Using electron-rich or electron-poor N-substituted oxazolidines as substrates, selective formation of either ammonium or oxonium ylides is possible in the presence of α-imino carbenes. As such, treatment of 5-membered oxazolidine precursors with N-sulfonyl-1,2,3-triazoles under dirhodium catalysis (2 mol%) affords the regiodivergent synthesis of either 8-membered 1,3,6- or 1,4,6-oxadiazocines upon the initial N or O reactivity with the carbene.