Asymmetric cyclopropanation of chalcones using chiral phase-transfer catalysts
作者:Richard Herchl、Mario Waser
DOI:10.1016/j.tetlet.2013.02.095
日期:2013.5
The first phase-transfer catalyzed cyclopropanation reaction of chalcones using bromomalonates as the nucleophiles in a Michael Initiated Ring Closing reaction (MIRC) was developed. Key to success was the use of a free OH-containing cinchona alkaloid ammonium salt catalyst and carefully optimized liquid/liquid reaction conditions. The reaction performed well for electron neutral and electron deficient chalcones giving the products in yields up to 98% and with enantiomeric ratios up to 91:9. (C) 2013 Elsevier Ltd. All rights reserved.
Enantioselective Michael Addition of Malonates to Chalcone Derivatives Catalyzed by Dipeptide-derived Multifunctional Phosphonium Salts
HighlyenantioselectiveMichaeladdition of malonates to enones catalyzed by dipeptide-derived multifunctional phosphonium salts has been developed. The newly established catalytic system was characterized with its wide substrate scope featured with aliphatic aldehyde-derived enones and substituted malonates. The gram scale-up synthesis of adducts can also be successfully achieved under optimal conditions