A compound of the formula: ##STR1## wherein R.sub.1 and R.sub.2 are each a lower alkyl group or they may together represent a lower alkylene group so as to form a nitrogen-containing cyclic group with the nitrogen atom to which they attach, R.sub.3 is a cycloalkyl(lower)alkyl group, an oxacycloalkyl(lower)alkyl group or a dioxacycloalkyl(lower)alkyl group and n is an integer of 0 to 2, which is useful as a herbicide.