Aerobic Oxidation/Annulation Cascades through Synergistic Catalysis of RuCl3 and N‐Heterocyclic Carbenes. Issue 49 (2nd August 2018)

• Record Type: Journal Article
• Authors: Wang, Qian; Chen, Jiean; Huang, Yong
• Is Part Of: Chemistry. Volume 24:Issue 49(2018)
• Page Start: 12806
• Page End: 12810
• Publication Date: 2018-08-02
• Subjects: cooperative effects -- N-heterocyclic carbenes -- oxidation -- ruthenium -- synergistic catalysis; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201803254
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Cooperative catalysis combining a transition metal with an N‐heterocyclic carbene is challenging due to strong binding of NHCs towards late transition metals. We report the first example of synergistic catalysis by a chiral NHC and a coordinatively unsaturated ruthenium compound. RuCl3 was found to mediate efficient aerobic oxidation of homoenolates generated from enals and the N‐heterocyclic carbene. The resulting α, β‐unsaturated acylazolium intermediate reacts selectively with 1, 3‐dicarbonyl compounds or ketones at either the β‐ or γ‐carbon, yielding polysubstituted chiral lactones in high yield and with excellent enantioselectivity (up to 98 % yield, 94 % ee ). This protocol can be applied to structurally sophisticated substrates. Abstract : Polysubstituted chiral lactones are obtained through synergistic catalysis combining NHC and a coordinatively unsaturated Ru III species. This catalyst system enables efficient aerobic oxidation of a homoenolate intermediate, which can be tethered to either a nucleophile or an electrophile to deliver (3+3) and (4+2) annulation products, respectively.