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Synthesis of Cyclic Hydroxamic Acids through −NOH Insertion of Ketones

“…This success with cyclobutanone encouraged the application of this sequence to more substituted, less volatile cyclobutanones (Scheme ). A standard two-step sequence of a 2 + 2 cycloaddition between an alkene and dichloroketene followed by Zn/AcOH reduction of the α,α-dichloro ketone intermediate generates various substituted cyclobutanone substrates (Scheme ). , Treatment of these cyclobutanones with Piloty’s acid (2 equiv) in base forms the corresponding cyclic hydroxamic acids in 30−59% yield ( 4 − 7 , Scheme ). The decreased volatility of the substituted cyclobutanone substrates (compared to cyclobutanone) and the decreased water solubility of the products likely improve the isolated yields and facilitate purification.…”