Abstract The syntheses of methyl 4-(4-nitrophenyl)-3-oxomorpholine-2-carboxylate (3a) and ethyl 4-(4-nitrophenyl)-2-oxomorpholine-3-carboxylate (5b), important building blocks for the synthesis of factor Xa inhibitor rivaroxaban analogs with potential dual antithrombotic activity, via Rh 2 (OAc) 4-catalyzed O [BOND] H and N [BOND] H carbene insertion reactions are described.
