title: Copper-catalyzed propargylic substitution of dichloro substrates: enantioselective synthesis of trisubstituted allenes and formation of propargylic quaternary stereogenic centers.
abstract: An easy and versatile Cu-catalyzed propargylic substitution process is presented. Using easily prepared prochiral dichloro substrates, readily available Grignard reagents together with catalytic amount of copper salt and chiral ligand, we accessed a range of synthetically interesting trisubstituted chloroallenes. Substrate scope and nucleophile scope are broad, providing generally high enantioselectivity for the desired 1,3-substitution products. The enantioenriched chloroallenes could be further transformed into the corresponding trisubstituted allenes or terminal alkynes bearing all-carbon quaternary stereogenic centers, through the copper-catalyzed enantiospecific 1,1/1,3-substitutions. The two successive copper-catalyzed reactions could be eventually combined into a one-pot procedure and different desired allenes or alkynes were obtained respectively with high enantiomeric excesses.
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4 (Switzerland), Fax: (+41) 22-379-32-15.
authors.forename: Hailing
authors.initials: H
authors.lastname: Li
authors.forename: David
authors.initials: D
authors.lastname: Grassi
authors.forename: Laure
authors.initials: L
authors.lastname: Guénée
authors.forename: Thomas
authors.initials: T
authors.lastname: Bürgi
authors.forename: Alexandre
authors.initials: A
authors.lastname: Alexakis
keywords: Grignard reagents; P ligands; allenes; asymmetric catalysis; copper