Zinc Mediated Direct Transformation of Propargyl N-hydroxylamines to α,β-Unsaturated Ketones and Mechanistic Insight.

A Lewis acid catalyzed direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones in the presence of aqueous Zn(II)-salts has been described. This investigation also provides a novel observation for the stoichiometric role of Zn-halides over what is known to date for catalytic processes. A thorough mechanistic study has been established based on the experiment using 18O-labeled water in optimized reaction conditions; the incorporation of 18O in the desired product was also substantiated by HRMS. This methodology is also a mild, inexpensive, and an efficient approach for this unusual conversion.