Enantioselective [4+2] cycloaddition reaction of α,β-unsaturated imine and methyl vinyl ketone catalyzed by chiral phosphine
作者:Ge Wang、Rukeya Rexiti、Feng Sha、Xin-Yan Wu
DOI:10.1016/j.tet.2015.04.076
日期:2015.6
New bifunctional phosphines were prepared as chiral organocatalysts for the enantioselective [4+2] cycloaddition between α,β-unsaturated imines and methylvinylketone. In the presence of 10 mol % of amide-phosphine, the [4+2] cycloaddition reaction was achieved in good-to-excellent yields (up to 95%) and diastereoselectivities (up to 99:1 dr) with moderate-to-good enantioselectivities (up to 82% ee)
An Upstream By-product from Ester Activation via NHC-Catalysis Catalyzes Downstream Sulfonyl Migration Reaction
作者:Runfeng Han、Liwenze He、Lin Liu、Xingang Xie、Xuegong She
DOI:10.1002/asia.201500959
日期:2016.1
A sequential reaction combining N‐heterocyclic carbene (NHC) and N‐hydroxyphthalimide (NHPI) catalysis allowed for the upstream by‐product NHPI, which was generated in the NHC‐catalyzed cycloaddition reaction, to act as the catalyst for a downstream nitrogen‐to‐carbon sulfonylmigrationreaction. Enantiomeric excess of the major product in the cycloaddition reaction remained intact in the follow‐up
unexpected and efficient dominoreaction of N-sulfonyl-1-aza-1,3-dienes with 2-halo-1,3-dicarbonyl compounds to synthesize differently substituted 2,3-dihydrofuran derivatives with excellent regio-, chemo-, and stereoselectivity in moderate to good yields was developed. In this transformation, broad substrate scope was demonstrated, and a plausible mechanism for this novel dominoreaction was given.
Switchable Access to Different Spirocyclopentane Oxindoles by N-Heterocyclic Carbene Catalyzed Reactions of Isatin-Derived Enals and N-Sulfonyl Ketimines
fused spirocyclopentane oxindoles with four contiguousstereocenters, including twoquaternary carbon centers, was developed. Alternatively, spirocyclopentane oxindoles containing an enaminone moiety can be achieved using the same starting materials, isatin‐derived enals, and N‐sulfonyl ketimines, in the presence of a slightly different NHC catalytic system. This switchable annulation strategy enables
Enantioselective Activation of Stable Carboxylate Esters as Enolate Equivalents <i>via</i> N-Heterocyclic Carbene Catalysts
作者:Lin Hao、Yu Du、Hui Lv、Xingkuan Chen、Huishen Jiang、Yaling Shao、Yonggui Robin Chi
DOI:10.1021/ol300676w
日期:2012.4.20
The first N-Heterocyclic Carbene (NHC) mediated activation of stable carboxylate esters to generate enolate intermediates is disclosed. The catalytically generated arylacetic ester enolates undergo enantioselective reactions with α,β-unsaturated imines.