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. [ABSTRACT FROM AUTHOR]