Non‐Diazo Approach to Functionalized Hydroxamate Through Formal Reductive O─H Bond Insertion Reaction of Hydroxamic Acids

In this study, an efficient approach is investigated for accessing hydroxamates via the P(III)‐mediated O─H bond insertion reaction of hydroxamic acid with α‐keto esters. The key to success was determined by the in situ generation of Kukhtin–Ramirez adducts, which are useful carbene surrogates, thereby achieving diazo‐, metal‐, and base‐free O─H bond insertion reactions. The mild reaction conditions, excellent functional group tolerance, useful synthetic transformations, and successful modification of drug molecules demonstrate the utility and practicality of this method.