Title
Crown ether derived from d-glucose as an efficient phase-transfer catalyst for the enantioselective Michael addition of malonates to enones
Author
Zsolt Rapi, Alajos Grün, Tamás Nemcsok, Dóra Hessz, Mihály Kállay, Miklós Kubinyi, György Keglevich, Péter Bakó
Year
2016
Journal
Tetrahedron: Asymmetry
Abstract
A monoaza-15-crown-5 lariat ether derived from d-glucose 1 has been applied as a chiral phase-transfer catalyst in the Michael addition of diethyl, dimethyl, diisopropyl and dibenzyl malonates to enones under mild conditions to afford the adducts with good to excellent enantioselectivities. In the reaction of diethyl malonate with substituted trans-chalcone, the adducts with in enantioselectivities up to 89% ee. Among the reactions of substituted diethyl malonates, those of diethyl acetoxymalonate gave the best results (96% ee). The effect of the substituents of the chalcone was also investigated in reactions with diethyl acetoxymalonate. Among the chalcones substituted on the β-aryl, the para-substituted compounds resulted in the highest enantioselectivities (88–97% ee). The substituents on the benzoyl aryl of chalcone caused a decrease in the enantioselectivity compared to the unsubstituted case. The adducts with furyl or thiophenyl substituents were formed with >99% ee. The glucose-based catalyst also proved to be effective in the cases of diisopropyl and dibenzyl acetoxymalonates (including ees up to 99% ee). The reactions of diethyl acetoxymalonate with cyclic enones gave the corresponding Michael adducts with enantioselectivities up to 83%. The absolute configuration of one of the new Michael adducts was determined by CD spectroscopy.
Instrument
J-810
Keywords
Circular dichroism, Absolute configuration, Materials