Metal-free diastereoselective construction of bridged ketal spirooxindoles via a Michael addition-inspired sequence.

A TfOH-catalyzed highly diastereoselective Michael addition/ketalization sequence of 3-hydroxyoxindoles and ortho-hydroxychalcones was developed, leading to biologically important bridged ketal spirooxindoles in moderate to excellent yields. Moreover, some chemical transformations were carried out to further extend the structural complexity and diversity.

A Copper-Catalyzed Friedel-Crafts Alkylation/Cyclization Sequence: an Approach to Functionalized Pyrrolo[1,2-a]indole Spirooxindoles and 9H-Pyrrolo[1,2-a]indoles.

An efficient Cu(OTf)2-catalyzed Friedel-Crafts alkylation/cyclizaiton sequence of 3-substituted indoles with isatin-derived oxodienes was developed, and a series of structurally complex and diverse pyrrolo[1,2-a]indole spirooxindoles were first obtained in up to 99% yields. This protocol proved to be quite general and was also robust for the synthesis of 9H-pyrrolo[1,2-a]indoles.