Azetidinone compound and process for preparation thereof

An .alpha.-halopropionamide compound of the formula [II]:

• ##STR78## wherein Ring B is a benzene ring which may be substituted by one to four group(s) selected from the group consisting of a halogen atom, a lower alkyl group, a lower alkoxy group and an aryl group, X is an oxygen atom or a sulfur atom, Y is an oxygen atom, a sulfur atom, a methylene group or an imino group which may be substituted by a lower alkyl group, an acyl group or an aralkyloxycarbonyl group, Z is a methylene group which may be substituted by one to two group(s) selected from the group consisting of a C.sub.3-7 alkylene group, a C.sub.1-20 alkyl group, a C.sub.4-7 cycloalkyl group (said alkylene group, alkyl group and cycloalkyl group being further optionally substituted), an aryl group, an aralkyl group and a heterocyclic group, and L.sup.0 is a halogen atom, or a salt thereof.