Enantioselective Cyclopropanation of Indoles: Construction of All-Carbon Quaternary Stereocenters

The first enantioselective copper-catalyzed cyclopropanation of <i>N</i>-acyl indoles is described. Using carbohydrate-based bis(oxazoline) ligands (<i>gluco</i>Box), the products were obtained in up to 72% ee. Cyclopropanation of <i>N</i>-Boc 3-methyl indole yielded a product with an all-carbon quaternary stereocenter, which is a valuable building block for the synthesis of indole alkaloids: Deprotection and rearrangement gave a tricyclic hemiaminal ester in 96% ee, which was subsequently employed as a key intermediate for the synthesis of (−)-desoxyeseroline