Simple a,p-Unsaturated Compounds

Subsequently, the same group developed an AFC reaction of 4,7-dihydroindoles with a,p-unsaturated aldehydes promoted by diphenyl-prolinol ether (S)-118 in the presence of 20 mol% of triethylamine as the co-catalyst. C2-Substituted 4,7-dihydroindoles 119 were obtained in high yields (61-93%) and excellent enantioselectivity (up to 99% ee). After 

Subsequently, Feng and co vorkers found that /, N -dioxides-Y(OTf)3 complex could catalyze AFC alkylation of indoles with p-trichloro(trifluoro)methyl arylenones 129 (Seheme 6.55). The reaction provided a series of functionalized indoles 130 with a ehiral tertiary earbon center bearing a trichloro(trifluoro) methyl group in exeellent results (up to 99% yield and 96% ee). 

In 2009, You and co orkers reported an intramolecular AFC alkylation of indolyl enones by chiral phosphoric acid. With 5 mol% of (S)-13b, the intramolecular AFC reaction proceeded well, affording the tetrahydropyrano[3,4-Z ] 

The slightly decreased enantioselectivity observed during sequential catalysis was likely due to the formation of racemic product induced by the Ru complex. Notably, the AFC reaction facilitated the cross-metathesis reaction by converting the metathesis product into an alkylation product to drive the equilibrium of the metathesis reaction, as supported by the observation that the cross-metathesis reaction between 135 and 136 led to 133 in only moderate yield in the absence of chiral phosphoric acid. 

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Catalytic enantioselective Friedel-Crafts type addition reactions of electron-rich arenes (indoles, pyrroles etc.) with Michael acceptors have been well developed in the past years. These reactions generally are enabled by chiral Lewis acids or organocatalysts (Scheme 6.24). Chiral Lewis acid-catalyzed processes usually require bidentate substrates (chelating a,p-unsatu-rated compounds) for strong chelation activation. Monodentate compounds (simple a,p-unsaturated compounds) prove to be less selective. With chiral... 

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