Synthesis of 2‐substituted‐3‐nitroimidazo[1,2‐b]pyridazines as potential biologically active agents

A new heterocyclic reductive alkylating agent, 6‐chloro‐2‐chloromethyl‐3‐nitroimidazo1,2‐b]pyridazine, was synthesized for the first time. It was shown to react under phase‐transfer catalysis conditions with 2‐nitropropane anion by an S_RN1 mechanism to give excellent yield of isopropylidene derivative formed from a base‐promoted nitrous acid elimination of C‐alkylation product. Extension of this S_RN1 reaction to various nitronate anions led to a new class of 3‐nitroimidazo1,2‐b]pyridazine derivatives bearing a trisub‐stituted double bond at the 2‐position.