Doubly stereocontrolled asymmetric conjugate addition of acetylacetone to nitroolefins catalyzed by bifunctional tertiary amine–thiourea catalysts derived from both acyclic α-amino acids and carbohydrates
preparative, cheap, and fine-tunable bifunctional chiral tertiary amine–thiourea organocatalysts have been developed by combining both acyclic diamines derived from acyclic α-amino acids and carbohydrates. These organocatalysts promoted the enantioselective conjugate addition of acetylacetone to various nitroolefins in good yields (up to 93%) with good enantioselectivities (up to 91% ee). The present research
Highly Enantioselective Michael Addition of α-Substituted Cyano Ketones to β,γ-Unsaturated α-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral Dihydropyrans
An asymmetric Michaeladdition of α-substituted cyano ketones to β,γ-unsaturated α-keto esters to form chiral dihydropyrans catalyzed by a series of α-amino acid-derived thiourea-tertiary amines is presented. A novel tyrosine-derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91–95% yields and with 90–96% ee at a low catalyst loading of 2.0 mol%. The utility