Metal‐Free ipso‐Halocyclization of N‐arylpropynamides Using Hypervalent Iodine(III) Reagents under Aqueous Condition

We report, an intramolecular ipso-halocyclization of N-arylpropynamides using readily available hypervalent iodine reagent as mild oxidant and alkali halides like KCl, KBr, and KI as the halogen source. Using this method, a broad range of valuable halogenated spiro[4.5]trienones can be obtained in an excellent yield at room temperature. Notably, this protocol doesn’t require para-substituents such as methoxy or fluoro group on the N-aryl ring. Also, this reaction takes place in the absence of any metal catalyst under aqueous conditions and exhibits a broad substrate scope with high functional group tolerance. A plausible reaction mechanism is proposed based on control experiments.