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.
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
Direct β-Activation of Saturated Aldehydes to Formal Michael Acceptors through Oxidative NHC Catalysis
作者:Junming Mo、Liang Shen、Yonggui Robin Chi
DOI:10.1002/anie.201302152
日期:2013.8.12
mediated by N‐heterocyclic carbenes (NHCs) enables the direct β‐carbon functionalization of saturated aldehydes (see scheme). The reaction proceeds through two sequential oxidative steps to generate α,β‐unsaturated triazolium ester equivalents as formal Michael acceptors, which react with 1,3‐diketones and β‐ketone esters in an enantioselective manner.
Direct Activation of β-sp<sup>3</sup>-Carbons of Saturated Carboxylic Esters as Electrophilic Carbons via Oxidative Carbene Catalysis
作者:Bin Liu、Weihong Wang、Ruoyan Huang、Jiekuan Yan、Jichang Wu、Wei Xue、Song Yang、Zhichao Jin、Yonggui Robin Chi
DOI:10.1021/acs.orglett.7b03650
日期:2018.1.5
An N-heterocyclic carbene-catalyzed oxidative LUMO activation of the β-cabons of saturated carboxylic esters is disclosed. This approach allows for efficient asymmetric access to lactams and lactones by directly installing functional groups to the typically inert β-sp3 carbons of saturated esters. The use of HOBt as an additive was found to significantly improve both yields and enantioselectivities
activation of saturated acid chlorides by oxidative N-heterocycliccarbene catalysis has been successfully utilized to synthesize enantio-enriched spirooxindolelactones and δ-lactones. The reaction involves the transformation of the β sp3 carbon of saturated acid chlorides into an electrophilic carbon as a key step. The product was obtained in excellent yield and stereoselectivity.