Tandem functionalization of nonactivated alkenes and alkynes in intramolecular N-acyloxyiminium ion carbocyclization. Synthesis of 6-substituted hydroindole 2-carboxylic acids.
[reaction: see text] 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 degrees 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.
Hanessian
Stephen
S
Department of Chemistry, Université de Montréal, C.P. 6128, Station Centre-ville, Montréal, PQ, H3C 3J7 Canada. stephen.hanessian@umontreal.ca
Tremblay
Martin
M