Construction of an all-carbon quaternary stereocenter by organocatalytic enantioselective α-functionalization of α-substituted β-ketocarbonyls with electron deficient vinylarenes
An asymmetric direct aldol reaction of acetoacetals is described. Under the catalysis of a simple chiral primaryamine, the direct aldol reactions of acetoacetals occur exclusively on the γ-position to give vinylogous-type aldol products with high diastereo- and enantioselectivity.
Enantioselective Synthesis of 4<i>H</i>-Pyrans Through Organocatalytic Asymmetric Formal [3+3] Cycloadditions of 2-(1-Alkynyl)-2-alken-1-ones with β-Keto Esters
4H‐Pyran units are frequently present in molecules with significant biological and pharmaceutical activities. Herein, we present the first enantioselective formal [3+3] cycloaddition between 2‐(1‐alkynyl)‐2‐alken‐1‐ones and β‐keto esters catalyzed by a cyclohexyldiamine‐based thiourea‐tertiary amine bifunctional catalyst. Under the mild and eco‐friendly conditions, a wide range of polysubstituted 4H‐pyrans