Aerobic Oxidation/Annulation Cascades through Synergistic Catalysis of RuCl<sub>3</sub>
and N-Heterocyclic Carbenes
作者:Qian Wang、Jiean Chen、Yong Huang
DOI:10.1002/chem.201803254
日期:2018.9.3
Cooperative catalysis combining a transition metal with an N‐heterocyclic carbene is challenging due to strong binding of NHCstowards 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
Chiral N-heterocycliccarbenecatalyzed annulations of ynals and enals with 1,3-dicarbonyls have been described. The two reactions provided direct and efficient methods for enantioselective synthesis of functionalized dihydropyranones. Comparatively, the reactions starting from ynals were atom-economical; furthermore the reactions of enals demonstrated broader substrate compatibility.
N-Heterocyclic Carbene-Catalyzed Enantioselective Annulation of Bromoenal and 1,3-Dicarbonyl Compounds
作者:Fang-Gang Sun、Li-Hui Sun、Song Ye
DOI:10.1002/adsc.201100622
日期:2011.11
Highly enantioselective [3+3] annulation reactions of bromoenals and 1,3-dicarbonylcompounds are reported. In addition, both enantiomers of the resultant dihydropyranone could be easily obtained by choosing N-heterocyclic carbenes (NHCs) with the same stereocenter but different substituents under the optimized reaction conditions.
Enantioselective<i>N</i>-Heterocyclic Carbene-Catalyzed Michael Addition to α,β-Unsaturated Aldehydes by Redox Oxidation
作者:Zi-Qiang Rong、Min-Qiang Jia、Shu-Li You
DOI:10.1021/ol201595f
日期:2011.8.5
Enantioselective N-heterocyclic carbene-catalyzed Michael addition reactions to α,β-unsaturated aldehydes by redox oxidation were realized. With 10 mol % of camphor-derived triazolium salt D, 15 mol % of DBU, 5 mol % of NaBF4, and 100 mol % of quinone oxidant, the reactions of various dicarbonyl compounds with α,β-unsaturated aldehydes led to 3,4-dihydro-α-pyrones in good yields and excellent ee’s
Divergent NHC-Catalyzed Oxidative Transformations of 3-Bromoenal: Selective Synthesis of 2<i>H</i>-Pyran-2-ones and Chiral Dihydropyranones
作者:Gang Wang、Xia Chen、Gaohan Miao、Weijun Yao、Cheng Ma
DOI:10.1021/jo400950j
日期:2013.6.21
A selectivesynthesis of either 2H-pyran-2-ones (4) or chiral dihydropyranones (6) from the same substrates of 3-bromoenals and 1,3-dicarbonyl compounds upon oxidative N-heterocyclic carbene catalysis is presented. It is shown that the oxidative transformation of 3-bromoenals under NHC catalyst can be well controlled to proceed through two pathways, i.e., elimination of reducible β-bromide or by an