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Aerobic Oxidation/Annulation Cascades through Synergistic Catalysis of RuCl 3 and N‐Heterocyclic Carbenes
Author(s) -
Wang Qian,
Chen Jiean,
Huang Yong
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201803254
Subject(s) - carbene , catalysis , chemistry , yield (engineering) , annulation , transition metal , ruthenium , synergistic catalysis , metal , combinatorial chemistry , medicinal chemistry , organic chemistry , materials science , metallurgy
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. RuCl 3 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.