Because certain (2-chloroethy1) triazenes and (2-haloethy1) nitrosoureas have high antineoplastic activity, 2-chloroethyl and 2-fluoroethyl sulfonates were prepared to try to develop additional types of 2-haloethylating agents. In this initial study, it was demonstrated that antineoplastic activity much superior to that of the prototype, 2-chloroethyl methanesulfonate, could be found among 2-chloroethyl sulfonates. Among a variety of 2- ...