Convenient Synthesis and Molecular Structures of Diverse Functionalized Polycyclic Spirooxindoles
Mei‐Jun Zhu, Ting Tang, Jing Sun, Chao‐Guo YanABSTRACT
The diverse functionalized polycyclic spirooxindoles were efficiently synthesized by base promoted cyclization reaction of cyclic β ‐enamino esters and MBH carbonates of isatins. Three kinds of MBH carbonates of isatins showed very different reactivity and gave different kinds of polycyclic compounds. A very interesting ring contraction process from six‐membered 3,4‐dihydrobenzo[ b ][1,4]oxazine to 5‐membered 2,3‐dihydrobenzo[ d ]oxazole on spirooxindole skeleton was clearly observed. The relative configurations of the various polycyclic compounds were clearly elucidated by determining several single‐crystal structures.