Synthesis of α-Azidovinyl Ketones from the Iodine Azide Adducts of α,β-Unsaturated Ketones

A synthetic approach to α-azidovinyl ketones is provided by the reaction of the iodine azide adducts of α,β-unsaturated ketones with sodium azide in DMF at room temperature. α-Azidochalcone (3a), α-azidobenzylideneacetone (3b), and α-azidoethyiideneacetophenone (3c) weee prepared in good yields and subsequently converted to the corresponding iminophosphoranes on treatment with triphenylphosphine. The mechanism of the synthetic method, which involves in part transposition of an azide function, is discussed, as is the regiochemistry of IN_a additions to unsaturated carbonyl compounds.