Tandem Functionalization of Nonactivated Alkenes and Alkynes in Intramolecular N-Acyloxyiminium Ion Carbocyclization. Synthesis of 6-Substituted Hydroindole 2-Carboxylic Acids
2004-12-09T00:00:00Z (GMT) by
Five-membered N-Boc acyliminium ions derived from l-pyroglutamic acid harboring 4-butenyl and 4-butynyl tethers undergo Lewis acid-mediated halo and tandem Friedel−Crafts carbocyclization within minutes at −78 °C to give stereodefined 6-substituted octahydroindole and hexahydroindole 2-carboxylic acid methyl esters, respectively. The cyclic vinyl bromides are excellent substrates for Pd-catalyzed Suzuki−Miyaura, Heck, and Stille couplings. The method also provides access to enantiopure sp2- and sp3-arylated azabicyclics that are novel and versatile scaffolds for chemical diversification.