Compounds of formula (I) may be made by reacting an amine of the formula R6 NH2 (III) with a compound of general formula (IV) ##STR4## wherein one of the groups R6 and R7 represents the group R1 R2 NAlkQX(CH2)n Y(CH2)m - and the other represents the group R3, and P is a leaving group such as halogen, thioalkyl (preferably thiomethyl) or alkoxy.