Synthesis of no‐carrier‐added radiobrominated N‐alkylated analogues of spiperone

The synthesis of a series of p‐bromo‐3‐N‐alkyl spiperone analogues is described. N‐alkylation was achieved via reaction of the potassium salt of the spiperone lactam ring with alkyl iodide; subsequent reactions with elemental bromine gave the p‐brominated isomers. Optimization studies using no‐carrier‐added (n.c.a.) ⁷⁷Br⁻ indicated that radiobromination of N‐alkyl spiperone analogues occurs with higher yields and in shorter reaction times when dichloramine‐T (DCT) is used rather than H₂O₂/acetic acid as an oxidant. The production of the title compounds in high effective specific activity with radiochemical yields of 20–30 % using n.c.a. ⁷⁷Br⁻ and DCT is reported.