Novel processes for preparing 2-chlorothiazoles, useful as an intermediate for insecticides, from allyl isothiocyanate derivatives having the formula [II]: ##STR1## wherein X represents a leaving group, are simple and convenient reaction procedures under mild conditions without need of a large excess of a chlorinating agent. Further, processes for preparing 5-(aminomethyl)-2-chlorothiazole or salts thereof from the compound [II] achieve higher yields by simple, convenient and inexpensive procedures.