Highly enantioselective Michael addition of diethyl malonate to chalcones catalyzed by cinchona alkaloids-derivatived bifunctional tertiary amine-thioureas bearing multiple hydrogen-bonding donors
作者:Yulong Liu、Xie Wang、Xiaoyun Wang、Wei He
DOI:10.1039/c4ob00203b
日期:——
Chalcones are still challenge substrates in Michael reactions, and only limited success has been achieved. This work describes a highlyenantioselectiveMichaeladdition of diethyl malonate with chalcones catalyzed by cinchona alkaloids-derivatived bifunctional tertiary amine-thioureasbearingmultiplehydrogen-bondingdonors.
Newtypes of mesitylene based tri-site containing asymmetric quaternary ammonium salts 9a and 9b have been prepared and used as efficient chiral phasetransfercatalysts for enantioselective Michael addition reactions between the chalcones and diethylmalonate under mild reaction conditions such as lower concentration of base, catalyst and ultrasonic conditions with very good chemical yields (up to
enantioselective Michaeladditionreactions of diethyl malonate to various chalcones have been achieved under mild chiral multisite phase-transfer reaction conditions by the successful utilization of 2,4,6-(triscinchoniummethyl)phenyl-1,3,5-triazines as new chiral quaternary ammonium catalysts. This simple asymmetricMichaeladdition process was found to be quite effective and to obtain Michael adducts with