Asymmetric Synthesis of ß-Indolyl Cyclopentanones and Cyclopentylamides with an All-Carbon Quaternary Stereocenter via Chiral Phosphoric Acid Catalyzed Friedel-Crafts Alkylation Reactions.

The asymmetric Friedel-Crafts alkylation reactions of indoles with ß-substituted cyclopentenimines enabled by chiral phosphoric acid catalysis has been developed, which affords adducts possessing an all-carbon stereocenter with high levels of enantioselectivities. Furthermore, the addition products could be readily converted into two types of useful but previously challenging chiral building blocks, such as ß-alkyl-ß-indolyl cyclopentanones and ß-alkyl-ß-indolyl cyclopentylamides, in one pot via in situ hydrolysis or reduction without erosion of chiral information.