Michael additions azomethine ylides, 1,3-dipolar cycloadditions

MichaeU-Henry Reaction Liu et al. and Xie et al. independently found that tertiary amine-thioureas could stereoselectively promote the addition of diethyl a-aminomalonate-derived azomethine ylides to nitroolefms, affording Michael adducts other than dipolar cycloaddition adducts as the major products. Using monofunctional chiral thioureas 140d instead of tertiary amine-thiourea catalysts, Liu et al. successfully developed a three-component [3-1-2] dipolar cycloaddition of benzaldehydes 3, diethyl a-aminomalonates 45a, and nitrostyrenes 165, resulting directly in the enantioenriched pyrrolidines 208 as the only products (Scheme 2.56) [81a] while Xie et al. efficiently converted the Michael adducts 210 to pyrrolidines 208 in high yield and maintained ee by the use of 30 equiv of 2,2,2-trifluoroethanol as the additive (Scheme 2.56) [81b]. 

The competition between Michael addition and 1,3-dipolar cycloaddition has been investigated for the reaction of alkylidene bisphosphates and alkylidene malonates PhCH=CX2 [X = P(0)(0R)2 or CO2R] with azomethine ylides (generated from PhCH=NCH2C02Me) catalysed by the CuOTf-BiphamPhos complex. ... 

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