Synthesis of alkyl N-(4-nitrophenyl)-3/2-oxomorpholine-2/3-carboxylates by rhodium(II) acetate catalyzed O–H and N–H carbene insertion

The synthesis of methyl N-(4-nitrophenyl)-3-oxomorpholine-2-carboxylate and ethyl N-(4-nitrophenyl)-2-oxomorpholine-3-carboxylate, via rhodium(II) acetate catalyzed intermolecular O–H and intramolecular N–H carbene insertion, is described. The products represent new and versatile building blocks for the synthesis of bioactive compounds of pharmaceutical interest.