A novel and recyclable catalyst, a C3-symmetrical cinchonine-squaramide, has been developed for the asymmetric Michaeladdition of 1,3-dicarbonylcompounds to nitroalkenes. When using only 1 mol% of catalyst 1a for the reaction, high reaction yields with excellent enantioselectivities and diastereoselectivities (up to 96% yield,>99% ee,>99:1 dr) were achieved, in which the results for cyclic keto esters
Supported and Unsupported Chiral Squaramides as Organocatalysts for Stereoselective Michael Additions: Synthesis of Enantiopure Chromenes and Spirochromanes
作者:José M. Andrés、Jorge Losada、Alicia Maestro、Patricia Rodríguez-Ferrer、Rafael Pedrosa
DOI:10.1021/acs.joc.7b01177
日期:2017.8.18
Novel supported chiral bifunctional squaramides have been easily prepared starting from diamines derivedfrom natural amino acids and commercially available aminoalkyl polystyrene resins. These squaramides behave as excellent stereoselective recoverable organocatalysts in different Michael additions, in neat conditions at room temperature. The reaction on 2-(2-nitrovinyl) phenol as electrophile lead
Hydrogen bonding mediated enantioselective organocatalysis in brine: significant rate acceleration and enhanced stereoselectivity in enantioselective Michael addition reactions of 1,3-dicarbonyls to β-nitroolefins
作者:Han Yong Bae、Surajit Some、Joong Suk Oh、Yong Seop Lee、Choong Eui Song
DOI:10.1039/c1cc13637b
日期:——
Brine provides remarkable rateacceleration and a higher level of stereoselectivity over organic solvents, due to the hydrophobic hydration effect, in the enantioselectiveMichael addition reactions of 1,3-dicarbonyls to beta-nitroolefins using chiral H-donors as organocatalysts.
Our findings on the bifunctional squaramide‐catalyzed enantioselective conjugateaddition of β‐ketoamides to nitroolefins are disclosed. It appears that simple acyclic methylene β‐ketoamides, unlike the extensively studied β‐ketoesters, afford the products in excellent diastereoselectivities, and maintain high yields and enantioselectivities. Moreover, competition and kinetic studies were conducted