title: Nickel(0)-catalyzed enantioselective annulations of alkynes and arylenoates enabled by a chiral NHC ligand: efficient access to cyclopentenones.
abstract: Cyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel-catalyzed reductive [3+2] cycloaddition of α,β-unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1-symmetric N-heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.
authors.affiliation: Laboratory of Asymmetric Catalysis and Synthesis, EPFL SB ISIC LCSA, BCH 4305, CH-1015 Lausanne (Switzerland) http://isic.epfl.ch/lcsa.
authors.forename: Joachim S E
authors.initials: JS
authors.lastname: Ahlin
authors.forename: Pavel A
authors.initials: PA
authors.lastname: Donets
authors.forename: Nicolai
authors.initials: N
authors.lastname: Cramer
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003517:Cyclopentanes / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D003517:Cyclopentanes; D008024:Ligands; D009532:Nickel; C013905:cyclopentenone
keywords: annulation; asymmetric catalysis; carbenes; cyclopentenones; nickel