Methods of alkylating target compounds are disclosed. The alkylating agent can be radiolabeled. In some instances, the alkylating agent is synthesized and then reacted with a target compound without an intervening purification step. The method comprises synthesizing an alkylating agent having the formula:X—(CR1R2)aCR3R4-LGwherein,a is 0, 1, 2 or 3,R1, R2, R3 and R4 are independently H, X or alkyl,X is a halogen or a label, with the proviso that at least one X is a halogen,LG is a leaving group anddirectly reacting said alkylating agent with a target compound comprising an alkylation reactive group under conditions suitable for the alkylation of said target compound.
