.3 -C.sub.5 alkynyl or the radical (CH.sub.2).sub.n -X-C.sub.1 -C.sub.3 -alkyl;R.sub.7 is the group -NH.sub.2, ##STR2## and where R.sub.8 -R.sub.11 are as defined hereafter.