Nickel(0)-Catalyzed Enantioselective Annulations of Alkynes and Arylenoates Enabled by a Chiral NHC Ligand: Efficient Access to Cyclopentenones

• Published in: Angewandte Chemie International Edition 2014-11, Vol.53 (48), p.13229-13233
• Main Authors: Ahlin, Joachim S. E., Donets, Pavel A., Cramer, Nicolai
• Format: Article
• Language: English
• Subjects: Alkynes; Alkynes - chemistry; annulation; asymmetric catalysis; Asymmetry; Carbenes; Catalysis; Catalysts; Cycloaddition; Cyclopentanes - chemistry; cyclopentenones; Esters; Ligands; Molecular Structure; nickel; Nickel - chemistry; Stereoisomerism; Synthesis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201408364

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. Cyclization: Nickel(0) catalysts with a chiral bulky C1‐symmetric N‐heterocyclic carbene ligand enabled the efficient asymmetric reductive [3+2] cycloaddition of enoates and alkynes, providing substituted cyclopentenones under mild conditions. The system provided the products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.