Reactions of Nitrosobenzenes with Cyclobutanones by Activation with a Lewis Acid

Abstract

Formal [4+2] cycloaddition between 3-ethoxy-2-alkylcyclobutanones and nitrosobenzene proceeded by activation with Me3SiOTf to afford 6-alkyl-2-phenyl-2H-1,2-oxazin-5(6H)-one by regioselective cleavage of the more substituted C2–C3 bond of the cyclobutanone ring. On the other hand, reactions of 3-phenylcyclobutanones and 2-benzyloxycyclobutanone with nitrosobenzene gave γ,δ-unsaturated and cyclic hydroxamic acid derivatives, respectively, by cleavage of a cyclobutanone C1–C2 bond.