Calixarene-based chiral primary amine thiourea promoted highly enantioselective asymmetric Michael reactions of α,α-disubstituted aldehydes with maleimides

Recent applications of chiral calixarenes in asymmetric catalysis

“…We also employed calixarene-based chiral primary amine thioureas 47a and 47b in the enantioselective Michael addition of α,α-disubstituted aldehydes 51 to maleimides 52 ( Scheme 14 ) [ 50 ]. The reactions proceeded under mild conditions to give high yields (up to 99%) and ees (up to 98%) with broad substrate scope.…”

Catalytic Access to Succinimide Products Containing Stereogenic Quaternary Carbons

“…For example, diversification of the α‐branched aldehyde, e . g ., to an unsymmetrical aldehyde (R≠R’, Figure ) leads to enantioenriched quaternary carbons, yet the examples are small in number and generally lack high dr . Regarding the maleimide partner, olefin substituted variants (R’’’=alkyl or aromatic, Figure ) have not been reported, and the maleimide nitrogen atom is invariably N‐ Ph functionalized.…”

Design, synthesis and application of chiral tetraoxacalix[2]arene[2]triazine‐based organocatalysts in asymmetric Michael addition reactions

“…[10][11][12][13] The asymmetric Michael addition of ketones, involving α-enolizable ketones to electron deficient nitroolefins has received much attention. [16][17][18] Because of the increasing interest in this area, a wide range of highly efficient chiral organocatalysts have appeared in the literature for asymmetric Michael additions since Barbas and List independently reported the first organocatalytic studies using L-proline. These adducts play an important role as chiral building blocks and can be easily transformed to several functional groups including oximes, amines, hydroxylamines, nitrile oxides, aldehydes, ketones, and carboxylic acids.…”

“…These adducts play an important role as chiral building blocks and can be easily transformed to several functional groups including oximes, amines, hydroxylamines, nitrile oxides, aldehydes, ketones, and carboxylic acids. [16][17][18] Because of the increasing interest in this area, a wide range of highly efficient chiral organocatalysts have appeared in the literature for asymmetric Michael additions since Barbas and List independently reported the first organocatalytic studies using L-proline. 19,20 The common examples include chiral pyrrolidine-type diamines, 21,22 chiral guanidines, 23,24 L-proline derivatives, 25,26 chiral diamines, 27,28 Cinchona-based catalysts, 29,30 urea and thiourea-derived bifunctional organocatalysts.…”